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LibJS: Remove derivable fields from ExecutionContext

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Remove four fields that are trivially derivable from other fields
already present in the ExecutionContext:

- global_object (from realm)
- global_declarative_environment (from realm)
- identifier_table (from executable)
- property_key_table (from executable)

This shrinks ExecutionContext from 192 to 160 bytes (-17%).

The asmint's GetGlobal/SetGlobal handlers now load through the realm
pointer, taking advantage of the cached declarative environment
pointer added in the previous commit.
This commit is contained in:
Andreas Kling
2026-03-08 11:34:32 +01:00
committed by Andreas Kling
parent e70f580e5c
commit 96d02d5249
Notes: github-actions[bot] 2026-03-11 12:35:42 +00:00 
Author: https://github.com/awesomekling
Commit: https://github.com/LadybirdBrowser/ladybird/commit/96d02d5249d
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/8360
Reviewed-by: https://github.com/shannonbooth
6 changed files with 24 additions and 28 deletions
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14
Libraries/LibJS/Bytecode/AsmInterpreter/asmint.asm
View File

@@ -1717,9 +1717,10 @@ end
# Inline cache fast path for global variable access via the global object.
handler GetGlobal
# Load global_declarative_environment and global_object
load64 t1, [exec_ctx, EXECUTION_CONTEXT_GLOBAL_DECLARATIVE_ENVIRONMENT]
load64 t2, [exec_ctx, EXECUTION_CONTEXT_GLOBAL_OBJECT]
# Load global_declarative_environment and global_object via realm
load64 t0, [exec_ctx, EXECUTION_CONTEXT_REALM]
load64 t2, [t0, REALM_GLOBAL_OBJECT]
load64 t1, [t0, REALM_GLOBAL_DECLARATIