Files
ladybird/Libraries/LibJS/Bytecode/AsmInterpreter/asmint.asm
Andreas Kling 928a9dfbf7 LibJS+AsmIntGen: Retire the positional t0..t8 / ft0..ft3 DSL aliases
asmint.asm no longer references any positional temp register name --
every handler and macro declares its temporaries by name with `temp` /
`ftemp` and lets the register allocator place them. Migrate the last
two macros holding out:

  * dispatch_current uses a macro-local `opcode` temp for the load8 +
    indirect jmp.
  * pop_inline_frame_and_resume names its return-pc, dst-index, value-
    address, vm-pointer, and executable temps explicitly.

With nothing left referring to the positional aliases, drop the
tN / ftN -> physical-register fallback from registers::resolve_register
and update the DSL reference comments at the top of asmint.asm and in
main.rs to describe the named-temp model. The two pre-existing codegen
tests that probed the old positional behavior get rewritten to use the
post-allocation physical-register names directly, since that is now
the actual contract of resolve_op.
2026-04-26 13:29:56 +02:00

2791 lines
102 KiB
NASM

# AsmInterpreter DSL source
# Each handler implements one bytecode instruction.
# Instructions not listed here fall through to the C++ fallback handler.
#
# For the full DSL instruction reference, see AsmIntGen/src/main.rs.
#
# Register conventions (pinned in callee-saved regs, survive C++ calls):
# pc = program counter (byte offset into bytecode, 32-bit)
# pb = bytecode base pointer (u8 const*)
# values = pointer to Value[] array (registers+constants+locals+arguments)
# exec_ctx = running ExecutionContext*
# dispatch = dispatch table base pointer (256 entries, 8 bytes each)
#
# Temporary registers are declared by name with `temp` (GPR) and
# `ftemp` (FPR) inside each handler or macro; the register allocator
# assigns them to physical registers from the platform's caller-saved
# pool. None of the temps survive C++ calls (`call_slow_path`,
# `call_helper`, `call_interp`, `call_raw_native`).
#
# NaN-boxing encoding:
# Every JS Value is a 64-bit NaN-boxed value. The upper 16 bits encode the type tag.
# If tag == 0x0000..0xFFF8, the value is a double (IEEE 754 double-precision).
# Otherwise, the tag identifies the type:
# INT32_TAG (0xFFF9) - Lower 32 bits are a sign-extended int32
# BOOLEAN_TAG - Bit 0 = true/false
# UNDEFINED_TAG - undefined (0x7FFE)
# NULL_TAG - null (0x7FFF)
# OBJECT_TAG - Lower 48 bits are a sign-extended Object*
# STRING_TAG - Lower 48 bits are a sign-extended PrimitiveString*
# SYMBOL_TAG - Lower 48 bits are a sign-extended Symbol*
# BIGINT_TAG - Lower 48 bits are a sign-extended BigInt*
# ACCESSOR_TAG - Internal accessor marker
# EMPTY_TAG - Internal empty/hole marker (used for TDZ)
# A double whose exponent+mantissa bits match CANON_NAN_BITS would collide
# with the tag space, so all NaN values are canonicalized to CANON_NAN_BITS.
# The *_SHIFTED constants (e.g. INT32_TAG_SHIFTED, UNDEFINED_SHIFTED) are
# the tag shifted left by 48 bits, used for quick full-value comparisons.
#
# Instruction field references:
# Inside a handler, m_fieldname (e.g. m_dst, m_src, m_lhs) resolves to the
# byte offset of that field within the current handler's bytecode instruction.
# Field offsets are computed from Bytecode.def by the asmintgen compiler.
#
# Handler structure:
# Each handler follows a common pattern:
# 1. Load operands (load_operand)
# 2. Type-check via tag extraction (extract_tag + branch)
# 3. Fast path for int32 and/or double
# 4. Slow path fallback to C++ (call_slow_path)
# call_slow_path is TERMINAL: control does not return to the handler.
# call_helper and call_interp are NON-TERMINAL: the handler continues after.
# NOTE: extract_tag, unbox_int32, unbox_object, box_int32, and
# box_int32_clean are codegen instructions (not macros), allowing each
# backend to emit optimal platform-specific code.
#
# extract_tag dst, src -- Extract upper 16-bit NaN-boxing tag.
# unbox_int32 dst, src -- Sign-extend low 32 bits to 64.
# unbox_object dst, src -- Zero-extend lower 48 bits (extract pointer).
# box_int32 dst, src -- NaN-box a raw int32 (masks low 32, sets tag).
# box_int32_clean dst, src -- NaN-box an already zero-extended int32.
# Check if a value is a double (not a NaN-boxed tagged value).
# All tagged types have (tag & NAN_BASE_TAG) == NAN_BASE_TAG in their upper 16 bits.
# Jumps to fail if not a double.
macro check_is_double(reg, fail)
temp tag
extract_tag tag, reg
and tag, NAN_BASE_TAG
branch_eq tag, NAN_BASE_TAG, fail
end
# Check if an already-extracted tag represents a non-double type.
# Clobbers the tag register. Jumps to fail if not a double.
macro check_tag_is_double(tag, fail)
and tag, NAN_BASE_TAG
branch_eq tag, NAN_BASE_TAG, fail
end
# Check if both values are doubles.
# Jumps to fail if either is not a number tag.
macro check_both_double(lhs, rhs, fail)
temp lhs_tag, rhs_tag
extract_tag lhs_tag, lhs
and lhs_tag, NAN_BASE_TAG
branch_eq lhs_tag, NAN_BASE_TAG, fail
extract_tag rhs_tag, rhs
and rhs_tag, NAN_BASE_TAG
branch_eq rhs_tag, NAN_BASE_TAG, fail
end
# Coerce two operands to numeric types for arithmetic / comparison.
# If both are int32: jumps to both_int_label with lhs_int / rhs_int holding
# the sign-extended 64-bit ints.
# If one or both are double: falls through with lhs_dbl / rhs_dbl holding
# the values as doubles.
# If either is not a number (int32 or double): jumps to fail.
macro coerce_to_doubles(lhs, rhs, lhs_int, rhs_int, lhs_dbl, rhs_dbl, both_int_label, fail)
temp tag
extract_tag tag, lhs
branch_ne tag, INT32_TAG, .lhs_not_int
extract_tag tag, rhs
branch_ne tag, INT32_TAG, .int_rhs_maybe_double
# Both int32
unbox_int32 lhs_int, lhs
unbox_int32 rhs_int, rhs
jmp both_int_label
.int_rhs_maybe_double:
# tag already has rhs tag, known != INT32_TAG
check_tag_is_double tag, fail
unbox_int32 lhs_int, lhs
int_to_double lhs_dbl, lhs_int
fp_mov rhs_dbl, rhs
jmp .coerced
.lhs_not_int:
# tag already has lhs tag, known != INT32_TAG
check_tag_is_double tag, fail
extract_tag tag, rhs
branch_eq tag, INT32_TAG, .double_rhs_int
# tag already has rhs tag, known != INT32_TAG
check_tag_is_double tag, fail
fp_mov lhs_dbl, lhs
fp_mov rhs_dbl, rhs
jmp .coerced
.double_rhs_int:
fp_mov lhs_dbl, lhs
unbox_int32 rhs_int, rhs
int_to_double rhs_dbl, rhs_int
.coerced:
end
# NOTE: canonicalize_nan is a codegen instruction, not a macro.
# canonicalize_nan dst_gpr, src_fpr
# If src_fpr is NaN, writes CANON_NAN_BITS to dst_gpr.
# Otherwise bitwise-copies src_fpr to dst_gpr.
# Box a double result as a JS::Value, preferring Int32 when the double is a
# whole number in [INT32_MIN, INT32_MAX] and not -0.0. This mirrors the
# JS::Value(double) constructor so that downstream int32 fast paths fire.
# dst: destination GPR for the boxed value.
# src_fpr: source FPR containing the double result.
# The macro uses a macro-local temp; the allocator will pick a register
# that doesn't conflict with the caller's live values.
macro box_double_or_int32(dst, src_fpr)
temp int_value
double_to_int32 int_value, src_fpr, .bdi_not_int
branch_zero int_value, .bdi_check_neg_zero
box_int32 dst, int_value
jmp .bdi_done
.bdi_check_neg_zero:
fp_mov dst, src_fpr
branch_negative dst, .bdi_not_int
box_int32 dst, int_value
jmp .bdi_done
.bdi_not_int:
canonicalize_nan dst, src_fpr
.bdi_done:
end
# Shared same-tag equality dispatch.
# lhs_tag is known equal to rhs's tag. For int32, boolean, object, symbol,
# undefined, null: bitwise compare. For string: pointer shortcut, else
# slow. For bigint: always slow. Falls through to .double_compare for
# doubles. The macro destroys lhs_tag (clobbers it during the
# undefined/null check).
macro equality_same_tag(lhs, rhs, lhs_tag, equal_label, not_equal_label, slow_label)
branch_any_eq lhs_tag, INT32_TAG, BOOLEAN_TAG, .fast_compare
branch_any_eq lhs_tag, OBJECT_TAG, SYMBOL_TAG, .fast_compare
branch_eq lhs_tag, STRING_TAG, .string_compare
branch_eq lhs_tag, BIGINT_TAG, slow_label
# Check undefined/null: (tag & 0xFFFE) == UNDEFINED_TAG matches both.
# Safe to clobber lhs_tag here since every other tagged type is
# already routed.
and lhs_tag, 0xFFFE
branch_eq lhs_tag, UNDEFINED_TAG, .fast_compare
# Must be a double
jmp .double_compare
.string_compare:
branch_eq lhs, rhs, equal_label
jmp slow_label
.fast_compare:
branch_eq lhs, rhs, equal_label
jmp not_equal_label
end
# Compare lhs/rhs as doubles with NaN awareness.
# Defines .double_compare label (referenced by equality_same_tag).
macro double_equality_compare(lhs, rhs, equal_label, not_equal_label)
ftemp lhs_dbl, rhs_dbl
.double_compare:
fp_mov lhs_dbl, lhs
fp_mov rhs_dbl, rhs
branch_fp_unordered lhs_dbl, rhs_dbl, not_equal_label
branch_fp_equal lhs_dbl, rhs_dbl, equal_label
jmp not_equal_label
end
# Strict equality check core logic.
# Jumps to equal_label if definitely equal, not_equal_label if definitely
# not, or slow_label if we can't determine quickly. Handles: int32,
# boolean, undefined/null, object, symbol (bitwise compare), string
# (pointer shortcut), bigint (slow), doubles.
macro strict_equality_core(lhs, rhs, equal_label, not_equal_label, slow_label)
temp lhs_tag, rhs_tag, lhs_int
ftemp lhs_dbl, rhs_dbl
extract_tag lhs_tag, lhs
extract_tag rhs_tag, rhs
branch_ne lhs_tag, rhs_tag, .diff_tags
equality_same_tag lhs, rhs, lhs_tag, equal_label, not_equal_label, slow_label
double_equality_compare lhs, rhs, equal_label, not_equal_label
.diff_tags:
# Different tags but possibly equal: int32(1) === double(1.0) is true.
# Handle int32 vs double inline; all other tag mismatches are not equal.
branch_eq lhs_tag, INT32_TAG, .lhs_int32_diff
branch_eq rhs_tag, INT32_TAG, .rhs_int32_diff
# Neither is int32. If both are doubles, compare. Otherwise not equal.
check_tag_is_double lhs_tag, not_equal_label
check_tag_is_double rhs_tag, not_equal_label
jmp .double_compare
.lhs_int32_diff:
check_tag_is_double rhs_tag, not_equal_label
unbox_int32 lhs_int, lhs
int_to_double lhs_dbl, lhs_int
fp_mov rhs_dbl, rhs
branch_fp_equal lhs_dbl, rhs_dbl, equal_label
jmp not_equal_label
.rhs_int32_diff:
check_tag_is_double lhs_tag, not_equal_label
fp_mov lhs_dbl, lhs
unbox_int32 lhs_int, rhs
int_to_double rhs_dbl, lhs_int
branch_fp_equal lhs_dbl, rhs_dbl, equal_label
jmp not_equal_label
end
# Loose equality check core logic.
# Same as strict_equality_core but with null==undefined cross-type handling.
macro loose_equality_core(lhs, rhs, equal_label, not_equal_label, slow_label)
temp lhs_tag, rhs_tag
extract_tag lhs_tag, lhs
extract_tag rhs_tag, rhs
branch_ne lhs_tag, rhs_tag, .diff_tags
equality_same_tag lhs, rhs, lhs_tag, equal_label, not_equal_label, slow_label
double_equality_compare lhs, rhs, equal_label, not_equal_label
.diff_tags:
# null == undefined (and vice versa): (tag & 0xFFFE) == UNDEFINED_TAG
and lhs_tag, 0xFFFE
branch_ne lhs_tag, UNDEFINED_TAG, .try_double
and rhs_tag, 0xFFFE
branch_eq rhs_tag, UNDEFINED_TAG, equal_label
jmp slow_label
.try_double:
check_both_double lhs, rhs, slow_label
jmp .double_compare
end
# Numeric compare with coercion (for jump variants).
# Uses coerce_to_doubles to handle mixed int32+double operands.
# int_cc: signed comparison branch for int32 (branch_lt_signed, etc.)
# double_cc: unsigned comparison branch for doubles (branch_fp_less, etc.)
# Jumps to true_label / false_label / slow_label.
macro numeric_compare_coerce(lhs, rhs, int_cc, double_cc, true_label, false_label, slow_label)
temp lhs_int, rhs_int
ftemp lhs_dbl, rhs_dbl
coerce_to_doubles lhs, rhs, lhs_int, rhs_int, lhs_dbl, rhs_dbl, .both_int, slow_label
branch_fp_unordered lhs_dbl, rhs_dbl, false_label
double_cc lhs_dbl, rhs_dbl, true_label
jmp false_label
.both_int:
int_cc lhs_int, rhs_int, true_label
jmp false_label
end
# Numeric compare without coercion (for non-jump variants).
# Only handles both-int32 or both-double fast paths.
macro numeric_compare(lhs, rhs, int_cc, double_cc, true_label, false_label, slow_label)
temp tag, lhs_int, rhs_int
ftemp lhs_dbl, rhs_dbl
extract_tag tag, lhs
branch_ne tag, INT32_TAG, .try_double
extract_tag tag, rhs
branch_ne tag, INT32_TAG, slow_label
unbox_int32 lhs_int, lhs
unbox_int32 rhs_int, rhs
int_cc lhs_int, rhs_int, true_label
jmp false_label
.try_double:
# tag already has lhs tag
check_tag_is_double tag, slow_label
check_is_double rhs, slow_label
fp_mov lhs_dbl, lhs
fp_mov rhs_dbl, rhs
branch_fp_unordered lhs_dbl, rhs_dbl, false_label
double_cc lhs_dbl, rhs_dbl, true_label
jmp false_label
end
# Epilogue for comparison/equality handlers that produce a boolean result.
# Defines .store_true, .store_false, and .slow labels.
macro boolean_result_epilogue(slow_path_func)
temp result
.store_true:
mov result, BOOLEAN_TRUE
store_operand m_dst, result
dispatch_next
.store_false:
mov result, BOOLEAN_FALSE
store_operand m_dst, result
dispatch_next
.slow:
call_slow_path slow_path_func
end
# Epilogue for jump comparison/equality handlers.
# Defines .take_true, .take_false, and .slow labels.
macro jump_binary_epilogue(slow_path_func)
temp target
.slow:
call_slow_path slow_path_func
.take_true:
load_label target, m_true_target
goto_handler target
.take_false:
load_label target, m_false_target
goto_handler target
end
# Coerce two operands to int32 for bitwise operations.
# On success: lhs_int / rhs_int hold the sign-extended int32 values.
# If either operand is not a number (int32, boolean, or double):
# jumps to fail.
macro coerce_to_int32s(lhs, rhs, lhs_int, rhs_int, fail)
temp tag
ftemp fp_scratch
extract_tag tag, lhs
branch_any_eq tag, INT32_TAG, BOOLEAN_TAG, .lhs_is_int
check_tag_is_double tag, fail
fp_mov fp_scratch, lhs
js_to_int32 lhs_int, fp_scratch, fail
jmp .lhs_done
.lhs_is_int:
unbox_int32 lhs_int, lhs
.lhs_done:
extract_tag tag, rhs
branch_any_eq tag, INT32_TAG, BOOLEAN_TAG, .rhs_is_int
check_tag_is_double tag, fail
fp_mov fp_scratch, rhs
js_to_int32 rhs_int, fp_scratch, fail
jmp .rhs_done
.rhs_is_int:
unbox_int32 rhs_int, rhs
.rhs_done:
end
# Fast path for bitwise binary operations on int32/boolean/double operands.
# op_insn: the bitwise instruction to apply (xor, and, or).
macro bitwise_op(op_insn, slow_path_func)
temp lhs, rhs, lhs_int, rhs_int, dst
load_operand lhs, m_lhs
load_operand rhs, m_rhs
coerce_to_int32s lhs, rhs, lhs_int, rhs_int, .slow
op_insn lhs_int, rhs_int
box_int32 dst, lhs_int
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path slow_path_func
end
# Validate that the callee still points at the expected builtin function.
# Jumps to fail if the call target has been replaced or is not a function.
macro validate_callee_builtin(expected_builtin, fail)
temp callee, scratch
load_operand callee, m_callee
extract_tag scratch, callee
branch_ne scratch, OBJECT_TAG, fail
unbox_object callee, callee
load8 scratch, [callee, OBJECT_FLAGS]
and scratch, OBJECT_FLAG_IS_FUNCTION
branch_zero scratch, fail
load8 scratch, [callee, FUNCTION_OBJECT_BUILTIN_HAS_VALUE]
branch_zero scratch, fail
load8 scratch, [callee, FUNCTION_OBJECT_BUILTIN_VALUE]
branch_ne scratch, expected_builtin, fail
end
# Load a UTF-16 code unit from a primitive string with resident UTF-16 data.
# string is the PrimitiveString*; index is the non-negative code-unit
# index; code_unit is the destination GPR for the zero-extended result.
# Jumps to out_of_bounds if index >= string length.
# Jumps to fail if the string would require resolving deferred data.
macro load_primitive_string_utf16_code_unit(string, index, code_unit, out_of_bounds, fail)
temp scratch, utf16_data
load8 scratch, [string, PRIMITIVE_STRING_DEFERRED_KIND]
branch_ne scratch, PRIMITIVE_STRING_DEFERRED_KIND_NONE, fail
load64 utf16_data, [string, PRIMITIVE_STRING_UTF16_STRING]
branch_zero utf16_data, fail
load8 scratch, [string, PRIMITIVE_STRING_UTF16_SHORT_STRING_BYTE_COUNT_AND_FLAG]
and scratch, UTF16_SHORT_STRING_FLAG
branch_zero scratch, .long_storage
load8 scratch, [string, PRIMITIVE_STRING_UTF16_SHORT_STRING_BYTE_COUNT_AND_FLAG]
shr scratch, UTF16_SHORT_STRING_BYTE_COUNT_SHIFT_COUNT
branch_ge_unsigned index, scratch, out_of_bounds
mov code_unit, string
add code_unit, PRIMITIVE_STRING_UTF16_SHORT_STRING_STORAGE
load8 code_unit, [code_unit, index]
jmp .done
.long_storage:
load64 scratch, [utf16_data, UTF16_STRING_DATA_LENGTH_IN_CODE_UNITS]
branch_negative scratch, .utf16_storage
branch_ge_unsigned index, scratch, out_of_bounds
add utf16_data, UTF16_STRING_DATA_STRING_STORAGE
load8 code_unit, [utf16_data, index]
jmp .done
.utf16_storage:
shl scratch, 1
shr scratch, 1
branch_ge_unsigned index, scratch, out_of_bounds
mov code_unit, index
add code_unit, index
add utf16_data, UTF16_STRING_DATA_STRING_STORAGE
load16 code_unit, [utf16_data, code_unit]
.done:
end
# Dispatch the instruction at current pc (without advancing).
# Clobbers t0.
macro dispatch_current()
goto_handler pc
end
# Walk the environment chain using a cached EnvironmentCoordinate.
# Input: m_cache_field is the offset of the EnvironmentCoordinate inside
# the bytecode instruction.
# Output: target_env points at the resolved environment, bind_index holds
# the binding index within it.
# On failure (invalid cache, screwed by eval): jumps to fail_label.
macro walk_env_chain(m_cache_field, target_env, bind_index, fail_label)
temp coord_addr, hops, sentinel, screw
lea coord_addr, [pb, pc]
add coord_addr, m_cache_field
load_pair32 hops, bind_index, [coord_addr, ENVIRONMENT_COORDINATE_HOPS], [coord_addr, ENVIRONMENT_COORDINATE_INDEX]
mov sentinel, ENVIRONMENT_COORDINATE_INVALID
branch_eq hops, sentinel, fail_label
load64 target_env, [exec_ctx, EXECUTION_CONTEXT_LEXICAL_ENVIRONMENT]
branch_zero hops, .walk_done
.walk_loop:
load8 screw, [target_env, ENVIRONMENT_SCREWED_BY_EVAL]
branch_nonzero screw, fail_label
load64 target_env, [target_env, ENVIRONMENT_OUTER]
sub hops, 1
branch_nonzero hops, .walk_loop
.walk_done:
load8 screw, [target_env, ENVIRONMENT_SCREWED_BY_EVAL]
branch_nonzero screw, fail_label
end
# Pop an inline frame and resume the caller without bouncing through C++.
# The asm-managed JS-to-JS call fast path currently only inlines Call, never
# CallConstruct, so caller_is_construct is always false for asm-managed inline
# frames.
#
# This mirrors VM::pop_inline_frame():
# 1. Read the caller's destination register from the callee frame.
# 2. Publish the caller's resume pc and returned value.
# 3. Deallocate the callee by rewinding InterpreterStack::top to exec_ctx.
# 4. Make the caller the running execution context again.
# 5. Advance execution_generation so WeakRef and similar observers still see
# the same boundary they would have seen through the C++ helper.
#
# The macro expects exec_ctx/pb/values/pc to still describe the callee frame.
# Input:
# caller_frame = ExecutionContext* of the caller
# value_reg = NaN-boxed return value
macro pop_inline_frame_and_resume(caller_frame, value_reg)
temp ret_pc, dst_idx, value_addr, vm, exe
load_pair32 ret_pc, dst_idx, [exec_ctx, EXECUTION_CONTEXT_CALLER_RETURN_PC], [exec_ctx, EXECUTION_CONTEXT_CALLER_DST_RAW]
store32 [caller_frame, EXECUTION_CONTEXT_PROGRAM_COUNTER], ret_pc
lea value_addr, [caller_frame, SIZEOF_EXECUTION_CONTEXT]
store64 [value_addr, dst_idx, 8], value_reg
load_vm vm
store64 [vm, VM_RUNNING_EXECUTION_CONTEXT], caller_frame
store64 [vm, VM_INTERPRETER_STACK_TOP], exec_ctx
inc32_mem [vm, VM_EXECUTION_GENERATION]
mov exec_ctx, caller_frame
load64 exe, [exec_ctx, EXECUTION_CONTEXT_EXECUTABLE]
load64 pb, [exe, EXECUTABLE_BYTECODE_DATA]
lea values, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
mov pc, ret_pc
dispatch_current
end
# ============================================================================
# Simple data movement
# ============================================================================
handler Mov
temp value
load_operand value, m_src
store_operand m_dst, value
dispatch_next
end
handler Mov2
temp v1, v2
load_operand v1, m_src1
store_operand m_dst1, v1
load_operand v2, m_src2
store_operand m_dst2, v2
dispatch_next
end
handler Mov3
temp v1, v2, v3
load_operand v1, m_src1
store_operand m_dst1, v1
load_operand v2, m_src2
store_operand m_dst2, v2
load_operand v3, m_src3
store_operand m_dst3, v3
dispatch_next
end
# ============================================================================
# Arithmetic
# ============================================================================
# Arithmetic fast path: try int32, check overflow, fall back to double, then slow path.
# The coerce_to_doubles macro handles mixed int32+double coercion.
# On int32 overflow, we convert both operands to double and retry.
# box_double_or_int32 re-boxes double results as Int32 when possible,
# mirroring JS::Value(double), so downstream int32 fast paths can fire.
handler Add
temp lhs, rhs, lhs_int, rhs_int, dst
ftemp lhs_dbl, rhs_dbl
load_operand lhs, m_lhs
load_operand rhs, m_rhs
coerce_to_doubles lhs, rhs, lhs_int, rhs_int, lhs_dbl, rhs_dbl, .both_int, .slow
fp_add lhs_dbl, rhs_dbl
box_double_or_int32 dst, lhs_dbl
store_operand m_dst, dst
dispatch_next
.both_int:
# 32-bit add with hardware overflow detection
add32_overflow lhs_int, rhs_int, .overflow
box_int32_clean dst, lhs_int
store_operand m_dst, dst
dispatch_next
.overflow:
# Int32 overflow: convert both to double and redo the operation
unbox_int32 lhs_int, lhs
unbox_int32 rhs_int, rhs
int_to_double lhs_dbl, lhs_int
int_to_double rhs_dbl, rhs_int
fp_add lhs_dbl, rhs_dbl
fp_mov dst, lhs_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_add
end
# Same pattern as Add but with subtraction.
handler Sub
temp lhs, rhs, lhs_int, rhs_int, dst
ftemp lhs_dbl, rhs_dbl
load_operand lhs, m_lhs
load_operand rhs, m_rhs
coerce_to_doubles lhs, rhs, lhs_int, rhs_int, lhs_dbl, rhs_dbl, .both_int, .slow
fp_sub lhs_dbl, rhs_dbl
box_double_or_int32 dst, lhs_dbl
store_operand m_dst, dst
dispatch_next
.both_int:
sub32_overflow lhs_int, rhs_int, .overflow
box_int32_clean dst, lhs_int
store_operand m_dst, dst
dispatch_next
.overflow:
unbox_int32 lhs_int, lhs
unbox_int32 rhs_int, rhs
int_to_double lhs_dbl, lhs_int
int_to_double rhs_dbl, rhs_int
fp_sub lhs_dbl, rhs_dbl
fp_mov dst, lhs_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_sub
end
# Same pattern as Add but with multiplication.
# Extra complexity: 0 * negative = -0.0 (must produce negative zero double).
handler Mul
temp lhs, rhs, lhs_int, rhs_int, dst, sign_check
ftemp lhs_dbl, rhs_dbl
load_operand lhs, m_lhs
load_operand rhs, m_rhs
coerce_to_doubles lhs, rhs, lhs_int, rhs_int, lhs_dbl, rhs_dbl, .both_int, .slow
fp_mul lhs_dbl, rhs_dbl
box_double_or_int32 dst, lhs_dbl
store_operand m_dst, dst
dispatch_next
.both_int:
mul32_overflow lhs_int, rhs_int, .overflow
branch_nonzero lhs_int, .store_int
# Result is 0: check if either operand was negative -> -0.0
unbox_int32 sign_check, lhs
or sign_check, rhs_int
branch_negative sign_check, .negative_zero
.store_int:
box_int32_clean dst, lhs_int
store_operand m_dst, dst
dispatch_next
.negative_zero:
mov dst, NEGATIVE_ZERO
store_operand m_dst, dst
dispatch_next
.overflow:
unbox_int32 lhs_int, lhs
unbox_int32 rhs_int, rhs
int_to_double lhs_dbl, lhs_int
int_to_double rhs_dbl, rhs_int
fp_mul lhs_dbl, rhs_dbl
fp_mov dst, lhs_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_mul
end
# ============================================================================
# Control flow
# ============================================================================
handler Jump
temp target
load_label target, m_target
goto_handler target
end
# Conditional jumps: check boolean first (most common), then int32, then slow path.
# For JumpIf/JumpTrue/JumpFalse, a boolean's truth value is just bit 0.
# For int32, any nonzero low 32 bits means truthy.
handler JumpIf
temp condition, tag, truthy, target
load_operand condition, m_condition
extract_tag tag, condition
# Boolean fast path
branch_eq tag, BOOLEAN_TAG, .is_bool
# Int32 fast path
branch_eq tag, INT32_TAG, .is_int32
# Slow path: call helper to convert to boolean
call_helper asm_helper_to_boolean, condition, truthy
branch_nonzero truthy, .take_true
jmp .take_false
.is_bool:
branch_bits_set condition, 1, .take_true
jmp .take_false
.is_int32:
branch_nonzero32 condition, .take_true
jmp .take_false
.take_true:
load_label target, m_true_target
goto_handler target
.take_false:
load_label target, m_false_target
goto_handler target
end
handler JumpTrue
temp condition, tag, truthy, target
load_operand condition, m_condition
extract_tag tag, condition
branch_eq tag, BOOLEAN_TAG, .is_bool
branch_eq tag, INT32_TAG, .is_int32
call_helper asm_helper_to_boolean, condition, truthy
branch_nonzero truthy, .take
dispatch_next
.is_bool:
branch_bits_set condition, 1, .take
dispatch_next
.is_int32:
branch_nonzero32 condition, .take
dispatch_next
.take:
load_label target, m_target
goto_handler target
end
handler JumpFalse
temp condition, tag, truthy, target
load_operand condition, m_condition
extract_tag tag, condition
branch_eq tag, BOOLEAN_TAG, .is_bool
branch_eq tag, INT32_TAG, .is_int32
call_helper asm_helper_to_boolean, condition, truthy
branch_zero truthy, .take
dispatch_next
.is_bool:
branch_bits_clear condition, 1, .take
dispatch_next
.is_int32:
branch_zero32 condition, .take
dispatch_next
.take:
load_label target, m_target
goto_handler target
end
# Nullish check: undefined and null tags differ only in bit 0,
# so (tag & 0xFFFE) == UNDEFINED_TAG matches both.
handler JumpNullish
temp condition, tag, target
load_operand condition, m_condition
# Nullish: (tag & 0xFFFE) == 0x7FFE (matches undefined=0x7FFE and null=0x7FFF)
extract_tag tag, condition
and tag, 0xFFFE
branch_eq tag, UNDEFINED_TAG, .nullish
load_label target, m_false_target
goto_handler target
.nullish:
load_label target, m_true_target
goto_handler target
end
handler JumpUndefined
temp condition, undef, target
load_operand condition, m_condition
mov undef, UNDEFINED_SHIFTED
branch_eq condition, undef, .is_undefined
load_label target, m_false_target
goto_handler target
.is_undefined:
load_label target, m_true_target
goto_handler target
end
# Jump comparison handlers: use numeric_compare_coerce (handles mixed int32+double)
# combined with jump_binary_epilogue (provides .take_true, .take_false, .slow labels).
handler JumpLessThan
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare_coerce lhs, rhs, branch_lt_signed, branch_fp_less, .take_true, .take_false, .slow
jump_binary_epilogue asm_slow_path_jump_less_than
end
handler JumpGreaterThan
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare_coerce lhs, rhs, branch_gt_signed, branch_fp_greater, .take_true, .take_false, .slow
jump_binary_epilogue asm_slow_path_jump_greater_than
end
handler JumpLessThanEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare_coerce lhs, rhs, branch_le_signed, branch_fp_less_or_equal, .take_true, .take_false, .slow
jump_binary_epilogue asm_slow_path_jump_less_than_equals
end
handler JumpGreaterThanEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare_coerce lhs, rhs, branch_ge_signed, branch_fp_greater_or_equal, .take_true, .take_false, .slow
jump_binary_epilogue asm_slow_path_jump_greater_than_equals
end
handler JumpLooselyEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
loose_equality_core lhs, rhs, .take_true, .take_false, .slow
jump_binary_epilogue asm_slow_path_jump_loosely_equals
end
handler JumpLooselyInequals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
loose_equality_core lhs, rhs, .take_false, .take_true, .slow
jump_binary_epilogue asm_slow_path_jump_loosely_inequals
end
handler JumpStrictlyEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
strict_equality_core lhs, rhs, .take_true, .take_false, .slow
jump_binary_epilogue asm_slow_path_jump_strictly_equals
end
handler JumpStrictlyInequals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
strict_equality_core lhs, rhs, .take_false, .take_true, .slow
jump_binary_epilogue asm_slow_path_jump_strictly_inequals
end
# Fast path for ++x: int32 + 1 with overflow check.
# On overflow, convert to double and add 1.0.
handler Increment
temp value, tag, int_value, dst
ftemp result_dbl, one_dbl
load_operand value, m_dst
extract_tag tag, value
branch_ne tag, INT32_TAG, .slow
unbox_int32 int_value, value
add32_overflow int_value, 1, .overflow
box_int32_clean dst, int_value
store_operand m_dst, dst
dispatch_next
.overflow:
unbox_int32 int_value, value
int_to_double result_dbl, int_value
mov dst, DOUBLE_ONE
fp_mov one_dbl, dst
fp_add result_dbl, one_dbl
fp_mov dst, result_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_increment
end
# Fast path for --x: int32 - 1 with overflow check.
handler Decrement
temp value, tag, int_value, dst
ftemp result_dbl, one_dbl
load_operand value, m_dst
extract_tag tag, value
branch_ne tag, INT32_TAG, .slow
unbox_int32 int_value, value
sub32_overflow int_value, 1, .overflow
box_int32_clean dst, int_value
store_operand m_dst, dst
dispatch_next
.overflow:
unbox_int32 int_value, value
int_to_double result_dbl, int_value
mov dst, DOUBLE_ONE
fp_mov one_dbl, dst
fp_sub result_dbl, one_dbl
fp_mov dst, result_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_decrement
end
handler Not
temp value, tag, nullish_check, truthy, result
load_operand value, m_src
extract_tag tag, value
# Boolean fast path
branch_eq tag, BOOLEAN_TAG, .is_bool
# Int32 fast path
branch_eq tag, INT32_TAG, .is_int32
# Undefined/null -> !nullish = true
mov nullish_check, tag
and nullish_check, 0xFFFE
branch_eq nullish_check, UNDEFINED_TAG, .store_true
# Slow path for remaining types (object, string, etc)
# NB: Objects go through slow path to handle [[IsHTMLDDA]]
call_helper asm_helper_to_boolean, value, truthy
branch_zero truthy, .store_true
jmp .store_false
.is_bool:
branch_bits_clear value, 1, .store_true
jmp .store_false
.is_int32:
branch_zero32 value, .store_true
jmp .store_false
.store_true:
mov result, BOOLEAN_TRUE
store_operand m_dst, result
dispatch_next
.store_false:
mov result, BOOLEAN_FALSE
store_operand m_dst, result
dispatch_next
end
# ============================================================================
# Return / function call
# ============================================================================
handler Return
# Empty is the internal "no explicit value" marker. Returning it from
# bytecode means "return undefined" at the JS level.
temp value, empty_tag, caller_frame
load_operand value, m_value
mov empty_tag, EMPTY_TAG_SHIFTED
branch_ne value, empty_tag, .value_ready
mov value, UNDEFINED_SHIFTED
.value_ready:
# Inline JS-to-JS calls resume the caller directly from asm. Top-level
# returns instead exit back to the outer interpreter entry point.
load64 caller_frame, [exec_ctx, EXECUTION_CONTEXT_CALLER_FRAME]
branch_zero caller_frame, .top_level
pop_inline_frame_and_resume caller_frame, value
.top_level:
# Top-level return matches VM::run_executable(): write return_value,
# clear the exception slot, and leave the asm interpreter entirely.
# values[3] = return_value, values[1] = empty (clear exception)
store64 [values, 24], value
store64 [values, 8], empty_tag
exit
end
# Like Return, but does not clear the exception register (values[1]).
# Used at the end of a function body (after all user code).
handler End
# End shares the same inline-frame unwind logic as Return. The only
# top-level difference is that End preserves the current exception slot.
temp value, empty_tag, caller_frame
load_operand value, m_value
mov empty_tag, EMPTY_TAG_SHIFTED
branch_ne value, empty_tag, .value_ready
mov value, UNDEFINED_SHIFTED
.value_ready:
# Inline frame: resume the caller immediately.
load64 caller_frame, [exec_ctx, EXECUTION_CONTEXT_CALLER_FRAME]
branch_zero caller_frame, .top_level
pop_inline_frame_and_resume caller_frame, value
.top_level:
# Top-level end: publish the return value and exit without touching
# values[1], since End does not model a user-visible `return` opcode.
store64 [values, 24], value
exit
end
# Loads running_execution_context().lexical_environment into dst,
# NaN-boxed as a cell pointer.
handler GetLexicalEnvironment
temp env, tag
load64 env, [exec_ctx, EXECUTION_CONTEXT_LEXICAL_ENVIRONMENT]
mov tag, CELL_TAG_SHIFTED
or env, tag
store_operand m_dst, env
dispatch_next
end
handler SetLexicalEnvironment
call_slow_path asm_slow_path_set_lexical_environment
end
# ============================================================================
# Environment / binding access
# ============================================================================
# Inline environment chain walk + binding value load with TDZ check.
handler GetBinding
temp env, idx, binding, init, value
walk_env_chain m_cache, env, idx, .slow
load64 binding, [env, BINDINGS_DATA_PTR]
mul idx, idx, SIZEOF_BINDING
add binding, idx
# Check binding is initialized (TDZ)
load8 init, [binding, BINDING_INITIALIZED]
branch_zero init, .slow
load64 value, [binding, BINDING_VALUE]
store_operand m_dst, value
dispatch_next
.slow:
call_slow_path asm_slow_path_get_binding
end
# Inline environment chain walk + direct binding value load.
handler GetInitializedBinding
temp env, idx, binding, value
walk_env_chain m_cache, env, idx, .slow
load64 binding, [env, BINDINGS_DATA_PTR]
mul idx, idx, SIZEOF_BINDING
add binding, idx
load64 value, [binding, BINDING_VALUE]
store_operand m_dst, value
dispatch_next
.slow:
call_slow_path asm_slow_path_get_initialized_binding
end
# Inline environment chain walk + initialize binding (set value + initialized=true).
handler InitializeLexicalBinding
temp env, idx, binding, value, one
walk_env_chain m_cache, env, idx, .slow
load64 binding, [env, BINDINGS_DATA_PTR]
mul idx, idx, SIZEOF_BINDING
add binding, idx
load_operand value, m_src
store64 [binding, BINDING_VALUE], value
# Set initialized = true
mov one, 1
store8 [binding, BINDING_INITIALIZED], one
dispatch_next
.slow:
call_slow_path asm_slow_path_initialize_lexical_binding
end
# Inline environment chain walk + set mutable binding.
handler SetLexicalBinding
temp env, idx, binding, flag, value
walk_env_chain m_cache, env, idx, .slow
load64 binding, [env, BINDINGS_DATA_PTR]
mul idx, idx, SIZEOF_BINDING
add binding, idx
# Check initialized (TDZ)
load8 flag, [binding, BINDING_INITIALIZED]
branch_zero flag, .slow
# Check mutable
load8 flag, [binding, BINDING_MUTABLE]
branch_zero flag, .slow
load_operand value, m_src
store64 [binding, BINDING_VALUE], value
dispatch_next
.slow:
call_slow_path asm_slow_path_set_lexical_binding
end
# x++: save original to dst first, then increment src in-place.
handler PostfixIncrement
temp value, tag, int_value, dst
ftemp result_dbl, one_dbl
load_operand value, m_src
extract_tag tag, value
branch_ne tag, INT32_TAG, .slow
# Save original value to dst (the "postfix" part)
store_operand m_dst, value
# Increment in-place: src = src + 1
unbox_int32 int_value, value
add32_overflow int_value, 1, .overflow_after_store
box_int32_clean dst, int_value
store_operand m_src, dst
dispatch_next
.overflow_after_store:
unbox_int32 int_value, value
int_to_double result_dbl, int_value
mov dst, DOUBLE_ONE
fp_mov one_dbl, dst
fp_add result_dbl, one_dbl
fp_mov dst, result_dbl
store_operand m_src, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_postfix_increment
end
# Division result is stored as int32 when representable (e.g. 6/3 = 2),
# matching the Value(double) constructor's behavior. We don't use
# coerce_to_doubles here because we never need the both-int32 branch --
# both operands go straight to FP regs.
handler Div
temp lhs, rhs, tag, scratch_int, dst
ftemp lhs_dbl, rhs_dbl
load_operand lhs, m_lhs
load_operand rhs, m_rhs
extract_tag tag, lhs
branch_eq tag, INT32_TAG, .lhs_is_int32
# tag already has lhs tag
check_tag_is_double tag, .slow
fp_mov lhs_dbl, lhs
jmp .lhs_ok
.lhs_is_int32:
unbox_int32 scratch_int, lhs
int_to_double lhs_dbl, scratch_int
.lhs_ok:
extract_tag tag, rhs
branch_eq tag, INT32_TAG, .rhs_is_int32
# tag already has rhs tag
check_tag_is_double tag, .slow
fp_mov rhs_dbl, rhs
jmp .do_div
.rhs_is_int32:
unbox_int32 scratch_int, rhs
int_to_double rhs_dbl, scratch_int
.do_div:
fp_div lhs_dbl, rhs_dbl
# Try to store result as int32 if it's an integer in i32 range.
# NB: We can't use js_to_int32 here because fjcvtzs applies modular
# reduction (e.g. 2^33 -> 0) which is wrong -- we need a strict
# round-trip check: truncate to int32, convert back, compare.
double_to_int32 dst, lhs_dbl, .store_double
# Exclude negative zero: -0.0 truncates to 0 but must stay double.
branch_nonzero dst, .store_int
fp_mov dst, lhs_dbl
branch_negative dst, .store_double
.store_int:
box_int32 dst, dst
store_operand m_dst, dst
dispatch_next
.store_double:
canonicalize_nan dst, lhs_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_div
end
# Numeric comparison handlers: use numeric_compare macro for both-int32 and
# both-double fast paths, fall back to slow path for mixed/non-numeric types.
# The boolean_result_epilogue macro provides .store_true, .store_false, .slow labels.
handler LessThan
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare lhs, rhs, branch_lt_signed, branch_fp_less, .store_true, .store_false, .slow
boolean_result_epilogue asm_slow_path_less_than
end
handler LessThanEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare lhs, rhs, branch_le_signed, branch_fp_less_or_equal, .store_true, .store_false, .slow
boolean_result_epilogue asm_slow_path_less_than_equals
end
handler GreaterThan
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare lhs, rhs, branch_gt_signed, branch_fp_greater, .store_true, .store_false, .slow
boolean_result_epilogue asm_slow_path_greater_than
end
handler GreaterThanEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
numeric_compare lhs, rhs, branch_ge_signed, branch_fp_greater_or_equal, .store_true, .store_false, .slow
boolean_result_epilogue asm_slow_path_greater_than_equals
end
# Bitwise ops accept int32 and boolean, fall back to slow path for anything else.
handler BitwiseXor
bitwise_op xor, asm_slow_path_bitwise_xor
end
# ============================================================================
# Unary operators
# ============================================================================
# Fast path for numeric values: +x is a no-op for int32 and double.
handler UnaryPlus
temp value, tag
load_operand value, m_src
# Check if int32
extract_tag tag, value
branch_eq tag, INT32_TAG, .done
# tag already holds value's tag; check if double
check_tag_is_double tag, .slow
.done:
store_operand m_dst, value
dispatch_next
.slow:
call_slow_path asm_slow_path_unary_plus
end
# Check if value is TDZ (empty). If not, just continue.
handler ThrowIfTDZ
temp value, empty
load_operand value, m_src
mov empty, EMPTY_VALUE
branch_eq value, empty, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_throw_if_tdz
end
# Check if value is an object. Only throws on non-object (rare).
handler ThrowIfNotObject
temp value, tag
load_operand value, m_src
extract_tag tag, value
branch_ne tag, OBJECT_TAG, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_throw_if_not_object
end
# Check if value is nullish (undefined or null). Only throws on nullish (rare).
handler ThrowIfNullish
temp value, tag
load_operand value, m_src
extract_tag tag, value
and tag, 0xFFFE
branch_eq tag, UNDEFINED_TAG, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_throw_if_nullish
end
# Fast path for int32: ~value
handler BitwiseNot
temp value, tag, dst
load_operand value, m_src
extract_tag tag, value
branch_ne tag, INT32_TAG, .slow
# NOT the low 32 bits (not32 zeros upper 32), then re-box
mov dst, value
not32 dst
box_int32_clean dst, dst
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_bitwise_not
end
handler BitwiseAnd
bitwise_op and, asm_slow_path_bitwise_and
end
handler BitwiseOr
bitwise_op or, asm_slow_path_bitwise_or
end
# Shift ops: int32-only fast path, shift count masked to 0-31 per spec.
handler LeftShift
temp lhs, rhs, lhs_tag, rhs_tag, lhs_int, count, dst
load_operand lhs, m_lhs
load_operand rhs, m_rhs
extract_tag lhs_tag, lhs
branch_ne lhs_tag, INT32_TAG, .slow
extract_tag rhs_tag, rhs
branch_ne rhs_tag, INT32_TAG, .slow
unbox_int32 lhs_int, lhs
unbox_int32 count, rhs
and count, 31
shl lhs_int, count
box_int32 dst, lhs_int
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_left_shift
end
handler RightShift
temp lhs, rhs, lhs_tag, rhs_tag, lhs_int, count, dst
load_operand lhs, m_lhs
load_operand rhs, m_rhs
extract_tag lhs_tag, lhs
branch_ne lhs_tag, INT32_TAG, .slow
extract_tag rhs_tag, rhs
branch_ne rhs_tag, INT32_TAG, .slow
unbox_int32 lhs_int, lhs
unbox_int32 count, rhs
and count, 31
sar lhs_int, count
box_int32 dst, lhs_int
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_right_shift
end
# Unsigned right shift: result is always unsigned, so values > INT32_MAX
# must be stored as double (can't fit in a signed int32 NaN-box).
handler UnsignedRightShift
temp lhs, rhs, lhs_tag, rhs_tag, value, count, dst
ftemp dst_dbl
load_operand lhs, m_lhs
load_operand rhs, m_rhs
extract_tag lhs_tag, lhs
branch_ne lhs_tag, INT32_TAG, .slow
extract_tag rhs_tag, rhs
branch_ne rhs_tag, INT32_TAG, .slow
# u32 result = (u32)lhs >> (rhs % 32)
mov value, lhs
and value, 0xFFFFFFFF
unbox_int32 count, rhs
and count, 31
shr value, count
# If result > INT32_MAX, store as double
branch_bit_set value, 31, .as_double
box_int32_clean dst, value
store_operand m_dst, dst
dispatch_next
.as_double:
int_to_double dst_dbl, value
fp_mov dst, dst_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_unsigned_right_shift
end
# Modulo: int32-only fast path for non-negative dividend.
# Negative dividend falls to slow path to handle -0 and INT_MIN correctly.
handler Mod
temp lhs, rhs, lhs_tag, rhs_tag, lhs_int, rhs_int, quot, rem, dst
load_operand lhs, m_lhs
load_operand rhs, m_rhs
extract_tag lhs_tag, lhs
branch_ne lhs_tag, INT32_TAG, .slow
extract_tag rhs_tag, rhs
branch_ne rhs_tag, INT32_TAG, .slow
unbox_int32 lhs_int, lhs
unbox_int32 rhs_int, rhs
# Check d == 0
branch_zero rhs_int, .slow
# Check n >= 0 (positive fast path avoids INT_MIN/-1 and negative zero)
branch_negative lhs_int, .slow
divmod quot, rem, lhs_int, rhs_int
box_int32 dst, rem
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_mod
end
# ============================================================================
# Equality and comparison
# ============================================================================
# Equality handlers use the strict/loose_equality_core macros which handle
# type-specific comparisons (int32, boolean, undefined/null bitwise compare,
# double with NaN awareness, string pointer shortcut, bigint -> slow path).
handler StrictlyEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
strict_equality_core lhs, rhs, .store_true, .store_false, .slow
boolean_result_epilogue asm_slow_path_strictly_equals
end
handler StrictlyInequals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
strict_equality_core lhs, rhs, .store_false, .store_true, .slow
boolean_result_epilogue asm_slow_path_strictly_inequals
end
# Inline environment chain walk + get callee and this.
handler GetCalleeAndThisFromEnvironment
temp env, idx, binding, init, value
walk_env_chain m_cache, env, idx, .slow
load64 binding, [env, BINDINGS_DATA_PTR]
mul idx, idx, SIZEOF_BINDING
add binding, idx
# TDZ state lives in Binding.initialized; the value slot itself starts as
# undefined, so checking for EMPTY would miss cached second-hit calls.
load8 init, [binding, BINDING_INITIALIZED]
branch_zero init, .slow
load64 value, [binding, BINDING_VALUE]
store_operand m_callee, value
# this = undefined (DeclarativeEnvironment.with_base_object() always returns nullptr)
mov value, UNDEFINED_SHIFTED
store_operand m_this_value, value
dispatch_next
.slow:
call_slow_path asm_slow_path_get_callee_and_this
end
handler LooselyEquals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
loose_equality_core lhs, rhs, .store_true, .store_false, .slow
boolean_result_epilogue asm_slow_path_loosely_equals
end
handler LooselyInequals
temp lhs, rhs
load_operand lhs, m_lhs
load_operand rhs, m_rhs
loose_equality_core lhs, rhs, .store_false, .store_true, .slow
boolean_result_epilogue asm_slow_path_loosely_inequals
end
handler UnaryMinus
temp value, tag, int_value, dst
ftemp dst_dbl
load_operand value, m_src
extract_tag tag, value
branch_ne tag, INT32_TAG, .try_double
unbox_int32 int_value, value
# -0 check: if value is 0, result is -0.0 (double)
branch_zero int_value, .negative_zero
# 32-bit negate with overflow detection (INT32_MIN)
neg32_overflow int_value, .overflow
box_int32_clean dst, int_value
store_operand m_dst, dst
dispatch_next
.negative_zero:
mov dst, NEGATIVE_ZERO
store_operand m_dst, dst
dispatch_next
.overflow:
# INT32_MIN: -(-2147483648) = 2147483648.0
int_to_double dst_dbl, int_value
fp_mov dst, dst_dbl
store_operand m_dst, dst
dispatch_next
.try_double:
# tag already has the lhs tag
check_tag_is_double tag, .slow
# Negate double: flip sign bit (bit 63)
toggle_bit value, 63
store_operand m_dst, value
dispatch_next
.slow:
call_slow_path asm_slow_path_unary_minus
end
# x--: save original to dst first, then decrement src in-place.
handler PostfixDecrement
temp value, tag, int_value, dst
ftemp result_dbl, one_dbl
load_operand value, m_src
extract_tag tag, value
branch_ne tag, INT32_TAG, .slow
# Save original value to dst (the "postfix" part)
store_operand m_dst, value
# Decrement in-place: src = src - 1
unbox_int32 int_value, value
sub32_overflow int_value, 1, .overflow_after_store
box_int32_clean dst, int_value
store_operand m_src, dst
dispatch_next
.overflow_after_store:
unbox_int32 int_value, value
int_to_double result_dbl, int_value
mov dst, DOUBLE_ONE
fp_mov one_dbl, dst
fp_sub result_dbl, one_dbl
fp_mov dst, result_dbl
store_operand m_src, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_postfix_decrement
end
handler ToInt32
temp value, tag, tag_copy, dst
ftemp value_dbl
load_operand value, m_value
extract_tag tag, value
branch_ne tag, INT32_TAG, .try_double
# Already int32, just copy
store_operand m_dst, value
dispatch_next
.try_double:
# `tag` already has the value's tag; check if double (copy first because
# check_tag_is_double clobbers its argument and `tag` is needed again
# at .try_boolean for the boolean check).
mov tag_copy, tag
check_tag_is_double tag_copy, .try_boolean
# Convert double to int32 using JS ToInt32 semantics.
# With FEAT_JSCVT: fjcvtzs handles everything in one instruction.
# Without: truncate + round-trip check, slow path on mismatch.
fp_mov value_dbl, value
js_to_int32 dst, value_dbl, .slow
box_int32_clean dst, dst
store_operand m_dst, dst
dispatch_next
.try_boolean:
branch_ne tag, BOOLEAN_TAG, .slow
# Convert boolean to int32: false -> 0, true -> 1
and value, 1
box_int32_clean dst, value
store_operand m_dst, dst
dispatch_next
.slow:
# Slow path handles other types (string, object, nullish, etc) and uncommon cases.
call_slow_path asm_slow_path_to_int32
end
# ============================================================================
# Property access (indexed + named + inline caches)
# ============================================================================
# Fast path for array[int32_index] = value with Packed/Holey indexed storage.
handler PutByValue
temp kind, base, prop, base_tag, prop_tag, index, obj, flags, storage_kind, size, elements, src, capacity_addr, capacity, slot, empty_tag, kind_byte, addr, src_int32, max, result
ftemp src_dbl
# Only fast-path Normal puts (not Getter/Setter/Own)
load8 kind, [pb, pc, m_kind]
branch_ne kind, PUT_KIND_NORMAL, .slow
load_operand base, m_base
load_operand prop, m_property
extract_tag base_tag, base
branch_ne base_tag, OBJECT_TAG, .slow
# Check property is non-negative int32
extract_tag prop_tag, prop
branch_ne prop_tag, INT32_TAG, .slow
mov index, prop
and index, 0xFFFFFFFF
branch_bit_set index, 31, .slow
unbox_object obj, base
# Check IsTypedArray flag -- branch to typed-array path early.
load8 flags, [obj, OBJECT_FLAGS]
branch_bits_set flags, OBJECT_FLAG_IS_TYPED_ARRAY, .try_typed_array
# Check !may_interfere_with_indexed_property_access
branch_bits_set flags, OBJECT_FLAG_MAY_INTERFERE, .slow
# Packed is the hot path: existing elements can be overwritten directly.
load8 storage_kind, [obj, OBJECT_INDEXED_STORAGE_KIND]
branch_ne storage_kind, INDEXED_STORAGE_KIND_PACKED, .not_packed
load32 size, [obj, OBJECT_INDEXED_ARRAY_LIKE_SIZE]
branch_ge_unsigned index, size, .slow
load64 elements, [obj, OBJECT_INDEXED_ELEMENTS]
load_operand src, m_src
store64 [elements, index, 8], src
dispatch_next
.not_packed:
branch_ne storage_kind, INDEXED_STORAGE_KIND_HOLEY, .slow
# Holey arrays need a slot load to distinguish existing elements from holes.
load32 size, [obj, OBJECT_INDEXED_ARRAY_LIKE_SIZE]
branch_ge_unsigned index, size, .slow
load64 elements, [obj, OBJECT_INDEXED_ELEMENTS]
branch_zero elements, .try_holey_array_slow
mov capacity_addr, elements
sub capacity_addr, 8
load32 capacity, [capacity_addr, 0]
branch_ge_unsigned index, capacity, .try_holey_array_slow
load64 slot, [elements, index, 8]
mov empty_tag, EMPTY_TAG_SHIFTED
branch_eq slot, empty_tag, .try_holey_array_slow
load_operand src, m_src
store64 [elements, index, 8], src
dispatch_next
.try_holey_array_slow:
call_interp asm_try_put_by_value_holey_array, result
branch_nonzero result, .slow
dispatch_next
.try_typed_array:
# Load cached data pointer (pre-computed: buffer.data() + byte_offset)
# nullptr means uncached -> C++ helper will resolve the access.
load64 elements, [obj, TYPED_ARRAY_CACHED_DATA_PTR]
branch_zero elements, .try_typed_array_slow
# Cached pointers only exist for fixed-length typed arrays, so array_length
# is known to hold a concrete u32 value here.
load32 capacity, [obj, TYPED_ARRAY_ARRAY_LENGTH_VALUE]
branch_ge_unsigned index, capacity, .slow
load8 kind_byte, [obj, TYPED_ARRAY_KIND]
load_operand src, m_src
extract_tag base_tag, src
branch_eq base_tag, INT32_TAG, .ta_store_int32
# Non-int32 value: only handle float typed arrays with double sources.
branch_eq kind_byte, TYPED_ARRAY_KIND_FLOAT32, .ta_store_float32
branch_ne kind_byte, TYPED_ARRAY_KIND_FLOAT64, .try_typed_array_slow
# Compute store address before check_is_double mangles its argument.
mov addr, index
shl addr, 3
add addr, elements
check_is_double src, .try_typed_array_slow
store64 [addr, 0], src
dispatch_next
.ta_store_float32:
mov addr, index
shl addr, 2
add addr, elements
check_is_double src, .try_typed_array_slow
fp_mov src_dbl, src
double_to_float src_dbl, src_dbl
storef32 [addr, 0], src_dbl
dispatch_next
.ta_store_int32:
unbox_int32 src_int32, src
branch_any_eq kind_byte, TYPED_ARRAY_KIND_INT32, TYPED_ARRAY_KIND_UINT32, .ta_put_int32
branch_eq kind_byte, TYPED_ARRAY_KIND_FLOAT32, .ta_put_float32
branch_eq kind_byte, TYPED_ARRAY_KIND_UINT8_CLAMPED, .ta_put_uint8_clamped
branch_any_eq kind_byte, TYPED_ARRAY_KIND_UINT8, TYPED_ARRAY_KIND_INT8, .ta_put_uint8
branch_any_eq kind_byte, TYPED_ARRAY_KIND_UINT16, TYPED_ARRAY_KIND_INT16, .ta_put_uint16
jmp .try_typed_array_slow
.ta_put_int32:
store32 [elements, index, 4], src_int32
dispatch_next
.ta_put_float32:
int_to_double src_dbl, src_int32
double_to_float src_dbl, src_dbl
mov addr, index
shl addr, 2
add addr, elements
storef32 [addr, 0], src_dbl
dispatch_next
.ta_put_uint8_clamped:
branch_negative src_int32, .ta_put_uint8_clamped_zero
mov max, 255
branch_ge_unsigned src_int32, max, .ta_put_uint8_clamped_max
store8 [elements, index], src_int32
dispatch_next
.ta_put_uint8_clamped_zero:
mov src_int32, 0
store8 [elements, index], src_int32
dispatch_next
.ta_put_uint8_clamped_max:
mov src_int32, 255
store8 [elements, index], src_int32
dispatch_next
.ta_put_uint8:
store8 [elements, index], src_int32
dispatch_next
.ta_put_uint16:
mov addr, index
add addr, index
add addr, elements
store16 [addr, 0], src_int32
dispatch_next
.try_typed_array_slow:
call_interp asm_try_put_by_value_typed_array, result
branch_nonzero result, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_put_by_value
end
# Inline cache fast path for property access (own + prototype chain).
handler GetById
temp base, tag, obj, shape, plc, cache_shape, cache_proto, prop_offset, dict_gen, cur_dict_gen, props, value, result
load_operand base, m_base
extract_tag tag, base
branch_ne tag, OBJECT_TAG, .try_cache
unbox_object obj, base
load64 shape, [obj, OBJECT_SHAPE]
# Get PropertyLookupCache* (direct pointer from instruction stream)
load64 plc, [pb, pc, m_cache]
load_pair64 cache_shape, cache_proto, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_SHAPE], [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROTOTYPE]
branch_ne cache_shape, shape, .try_cache
branch_nonzero cache_proto, .proto
# Check dictionary generation matches
load_pair32 prop_offset, dict_gen, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROPERTY_OFFSET], [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_DICTIONARY_GENERATION]
load32 cur_dict_gen, [shape, SHAPE_DICTIONARY_GENERATION]
branch_ne dict_gen, cur_dict_gen, .try_cache
# IC hit! Load property value via get_direct (own property)
load64 props, [obj, OBJECT_NAMED_PROPERTIES]
load64 value, [props, prop_offset, 8]
# Check value is not an accessor
extract_tag tag, value
branch_eq tag, ACCESSOR_TAG, .try_cache
store_operand m_dst, value
dispatch_next
.proto:
# cache_proto = prototype Object*, shape = object's shape, plc = PLC base
load64 prop_offset, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROTOTYPE_CHAIN_VALIDITY]
branch_zero prop_offset, .try_cache
load8 tag, [prop_offset, PROTOTYPE_CHAIN_VALIDITY_VALID]
branch_zero tag, .try_cache
load_pair32 prop_offset, dict_gen, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROPERTY_OFFSET], [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_DICTIONARY_GENERATION]
load32 cur_dict_gen, [shape, SHAPE_DICTIONARY_GENERATION]
branch_ne dict_gen, cur_dict_gen, .try_cache
load64 props, [cache_proto, OBJECT_NAMED_PROPERTIES]
load64 value, [props, prop_offset, 8]
extract_tag tag, value
branch_eq tag, ACCESSOR_TAG, .try_cache
store_operand m_dst, value
dispatch_next
.try_cache:
# Try all cache entries via C++ helper
call_interp asm_try_get_by_id_cache, result
branch_zero result, .done
.slow:
call_slow_path asm_slow_path_get_by_id
.done:
dispatch_next
end
# Inline cache fast path for own-property store (ChangeOwnProperty).
handler PutById
temp base, tag, obj, shape, plc, cache_shape, cache_proto, prop_offset, dict_gen, cur_dict_gen, props, value, src, result
load_operand base, m_base
extract_tag tag, base
branch_ne tag, OBJECT_TAG, .try_cache
unbox_object obj, base
load64 shape, [obj, OBJECT_SHAPE]
load64 plc, [pb, pc, m_cache]
load_pair64 cache_shape, cache_proto, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_SHAPE], [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROTOTYPE]
branch_ne cache_shape, shape, .try_cache
branch_nonzero cache_proto, .try_cache
load_pair32 prop_offset, dict_gen, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROPERTY_OFFSET], [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_DICTIONARY_GENERATION]
load32 cur_dict_gen, [shape, SHAPE_DICTIONARY_GENERATION]
branch_ne dict_gen, cur_dict_gen, .try_cache
# Check current value at prop_offset is not an accessor
load64 props, [obj, OBJECT_NAMED_PROPERTIES]
load64 value, [props, prop_offset, 8]
extract_tag tag, value
branch_eq tag, ACCESSOR_TAG, .try_cache
# IC hit! Store new value via put_direct.
load_operand src, m_src
store64 [props, prop_offset, 8], src
dispatch_next
.try_cache:
# Try all cache entries via C++ helper (handles AddOwnProperty)
call_interp asm_try_put_by_id_cache, result
branch_zero result, .done
.slow:
call_slow_path asm_slow_path_put_by_id
.done:
dispatch_next
end
# Fast path for array[int32_index] with Packed/Holey indexed storage.
handler GetByValue
temp base, prop, base_tag, prop_tag, index, obj, flags, storage_kind, size, elements, slot, capacity_addr, capacity, kind_byte, raw, addr, neg_zero, dst, result
ftemp slot_dbl
load_operand base, m_base
load_operand prop, m_property
extract_tag base_tag, base
branch_ne base_tag, OBJECT_TAG, .slow
extract_tag prop_tag, prop
branch_ne prop_tag, INT32_TAG, .slow
mov index, prop
and index, 0xFFFFFFFF
branch_bit_set index, 31, .slow
unbox_object obj, base
load8 flags, [obj, OBJECT_FLAGS]
branch_bits_set flags, OBJECT_FLAG_IS_TYPED_ARRAY, .try_typed_array
branch_bits_set flags, OBJECT_FLAG_MAY_INTERFERE, .slow
# Packed is the hot path: in-bounds elements are always present.
load8 storage_kind, [obj, OBJECT_INDEXED_STORAGE_KIND]
branch_ne storage_kind, INDEXED_STORAGE_KIND_PACKED, .not_packed
load32 size, [obj, OBJECT_INDEXED_ARRAY_LIKE_SIZE]
branch_ge_unsigned index, size, .slow
load64 elements, [obj, OBJECT_INDEXED_ELEMENTS]
load64 dst, [elements, index, 8]
# NB: No accessor check needed -- Packed/Holey storage
# can only hold default-attributed data properties.
store_operand m_dst, dst
dispatch_next
.not_packed:
branch_ne storage_kind, INDEXED_STORAGE_KIND_HOLEY, .slow
# Holey arrays need a slot load to distinguish present elements from holes.
load32 size, [obj, OBJECT_INDEXED_ARRAY_LIKE_SIZE]
branch_ge_unsigned index, size, .slow
load64 elements, [obj, OBJECT_INDEXED_ELEMENTS]
branch_zero elements, .slow
mov capacity_addr, elements
sub capacity_addr, 8
load32 capacity, [capacity_addr, 0]
branch_ge_unsigned index, capacity, .slow
load64 slot, [elements, index, 8]
mov neg_zero, EMPTY_TAG_SHIFTED
branch_eq slot, neg_zero, .slow
store_operand m_dst, slot
dispatch_next
.try_typed_array:
load64 elements, [obj, TYPED_ARRAY_CACHED_DATA_PTR]
branch_zero elements, .try_typed_array_slow
# Cached pointers only exist for fixed-length typed arrays, so array_length
# is known to hold a concrete u32 value here.
load32 capacity, [obj, TYPED_ARRAY_ARRAY_LENGTH_VALUE]
branch_ge_unsigned index, capacity, .try_typed_array_slow
load8 kind_byte, [obj, TYPED_ARRAY_KIND]
branch_eq kind_byte, TYPED_ARRAY_KIND_INT32, .ta_int32
branch_any_eq kind_byte, TYPED_ARRAY_KIND_UINT8, TYPED_ARRAY_KIND_UINT8_CLAMPED, .ta_uint8
branch_eq kind_byte, TYPED_ARRAY_KIND_UINT16, .ta_uint16
branch_eq kind_byte, TYPED_ARRAY_KIND_INT8, .ta_int8
branch_eq kind_byte, TYPED_ARRAY_KIND_INT16, .ta_int16
branch_eq kind_byte, TYPED_ARRAY_KIND_UINT32, .ta_uint32
branch_eq kind_byte, TYPED_ARRAY_KIND_FLOAT32, .ta_float32
branch_eq kind_byte, TYPED_ARRAY_KIND_FLOAT64, .ta_float64
jmp .try_typed_array_slow
.ta_int32:
load32 raw, [elements, index, 4]
jmp .ta_box_int32
.ta_uint8:
load8 raw, [elements, index]
jmp .ta_box_int32
.ta_uint16:
mov addr, index
add addr, index
load16 raw, [elements, addr]
jmp .ta_box_int32
.ta_int8:
load8s raw, [elements, index]
jmp .ta_box_int32
.ta_int16:
mov addr, index
add addr, index
load16s raw, [elements, addr]
jmp .ta_box_int32
.ta_float32:
mov addr, index
shl addr, 2
add addr, elements
loadf32 slot_dbl, [addr, 0]
float_to_double slot_dbl, slot_dbl
fp_mov slot, slot_dbl
mov neg_zero, NEGATIVE_ZERO
branch_eq slot, neg_zero, .ta_f64_as_double
double_to_int32 raw, slot_dbl, .ta_f64_as_double
branch_nonzero raw, .ta_f64_as_int
jmp .ta_f64_as_int
.ta_float64:
mov addr, index
shl addr, 3
add addr, elements
load64 slot, [addr, 0]
fp_mov slot_dbl, slot
# Exclude negative zero early (slot gets clobbered by double_to_int32).
mov neg_zero, NEGATIVE_ZERO
branch_eq slot, neg_zero, .ta_f64_as_double
double_to_int32 raw, slot_dbl, .ta_f64_as_double
branch_nonzero raw, .ta_f64_as_int
# double_to_int32 succeeded with 0 -- this is +0.0, box as int
.ta_f64_as_int:
box_int32 dst, raw
store_operand m_dst, dst
dispatch_next
.ta_f64_as_double:
canonicalize_nan dst, slot_dbl
store_operand m_dst, dst
dispatch_next
.ta_uint32:
load32 raw, [elements, index, 4]
branch_bit_set raw, 31, .ta_uint32_to_double
jmp .ta_box_int32
.ta_uint32_to_double:
int_to_double slot_dbl, raw
fp_mov dst, slot_dbl
store_operand m_dst, dst
dispatch_next
.ta_box_int32:
box_int32_clean dst, raw
store_operand m_dst, dst
dispatch_next
.try_typed_array_slow:
call_interp asm_try_get_by_value_typed_array, result
branch_nonzero result, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_get_by_value
end
# Fast path for Array.length (magical length property).
# Also includes IC fast path for non-array objects (same as GetById).
handler GetLength
temp base, tag, obj, flags, shape, plc, cache_shape, cache_proto, prop_offset, dict_gen, cur_dict_gen, props, value, length, sign_check, dst
ftemp length_dbl
load_operand base, m_base
extract_tag tag, base
branch_ne tag, OBJECT_TAG, .slow
unbox_object obj, base
load8 flags, [obj, OBJECT_FLAGS]
branch_bits_set flags, OBJECT_FLAG_HAS_MAGICAL_LENGTH, .magical_length
# Non-magical length: IC fast path (same as GetById)
load64 shape, [obj, OBJECT_SHAPE]
load64 plc, [pb, pc, m_cache]
load_pair64 cache_shape, cache_proto, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_SHAPE], [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROTOTYPE]
branch_ne cache_shape, shape, .slow
branch_nonzero cache_proto, .slow
load_pair32 prop_offset, dict_gen, [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROPERTY_OFFSET], [plc, PROPERTY_LOOKUP_CACHE_ENTRY0_DICTIONARY_GENERATION]
load32 cur_dict_gen, [shape, SHAPE_DICTIONARY_GENERATION]
branch_ne dict_gen, cur_dict_gen, .slow
load64 props, [obj, OBJECT_NAMED_PROPERTIES]
load64 value, [props, prop_offset, 8]
extract_tag tag, value
branch_eq tag, ACCESSOR_TAG, .slow
store_operand m_dst, value
dispatch_next
.magical_length:
# Object.m_indexed_array_like_size (u32). Box as int32 when bit 31 is
# clear; otherwise widen to a double so the value isn't reinterpreted
# as a negative int32.
load32 length, [obj, OBJECT_INDEXED_ARRAY_LIKE_SIZE]
mov sign_check, length
shr sign_check, 31
branch_nonzero sign_check, .length_double
box_int32 dst, length
store_operand m_dst, dst
dispatch_next
.length_double:
int_to_double length_dbl, length
fp_mov dst, length_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_get_length
end
# Inline cache fast path for global variable access via the global object.
handler GetGlobal
temp realm, global_object, env, gvc, cache_serial, env_serial, shape, cache_shape, cur_dict_gen, prop_offset, dict_gen, props, value, tag, has_env, in_module, idx, binding, init, result
load64 realm, [exec_ctx, EXECUTION_CONTEXT_REALM]
load_pair64 global_object, env, [realm, REALM_GLOBAL_OBJECT], [realm, REALM_GLOBAL_DECLARATIVE_ENVIRONMENT]
load64 gvc, [pb, pc, m_cache]
load64 cache_serial, [gvc, GLOBAL_VARIABLE_CACHE_ENVIRONMENT_SERIAL]
load64 env_serial, [env, DECLARATIVE_ENVIRONMENT_SERIAL]
branch_ne cache_serial, env_serial, .slow
# Shape-based fast path: check entries[0].shape matches global_object.shape
# (falls through to env binding path on shape mismatch)
load64 shape, [global_object, OBJECT_SHAPE]
load64 cache_shape, [gvc, PROPERTY_LOOKUP_CACHE_ENTRY0_SHAPE]
branch_ne cache_shape, shape, .try_env_binding
load32 cur_dict_gen, [shape, SHAPE_DICTIONARY_GENERATION]
load_pair32 prop_offset, dict_gen, [gvc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROPERTY_OFFSET], [gvc, PROPERTY_LOOKUP_CACHE_ENTRY0_DICTIONARY_GENERATION]
branch_ne dict_gen, cur_dict_gen, .try_env_binding
# IC hit! Load property value via get_direct
load64 props, [global_object, OBJECT_NAMED_PROPERTIES]
load64 value, [props, prop_offset, 8]
extract_tag tag, value
branch_eq tag, ACCESSOR_TAG, .slow
store_operand m_dst, value
dispatch_next
.try_env_binding:
load8 has_env, [gvc, GLOBAL_VARIABLE_CACHE_HAS_ENVIRONMENT_BINDING]
branch_zero has_env, .slow
# Bail to C++ for module environments (rare).
load8 in_module, [gvc, GLOBAL_VARIABLE_CACHE_IN_MODULE_ENVIRONMENT]
branch_nonzero in_module, .slow_env
# Inline env binding: index into global_declarative_environment bindings.
load32 idx, [gvc, GLOBAL_VARIABLE_CACHE_ENVIRONMENT_BINDING_INDEX]
load64 binding, [env, BINDINGS_DATA_PTR]
mul idx, idx, SIZEOF_BINDING
add binding, idx
load8 init, [binding, BINDING_INITIALIZED]
branch_zero init, .slow
load64 value, [binding, BINDING_VALUE]
store_operand m_dst, value
dispatch_next
.slow_env:
call_interp asm_try_get_global_env_binding, result
branch_nonzero result, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_get_global
end
# Inline cache fast path for global variable store via the global object.
handler SetGlobal
temp realm, global_object, env, gvc, cache_serial, env_serial, shape, cache_shape, cur_dict_gen, prop_offset, dict_gen, props, value, tag, has_env, in_module, idx, binding, flag, src, result
load64 realm, [exec_ctx, EXECUTION_CONTEXT_REALM]
load_pair64 global_object, env, [realm, REALM_GLOBAL_OBJECT], [realm, REALM_GLOBAL_DECLARATIVE_ENVIRONMENT]
load64 gvc, [pb, pc, m_cache]
load64 cache_serial, [gvc, GLOBAL_VARIABLE_CACHE_ENVIRONMENT_SERIAL]
load64 env_serial, [env, DECLARATIVE_ENVIRONMENT_SERIAL]
branch_ne cache_serial, env_serial, .slow
load64 shape, [global_object, OBJECT_SHAPE]
load64 cache_shape, [gvc, PROPERTY_LOOKUP_CACHE_ENTRY0_SHAPE]
branch_ne cache_shape, shape, .try_env_binding
load32 cur_dict_gen, [shape, SHAPE_DICTIONARY_GENERATION]
load_pair32 prop_offset, dict_gen, [gvc, PROPERTY_LOOKUP_CACHE_ENTRY0_PROPERTY_OFFSET], [gvc, PROPERTY_LOOKUP_CACHE_ENTRY0_DICTIONARY_GENERATION]
branch_ne dict_gen, cur_dict_gen, .try_env_binding
# IC hit! Load current value to check it's not an accessor.
load64 props, [global_object, OBJECT_NAMED_PROPERTIES]
load64 value, [props, prop_offset, 8]
extract_tag tag, value
branch_eq tag, ACCESSOR_TAG, .slow
load_operand src, m_src
store64 [props, prop_offset, 8], src
dispatch_next
.try_env_binding:
load8 has_env, [gvc, GLOBAL_VARIABLE_CACHE_HAS_ENVIRONMENT_BINDING]
branch_zero has_env, .slow
load8 in_module, [gvc, GLOBAL_VARIABLE_CACHE_IN_MODULE_ENVIRONMENT]
branch_nonzero in_module, .slow_env
load32 idx, [gvc, GLOBAL_VARIABLE_CACHE_ENVIRONMENT_BINDING_INDEX]
load64 binding, [env, BINDINGS_DATA_PTR]
mul idx, idx, SIZEOF_BINDING
add binding, idx
load8 flag, [binding, BINDING_INITIALIZED]
branch_zero flag, .slow
load8 flag, [binding, BINDING_MUTABLE]
branch_zero flag, .slow
load_operand src, m_src
store64 [binding, BINDING_VALUE], src
dispatch_next
.slow_env:
call_interp asm_try_set_global_env_binding, result
branch_nonzero result, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_set_global
end
handler Call
# Inline Call in asm for the two callee kinds that can stay in the
# dispatch loop without taking the full Call slow path:
#
# - ECMAScriptFunctionObject with inline-ready bytecode: build the
# callee frame here and dispatch at pc = 0 of the callee bytecode.
# Cases that need function-environment allocation or sloppy primitive
# this-boxing can't stay in pure asm but also don't want the full
# slow path (which would insert a run_executable() boundary and an
# observable microtask drain), so they detour through the
# asm_try_inline_call helper at .call_interp_inline.
#
# - RawNativeFunction: build a callee ExecutionContext here, call the
# stored C++ function pointer directly via call_raw_native, and then
# tear the frame down on return. Exceptions go through a dedicated
# helper that unwinds the callee frame before dispatching to a JS
# handler (see .call_raw_native_exception).
#
# Everything else -- non-functions, NativeJavaScriptBackedFunction,
# ECMAScript functions that can't inline, Proxies, ... -- falls through
# to .call_slow, i.e. asm_slow_path_call.
#
# High-level flow of the ECMAScript fast path:
# 1. Validate the callee and load its shared function metadata.
# 2. Bind `this` inline when we can do so without allocations.
# 3. Reserve an InterpreterStack frame and populate ExecutionContext.
# 4. Materialize [registers | locals | constants | arguments].
# 5. Swap VM state over to the callee frame and dispatch at pc = 0.
temp callee, callee_value, flags, shared_data, exec_ptr, meta, this_value, tag, scratch, formal_count, passed_count, arg_count, total_slots, regs_locals_count, frame_bytes, vm_ptr, stack_limit, frame_base, value_tail, realm, lex_env, priv_env, empty_tag, som_src, som_lo, som_hi, return_pc, return_dst, base_pc, slot_offset, slot_end, const_count, const_data, const_idx, const_value, write_idx, arg_idx, arg_ops, arg_value, undef_slot, fill_end, native_func, variant, native_return, helper_arg, native_pc, exception_pc, native_total_bytes, after_pc, dst_offset, after_offset, result
load_operand callee_value, m_callee
extract_tag tag, callee_value
branch_ne tag, OBJECT_TAG, .call_slow
unbox_object callee, callee_value
# Non-functions still go through the normal Call slow path for proper
# error reporting. Non-ECMAScript function objects get a
# RawNativeFunction fast path attempt before we fully give up.
load8 flags, [callee, OBJECT_FLAGS]
branch_bits_clear flags, OBJECT_FLAG_IS_FUNCTION, .call_slow
branch_bits_clear flags, OBJECT_FLAG_IS_ECMASCRIPT_FUNCTION_OBJECT, .call_try_native
load64 shared_data, [callee, ECMASCRIPT_FUNCTION_OBJECT_SHARED_DATA]
load_pair64 exec_ptr, meta, [shared_data, SHARED_FUNCTION_INSTANCE_DATA_EXECUTABLE], [shared_data, SHARED_FUNCTION_INSTANCE_DATA_ASM_CALL_METADATA]
branch_bits_clear meta, SHARED_FUNCTION_INSTANCE_DATA_ASM_CALL_METADATA_CAN_INLINE_CALL, .call_slow
# NewFunctionEnvironment() allocates and has to stay out of the pure asm
# path, but we still preserve inline-call semantics via .call_interp_inline.
branch_bits_set meta, SHARED_FUNCTION_INSTANCE_DATA_ASM_CALL_METADATA_FUNCTION_ENVIRONMENT_NEEDED, .call_interp_inline
# Bind this without allocations. Sloppy primitive this-values still need
# ToObject(), so they use the C++ inline-frame helper.
#
# this_value starts as "empty" to match the normal interpreter behavior
# for callees that never observe `this`.
mov this_value, EMPTY_TAG_SHIFTED
branch_bits_clear meta, SHARED_FUNCTION_INSTANCE_DATA_ASM_CALL_METADATA_USES_THIS, .this_ready
load_operand this_value, m_this_value
branch_bits_set meta, SHARED_FUNCTION_INSTANCE_DATA_ASM_CALL_METADATA_STRICT, .this_ready
# Sloppy null/undefined binds the callee realm's global object.
# Sloppy primitive receivers need ToObject(), which may allocate
# wrappers, so they go through the helper instead of the full slow path.
extract_tag tag, this_value
mov scratch, tag
and scratch, 0xFFFE
branch_eq scratch, UNDEFINED_TAG, .sloppy_global_this
branch_eq tag, OBJECT_TAG, .this_ready
jmp .call_interp_inline
.sloppy_global_this:
load64 scratch, [callee, OBJECT_SHAPE]
load64 scratch, [scratch, SHAPE_REALM]
load64 scratch, [scratch, REALM_GLOBAL_ENVIRONMENT]
load64 scratch, [scratch, GLOBAL_ENVIRONMENT_GLOBAL_THIS_VALUE]
# Match Value(Object*): keep only the low 48 pointer bits before boxing.
shl scratch, 16
shr scratch, 16
mov this_value, OBJECT_TAG_SHIFTED
or this_value, scratch
.this_ready:
# The low 32 bits of the packed metadata word hold the formal parameter count.
and meta, 0xFFFFFFFF
load32 passed_count, [pb, pc, m_argument_count]
mov formal_count, meta
branch_ge_unsigned formal_count, passed_count, .arg_count_ready
mov formal_count, passed_count
.arg_count_ready:
load_pair32 regs_locals_count, total_slots, [exec_ptr, EXECUTABLE_REGISTERS_AND_LOCALS_COUNT], [exec_ptr, EXECUTABLE_REGISTERS_AND_LOCALS_AND_CONSTANTS_COUNT]
# Inline InterpreterStack::allocate().
add total_slots, formal_count
mov frame_bytes, total_slots
shl frame_bytes, 3
add frame_bytes, SIZEOF_EXECUTION_CONTEXT
load_vm vm_ptr
lea vm_ptr, [vm_ptr, VM_INTERPRETER_STACK]
load_pair64 frame_base, stack_limit, [vm_ptr, INTERPRETER_STACK_TOP], [vm_ptr, INTERPRETER_STACK_LIMIT]
add frame_bytes, frame_base
branch_ge_unsigned stack_limit, frame_bytes, .stack_ok
jmp .call_slow
.stack_ok:
load_vm vm_ptr
store64 [vm_ptr, VM_INTERPRETER_STACK_TOP], frame_bytes
# Set up the callee ExecutionContext header exactly the way
# VM::push_inline_frame() / run_executable() would see it.
lea value_tail, [frame_base, SIZEOF_EXECUTION_CONTEXT]
store_pair32 [frame_base, EXECUTION_CONTEXT_REGISTERS_AND_CONSTANTS_AND_LOCALS_AND_ARGUMENTS_COUNT], [frame_base, EXECUTION_CONTEXT_ARGUMENT_COUNT], total_slots, formal_count
load32 scratch, [pb, pc, m_argument_count]
store32 [frame_base, EXECUTION_CONTEXT_PASSED_ARGUMENT_COUNT], scratch
load64 realm, [callee, OBJECT_SHAPE]
load64 realm, [realm, SHAPE_REALM]
store_pair64 [frame_base, EXECUTION_CONTEXT_FUNCTION], [frame_base, EXECUTION_CONTEXT_REALM], callee, realm
load_pair64 lex_env, priv_env, [callee, ECMASCRIPT_FUNCTION_OBJECT_ENVIRONMENT], [callee, ECMASCRIPT_FUNCTION_OBJECT_PRIVATE_ENVIRONMENT]
store_pair64 [frame_base, EXECUTION_CONTEXT_LEXICAL_ENVIRONMENT], [frame_base, EXECUTION_CONTEXT_VARIABLE_ENVIRONMENT], lex_env, lex_env
store64 [frame_base, EXECUTION_CONTEXT_PRIVATE_ENVIRONMENT], priv_env
store_pair64 [frame_base, EXECUTION_CONTEXT_THIS_VALUE], [frame_base, EXECUTION_CONTEXT_EXECUTABLE], this_value, exec_ptr
mov empty_tag, EMPTY_TAG_SHIFTED
store_pair64 [value_tail, ACCUMULATOR_REG_OFFSET], [value_tail, EXCEPTION_REG_OFFSET], empty_tag, empty_tag
store64 [value_tail, THIS_VALUE_REG_OFFSET], this_value
store_pair64 [value_tail, RETURN_VALUE_REG_OFFSET], [value_tail, SAVED_LEXICAL_ENVIRONMENT_REG_OFFSET], empty_tag, empty_tag
# ScriptOrModule is a two-word Variant in ExecutionContext, so copy both
# machine words explicitly.
lea scratch, [frame_base, EXECUTION_CONTEXT_SCRIPT_OR_MODULE]
lea som_src, [callee, ECMASCRIPT_FUNCTION_OBJECT_SCRIPT_OR_MODULE]
load_pair64 som_lo, som_hi, [som_src, 0], [som_src, 8]
store64 [scratch, 0], som_lo
store64 [scratch, 8], som_hi
store32 [frame_base, EXECUTION_CONTEXT_PROGRAM_COUNTER], 0
store32 [frame_base, EXECUTION_CONTEXT_SKIP_WHEN_DETERMINING_INCUMBENT_COUNTER], 0
mov scratch, EXECUTION_CONTEXT_NO_YIELD_CONTINUATION
store32 [frame_base, EXECUTION_CONTEXT_YIELD_CONTINUATION], scratch
store8 [frame_base, EXECUTION_CONTEXT_YIELD_IS_AWAIT], 0
store8 [frame_base, EXECUTION_CONTEXT_CALLER_IS_CONSTRUCT], 0
store64 [frame_base, EXECUTION_CONTEXT_CALLER_FRAME], exec_ctx
load_pair32 return_pc, return_dst, [pb, pc, m_length], [pb, pc, m_dst]
lea base_pc, [pb, pc]
sub base_pc, pb
add return_pc, base_pc
store_pair32 [frame_base, EXECUTION_CONTEXT_CALLER_RETURN_PC], [frame_base, EXECUTION_CONTEXT_CALLER_DST_RAW], return_pc, return_dst
# values = [registers | locals | constants | arguments]
# Walk value_tail with two cursors: slot_offset for the byte index and
# write_idx for the element index when copying constants/arguments.
mov slot_end, regs_locals_count
shl slot_end, 3
mov slot_offset, RESERVED_REGISTERS_SIZE
.clear_registers_and_locals:
mov scratch, slot_offset
add scratch, 8
branch_ge_unsigned scratch, slot_end, .clear_registers_and_locals_tail
store_pair64 [value_tail, slot_offset, 0], [value_tail, slot_offset, 8], empty_tag, empty_tag
add slot_offset, 16
jmp .clear_registers_and_locals
.clear_registers_and_locals_tail:
branch_ge_unsigned slot_offset, slot_end, .copy_constants
store64 [value_tail, slot_offset], empty_tag
.copy_constants:
load64 const_data, [frame_base, EXECUTION_CONTEXT_EXECUTABLE]
load_pair64 const_count, const_data, [const_data, EXECUTABLE_ASM_CONSTANTS_SIZE], [const_data, EXECUTABLE_ASM_CONSTANTS_DATA]
mov write_idx, regs_locals_count
xor const_idx, const_idx
.copy_constants_loop:
branch_ge_unsigned const_idx, const_count, .copy_arguments
load64 const_value, [const_data, const_idx, 8]
store64 [value_tail, write_idx, 8], const_value
add const_idx, 1
add write_idx, 1
jmp .copy_constants_loop
.copy_arguments:
load32 arg_count, [pb, pc, m_argument_count]
mov write_idx, regs_locals_count
add write_idx, const_count
lea scratch, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
lea arg_ops, [pb, pc]
add arg_ops, m_expression_string
add arg_ops, 4
xor arg_idx, arg_idx
.copy_arguments_loop:
# The operand array in the bytecode stores caller register indices.
branch_ge_unsigned arg_idx, arg_count, .fill_missing_arguments
load32 arg_value, [arg_ops, arg_idx, 4]
load64 arg_value, [scratch, arg_value, 8]
store64 [value_tail, write_idx, 8], arg_value
add arg_idx, 1
add write_idx, 1
jmp .copy_arguments_loop
.fill_missing_arguments:
mov fill_end, write_idx
add fill_end, formal_count
sub fill_end, arg_count
mov undef_slot, UNDEFINED_SHIFTED
.fill_missing_arguments_loop:
branch_ge_unsigned write_idx, fill_end, .enter_callee
store64 [value_tail, write_idx, 8], undef_slot
add write_idx, 1
jmp .fill_missing_arguments_loop
.enter_callee:
load64 pb, [frame_base, EXECUTION_CONTEXT_EXECUTABLE]
load64 pb, [pb, EXECUTABLE_BYTECODE_DATA]
load_vm vm_ptr
store64 [vm_ptr, VM_RUNNING_EXECUTION_CONTEXT], frame_base
mov exec_ctx, frame_base
lea values, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
xor pc, pc
goto_handler pc
.call_interp_inline:
# Shared escape hatch for the cases that need C++ help to build the
# inline frame correctly but must not take the full Call slow path,
# since that would insert a run_executable() boundary and observable
# microtask drain.
call_interp asm_try_inline_call, result
branch_nonzero result, .call_slow
load_vm vm_ptr
load64 exec_ctx, [vm_ptr, VM_RUNNING_EXECUTION_CONTEXT]
lea values, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
load64 scratch, [exec_ctx, EXECUTION_CONTEXT_EXECUTABLE]
load64 pb, [scratch, EXECUTABLE_BYTECODE_DATA]
xor pc, pc
goto_handler pc
.call_try_native:
# Fast path for RawNativeFunction: the callee is a plain C++ function
# pointer with no JS-visible prologue, so we can build the callee frame
# ourselves and jump straight at the entry point. NativeFunction
# objects that still carry a callback (NativeJavaScriptBackedFunction)
# do not have this flag set and fall through to .call_slow.
load8 flags, [callee, OBJECT_FLAGS]
branch_bits_clear flags, OBJECT_FLAG_IS_RAW_NATIVE_FUNCTION, .call_slow
# Unlike the ECMAScript path we don't pad to the formal parameter count:
# native functions read their arguments via the passed-count API, so we
# only need space for the call-site arguments plus the EC header.
load32 arg_count, [pb, pc, m_argument_count]
mov native_total_bytes, arg_count
shl native_total_bytes, 3
add native_total_bytes, SIZEOF_EXECUTION_CONTEXT
# Inline InterpreterStack::allocate(): bail to C++ if the interpreter
# stack doesn't have room for the new frame.
load_vm vm_ptr
lea vm_ptr, [vm_ptr, VM_INTERPRETER_STACK]
load_pair64 frame_base, stack_limit, [vm_ptr, INTERPRETER_STACK_TOP], [vm_ptr, INTERPRETER_STACK_LIMIT]
add native_total_bytes, frame_base
branch_ge_unsigned stack_limit, native_total_bytes, .native_interpreter_stack_ok
jmp .call_slow
.native_interpreter_stack_ok:
# RawNativeFunctions run real C++ code on the host stack, so we also
# have to check that we're not about to blow past the VM's reserved
# stack limit. The ECMAScript path can skip this because it never
# leaves asm.
load_vm vm_ptr
lea vm_ptr, [vm_ptr, VM_STACK_INFO]
load64 stack_limit, [vm_ptr, STACK_INFO_BASE]
add stack_limit, VM_STACK_SPACE_LIMIT
branch_ge_unsigned fp, stack_limit, .native_stack_space_ok
jmp .call_slow
.native_stack_space_ok:
# Commit the new interpreter stack top.
load_vm vm_ptr
store64 [vm_ptr, VM_INTERPRETER_STACK_TOP], native_total_bytes
# Populate the callee EC to match VM::push_execution_context plus
# NativeFunction::internal_call. value_tail walks past the EC header to
# the argument Value array.
lea value_tail, [frame_base, SIZEOF_EXECUTION_CONTEXT]
# For natives, argument_count and "registers+..." total are both just
# the call-site argument count: there are no registers, locals, or
# constants.
store_pair32 [frame_base, EXECUTION_CONTEXT_REGISTERS_AND_CONSTANTS_AND_LOCALS_AND_ARGUMENTS_COUNT], [frame_base, EXECUTION_CONTEXT_ARGUMENT_COUNT], arg_count, arg_count
store32 [frame_base, EXECUTION_CONTEXT_PASSED_ARGUMENT_COUNT], arg_count
# Shape stores a Realm pointer; use it as the callee EC realm.
load64 realm, [callee, OBJECT_SHAPE]
load64 realm, [realm, SHAPE_REALM]
store_pair64 [frame_base, EXECUTION_CONTEXT_FUNCTION], [frame_base, EXECUTION_CONTEXT_REALM], callee, realm
# Mirror NativeFunction::internal_call: a raw native has no environment
# of its own, so lexical/variable/private environments are copied
# straight from the caller frame.
load_pair64 lex_env, scratch, [exec_ctx, EXECUTION_CONTEXT_LEXICAL_ENVIRONMENT], [exec_ctx, EXECUTION_CONTEXT_VARIABLE_ENVIRONMENT]
store_pair64 [frame_base, EXECUTION_CONTEXT_LEXICAL_ENVIRONMENT], [frame_base, EXECUTION_CONTEXT_VARIABLE_ENVIRONMENT], lex_env, scratch
load64 priv_env, [exec_ctx, EXECUTION_CONTEXT_PRIVATE_ENVIRONMENT]
store64 [frame_base, EXECUTION_CONTEXT_PRIVATE_ENVIRONMENT], priv_env
# |this| is forwarded unchanged. Native builtins do their own type
# checks on the receiver where they need to.
load_operand this_value, m_this_value
store64 [frame_base, EXECUTION_CONTEXT_THIS_VALUE], this_value
# Zero out the ScriptOrModule variant (two words) and Executable
# pointer. Native frames don't belong to any script/module.
xor scratch, scratch
lea som_src, [frame_base, EXECUTION_CONTEXT_SCRIPT_OR_MODULE]
store_pair64 [som_src, 0], [som_src, 8], scratch, scratch
store64 [frame_base, EXECUTION_CONTEXT_EXECUTABLE], scratch
store32 [frame_base, EXECUTION_CONTEXT_PROGRAM_COUNTER], 0
store32 [frame_base, EXECUTION_CONTEXT_SKIP_WHEN_DETERMINING_INCUMBENT_COUNTER], 0
mov scratch, EXECUTION_CONTEXT_NO_YIELD_CONTINUATION
store32 [frame_base, EXECUTION_CONTEXT_YIELD_CONTINUATION], scratch
store8 [frame_base, EXECUTION_CONTEXT_YIELD_IS_AWAIT], 0
store8 [frame_base, EXECUTION_CONTEXT_CALLER_IS_CONSTRUCT], 0
# While asm runs, the authoritative program counter lives in the `pc`
# register and the caller EC's stored program_counter is stale. Before
# we leave asm to run native C++ that may throw, sync `pc` into the
# caller EC as a bytecode offset (pc - pb). The exception helper and
# VM::handle_exception both read from the caller EC after unwind.
lea native_pc, [pb, pc]
sub native_pc, pb
store32 [exec_ctx, EXECUTION_CONTEXT_PROGRAM_COUNTER], native_pc
store64 [frame_base, EXECUTION_CONTEXT_CALLER_FRAME], exec_ctx
# CALLER_RETURN_PC is the bytecode offset of the instruction after
# the Call. CALLER_DST_RAW records where the return value should
# be written in the caller's value array.
load32 after_pc, [pb, pc, m_length]
add after_pc, native_pc
store32 [frame_base, EXECUTION_CONTEXT_CALLER_RETURN_PC], after_pc
load32 dst_offset, [pb, pc, m_dst]
store32 [frame_base, EXECUTION_CONTEXT_CALLER_DST_RAW], dst_offset
# Copy the call-site arguments from the caller's value array into the
# callee frame's argument tail. scratch points at the caller's value
# array, arg_ops at the Operand[] that trails the fixed Call instruction
# fields. The Call layout ends with `m_expression_string:
# Optional<StringTableIndex>` (4 bytes via the sentinel specialization)
# followed by `m_arguments`, so base + offsetof(m_expression_string) + 4
# is the operand array.
lea scratch, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
lea arg_ops, [pb, pc]
add arg_ops, m_expression_string
add arg_ops, 4
xor arg_idx, arg_idx
.copy_native_arguments_loop:
branch_ge_unsigned arg_idx, arg_count, .enter_raw_native
load32 arg_value, [arg_ops, arg_idx, 4]
load64 arg_value, [scratch, arg_value, 8]
store64 [value_tail, arg_idx, 8], arg_value
add arg_idx, 1
jmp .copy_native_arguments_loop
.enter_raw_native:
# Swap the running ExecutionContext over to the callee and point the
# asm `values` register at its argument array. After this, we look like
# a normal inline frame from the VM's perspective.
load_vm vm_ptr
store64 [vm_ptr, VM_RUNNING_EXECUTION_CONTEXT], frame_base
mov exec_ctx, frame_base
lea values, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
# Invoke the raw C++ function pointer. call_raw_native lowers to a
# native call through the platform ABI and surfaces the returned
# ThrowCompletionOr<Value> via (payload, variant). The variant low byte
# is 0 for a Value, 1 for an ErrorValue; anything else means the native
# threw and payload is the thrown Value, not a return value.
load64 native_func, [callee, RAW_NATIVE_FUNCTION_NATIVE_FUNCTION]
call_raw_native native_func, native_return, variant
and variant, 0xFF
branch_nonzero variant, .call_raw_native_exception
# Normal return path: tear the callee frame off the interpreter stack,
# restore the caller as the running ExecutionContext, write the return
# value into the caller's m_dst operand, and dispatch the next insn.
load64 frame_base, [exec_ctx, EXECUTION_CONTEXT_CALLER_FRAME]
load_vm vm_ptr
store64 [vm_ptr, VM_RUNNING_EXECUTION_CONTEXT], frame_base
store64 [vm_ptr, VM_INTERPRETER_STACK_TOP], exec_ctx
mov exec_ctx, frame_base
lea values, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
store_operand m_dst, native_return
load32 after_offset, [pb, pc, m_length]
dispatch_variable after_offset
.call_raw_native_exception:
# The native threw. Hand the thrown Value off to a C++ helper, which
# unwinds the callee frame off the interpreter stack and calls through
# to VM::handle_exception. Return value follows the standard asm
# slow-path convention (see AsmInterpreter.cpp:127):
# >= 0 : an enclosing handler was found; the result is the new
# program counter to resume at inside the (post-unwind)
# running execution context.
# < 0 : no handler; bail out of the asm dispatch loop entirely.
# native_return is pinned to rax by call_raw_native; helper_arg is
# pinned to rcx by call_helper, so this mov is the explicit bridge
# between the two ABIs.
mov helper_arg, native_return
call_helper asm_helper_handle_raw_native_exception, helper_arg, exception_pc
branch_negative exception_pc, .call_exit_asm
# Reload exec_ctx/values/pb/pc from the caller frame the helper left
# us on, and resume dispatching at its program_counter (which the
# helper already updated to the handler entry).
load_vm vm_ptr
load64 exec_ctx, [vm_ptr, VM_RUNNING_EXECUTION_CONTEXT]
lea values, [exec_ctx, SIZEOF_EXECUTION_CONTEXT]
load64 scratch, [exec_ctx, EXECUTION_CONTEXT_EXECUTABLE]
load64 pb, [scratch, EXECUTABLE_BYTECODE_DATA]
load32 native_pc, [exec_ctx, EXECUTION_CONTEXT_PROGRAM_COUNTER]
mov pc, native_pc
goto_handler pc
.call_exit_asm:
# No JS handler caught the native exception; bail out of the asm
# dispatch loop and let the C++ caller of run_asm() see the throw.
exit
.call_slow:
call_slow_path asm_slow_path_call
end
# Fast paths for common Math builtins with a single double argument.
# Before using the fast path, we validate that the callee is still the
# original builtin function (user code may have reassigned e.g. Math.abs).
handler CallBuiltinMathAbs
temp arg, tag, int_value, dst
ftemp arg_dbl
validate_callee_builtin BUILTIN_MATH_ABS, .slow
load_operand arg, m_argument
check_is_double arg, .try_abs_int32
# abs(double) = clear sign bit (bit 63)
clear_bit arg, 63
store_operand m_dst, arg
dispatch_next
.try_abs_int32:
extract_tag tag, arg
branch_ne tag, INT32_TAG, .slow
# abs(int32): negate if negative
unbox_int32 int_value, arg
branch_not_negative int_value, .abs_positive
neg32_overflow int_value, .abs_overflow
.abs_positive:
box_int32_clean dst, int_value
store_operand m_dst, dst
dispatch_next
.abs_overflow:
# INT32_MIN: abs(-2147483648) = 2147483648.0
unbox_int32 int_value, arg
neg int_value
int_to_double arg_dbl, int_value
fp_mov dst, arg_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_math_abs
end
handler CallBuiltinMathFloor
temp arg, dst
ftemp arg_dbl
validate_callee_builtin BUILTIN_MATH_FLOOR, .slow
load_operand arg, m_argument
check_is_double arg, .slow
fp_mov arg_dbl, arg
fp_floor arg_dbl, arg_dbl
box_double_or_int32 dst, arg_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_math_floor
end
handler CallBuiltinMathCeil
temp arg, dst
ftemp arg_dbl
validate_callee_builtin BUILTIN_MATH_CEIL, .slow
load_operand arg, m_argument
check_is_double arg, .slow
fp_mov arg_dbl, arg
fp_ceil arg_dbl, arg_dbl
box_double_or_int32 dst, arg_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_math_ceil
end
handler CallBuiltinMathSqrt
temp arg, dst
ftemp arg_dbl
validate_callee_builtin BUILTIN_MATH_SQRT, .slow
load_operand arg, m_argument
check_is_double arg, .slow
fp_mov arg_dbl, arg
fp_sqrt arg_dbl, arg_dbl
box_double_or_int32 dst, arg_dbl
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_math_sqrt
end
handler CallBuiltinMathExp
temp arg, result
ftemp arg_dbl
validate_callee_builtin BUILTIN_MATH_EXP, .slow
load_operand arg, m_argument
check_is_double arg, .slow
fp_mov arg_dbl, arg
call_helper asm_helper_math_exp, arg, result
store_operand m_dst, result
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_math_exp
end
handler CallBuiltinMathLog
call_slow_path asm_slow_path_call_builtin_math_log
end
handler CallBuiltinMathPow
call_slow_path asm_slow_path_call_builtin_math_pow
end
handler CallBuiltinMathImul
call_slow_path asm_slow_path_call_builtin_math_imul
end
handler CallBuiltinMathRandom
call_slow_path asm_slow_path_call_builtin_math_random
end
handler CallBuiltinMathRound
call_slow_path asm_slow_path_call_builtin_math_round
end
handler CallBuiltinMathSin
call_slow_path asm_slow_path_call_builtin_math_sin
end
handler CallBuiltinMathCos
call_slow_path asm_slow_path_call_builtin_math_cos
end
handler CallBuiltinMathTan
call_slow_path asm_slow_path_call_builtin_math_tan
end
handler CallBuiltinRegExpPrototypeExec
call_slow_path asm_slow_path_call_builtin_regexp_prototype_exec
end
handler CallBuiltinRegExpPrototypeReplace
call_slow_path asm_slow_path_call_builtin_regexp_prototype_replace
end
handler CallBuiltinRegExpPrototypeSplit
call_slow_path asm_slow_path_call_builtin_regexp_prototype_split
end
handler CallBuiltinOrdinaryHasInstance
call_slow_path asm_slow_path_call_builtin_ordinary_has_instance
end
handler CallBuiltinArrayIteratorPrototypeNext
call_slow_path asm_slow_path_call_builtin_array_iterator_prototype_next
end
handler CallBuiltinMapIteratorPrototypeNext
call_slow_path asm_slow_path_call_builtin_map_iterator_prototype_next
end
handler CallBuiltinSetIteratorPrototypeNext
call_slow_path asm_slow_path_call_builtin_set_iterator_prototype_next
end
handler CallBuiltinStringIteratorPrototypeNext
call_slow_path asm_slow_path_call_builtin_string_iterator_prototype_next
end
handler CallBuiltinStringFromCharCode
temp arg, tag, code_unit, result
validate_callee_builtin BUILTIN_STRING_FROM_CHAR_CODE, .slow
load_operand arg, m_argument
extract_tag tag, arg
branch_ne tag, INT32_TAG, .slow
unbox_int32 code_unit, arg
and code_unit, 0xffff
branch_ge_unsigned code_unit, 0x80, .single_code_unit
call_helper asm_helper_single_ascii_character_string, code_unit, result
store_operand m_dst, result
dispatch_next
.single_code_unit:
call_helper asm_helper_single_utf16_code_unit_string, code_unit, result
store_operand m_dst, result
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_string_from_char_code
end
handler CallBuiltinStringPrototypeCharCodeAt
temp this_value, tag, string, arg, index, code_unit, dst
validate_callee_builtin BUILTIN_STRING_PROTOTYPE_CHAR_CODE_AT, .slow
load_operand this_value, m_this_value
extract_tag tag, this_value
branch_ne tag, STRING_TAG, .slow
unbox_object string, this_value
load_operand arg, m_argument
extract_tag tag, arg
branch_ne tag, INT32_TAG, .slow
unbox_int32 index, arg
branch_negative index, .out_of_bounds
load_primitive_string_utf16_code_unit string, index, code_unit, .out_of_bounds, .slow
box_int32_clean dst, code_unit
store_operand m_dst, dst
dispatch_next
.out_of_bounds:
mov dst, CANON_NAN_BITS
store_operand m_dst, dst
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_string_prototype_char_code_at
end
handler CallBuiltinStringPrototypeCharAt
temp this_value, tag, string, arg, index, code_unit, zero, result
validate_callee_builtin BUILTIN_STRING_PROTOTYPE_CHAR_AT, .slow
load_operand this_value, m_this_value
extract_tag tag, this_value
branch_ne tag, STRING_TAG, .slow
unbox_object string, this_value
load_operand arg, m_argument
extract_tag tag, arg
branch_ne tag, INT32_TAG, .slow
unbox_int32 index, arg
branch_negative index, .empty
load_primitive_string_utf16_code_unit string, index, code_unit, .empty, .slow
branch_ge_unsigned code_unit, 0x80, .slow
call_helper asm_helper_single_ascii_character_string, code_unit, result
store_operand m_dst, result
dispatch_next
.empty:
mov zero, 0
call_helper asm_helper_empty_string, zero, result
store_operand m_dst, result
dispatch_next
.slow:
call_slow_path asm_slow_path_call_builtin_string_prototype_char_at
end
# ============================================================================
# Slow-path-only handlers
# ============================================================================
# Handlers below are pure slow-path delegations: no fast path is worthwhile
# because the operation is inherently complex (object allocation, prototype
# chain walks, etc). Having them here avoids the generic fallback handler's
# overhead of saving/restoring all temporaries.
handler GetObjectPropertyIterator
call_slow_path asm_slow_path_get_object_property_iterator
end
handler ObjectPropertyIteratorNext
temp it_value, tag, iterator, fast_path, expected, cache, cached_shape, receiver, current_shape, is_dict, cur_dict_gen, dict_gen, storage_kind, packed_kind, size, expected_size, validity, valid, indexed_count, next_indexed, key, key_index, named_index, named_size, named_data, exhausted, packed_kind_byte, slow_kind, scratch
load_operand it_value, m_iterator_object
extract_tag tag, it_value
branch_ne tag, OBJECT_TAG, .slow
unbox_object iterator, it_value
load8 fast_path, [iterator, PROPERTY_NAME_ITERATOR_FAST_PATH]
mov expected, OBJECT_PROPERTY_ITERATOR_FAST_PATH_NONE
branch_eq fast_path, expected, .slow
# These guards mirror PropertyNameIterator::fast_path_still_valid(). If
# the receiver or prototype chain no longer matches the cached snapshot,
# we drop to C++ and continue in deoptimized mode for the rest of the
# enumeration.
load_pair64 cache, cached_shape, [iterator, PROPERTY_NAME_ITERATOR_PROPERTY_CACHE], [iterator, PROPERTY_NAME_ITERATOR_SHAPE]
load64 receiver, [iterator, PROPERTY_NAME_ITERATOR_OBJECT]
load64 current_shape, [receiver, OBJECT_SHAPE]
branch_ne current_shape, cached_shape, .slow
load8 is_dict, [iterator, PROPERTY_NAME_ITERATOR_SHAPE_IS_DICTIONARY]
branch_zero is_dict, .check_receiver
load32 cur_dict_gen, [current_shape, SHAPE_DICTIONARY_GENERATION]
load32 dict_gen, [iterator, PROPERTY_NAME_ITERATOR_SHAPE_DICTIONARY_GENERATION]
branch_ne cur_dict_gen, dict_gen, .slow
.check_receiver:
mov packed_kind_byte, OBJECT_PROPERTY_ITERATOR_FAST_PATH_PACKED_INDEXED
branch_ne fast_path, packed_kind_byte, .check_proto
load8 storage_kind, [receiver, OBJECT_INDEXED_STORAGE_KIND]
mov packed_kind, INDEXED_STORAGE_KIND_PACKED
branch_ne storage_kind, packed_kind, .slow
load32 size, [receiver, OBJECT_INDEXED_ARRAY_LIKE_SIZE]
load32 expected_size, [iterator, PROPERTY_NAME_ITERATOR_INDEXED_PROPERTY_COUNT]
branch_ne size, expected_size, .slow
.check_proto:
load64 validity, [iterator, PROPERTY_NAME_ITERATOR_PROTOTYPE_CHAIN_VALIDITY]
branch_zero validity, .next_key
load8 valid, [validity, PROTOTYPE_CHAIN_VALIDITY_VALID]
branch_zero valid, .slow
.next_key:
# property_values is laid out as:
# [receiver packed index keys..., flattened named keys...]
load_pair32 indexed_count, next_indexed, [iterator, PROPERTY_NAME_ITERATOR_INDEXED_PROPERTY_COUNT], [iterator, PROPERTY_NAME_ITERATOR_NEXT_INDEXED_PROPERTY]
branch_ge_unsigned next_indexed, indexed_count, .named
load64 key, [cache, OBJECT_PROPERTY_ITERATOR_CACHE_DATA_PROPERTY_VALUES_DATA]
load64 key, [key, next_indexed, 8]
add next_indexed, 1
store32 [iterator, PROPERTY_NAME_ITERATOR_NEXT_INDEXED_PROPERTY], next_indexed
store_operand m_dst_value, key
mov scratch, BOOLEAN_FALSE
store_operand m_dst_done, scratch
dispatch_next
.named:
load64 named_index, [iterator, PROPERTY_NAME_ITERATOR_NEXT_PROPERTY]
load64 named_size, [cache, OBJECT_PROPERTY_ITERATOR_CACHE_DATA_PROPERTY_VALUES_SIZE]
sub named_size, indexed_count
branch_ge_unsigned named_index, named_size, .done
mov key_index, named_index
add key_index, indexed_count
load64 named_data, [cache, OBJECT_PROPERTY_ITERATOR_CACHE_DATA_PROPERTY_VALUES_DATA]
load64 key, [named_data, key_index, 8]
add named_index, 1
store64 [iterator, PROPERTY_NAME_ITERATOR_NEXT_PROPERTY], named_index
store_operand m_dst_value, key
mov scratch, BOOLEAN_FALSE
store_operand m_dst_done, scratch
dispatch_next
.done:
load64 exhausted, [iterator, PROPERTY_NAME_ITERATOR_ITERATOR_CACHE_SLOT]
branch_zero exhausted, .store_done
# Return the exhausted iterator object to the bytecode-site cache so the
# next execution of this loop can reset and reuse it.
mov scratch, 0
store64 [iterator, PROPERTY_NAME_ITERATOR_OBJECT], scratch
store64 [exhausted, OBJECT_PROPERTY_ITERATOR_CACHE_REUSABLE_PROPERTY_NAME_ITERATOR], iterator
store64 [iterator, PROPERTY_NAME_ITERATOR_ITERATOR_CACHE_SLOT], scratch
.store_done:
mov scratch, BOOLEAN_TRUE
store_operand m_dst_done, scratch
dispatch_next
.slow:
call_slow_path asm_slow_path_object_property_iterator_next
end
handler CallConstruct
call_slow_path asm_slow_path_call_construct
end
handler NewObject
call_slow_path asm_slow_path_new_object
end
handler CacheObjectShape
call_slow_path asm_slow_path_cache_object_shape
end
handler InitObjectLiteralProperty
call_slow_path asm_slow_path_init_object_literal_property
end
handler NewArray
call_slow_path asm_slow_path_new_array
end
handler InstanceOf
call_slow_path asm_slow_path_instance_of
end
# Fast path: if this_value register is already cached (non-empty), skip the slow path.
handler ResolveThisBinding
temp this_value, empty
load64 this_value, [values, THIS_VALUE_REG_OFFSET]
mov empty, EMPTY_VALUE
branch_eq this_value, empty, .slow
dispatch_next
.slow:
call_slow_path asm_slow_path_resolve_this_binding
end
handler GetPrivateById
call_slow_path asm_slow_path_get_private_by_id
end
handler PutPrivateById
call_slow_path asm_slow_path_put_private_by_id
end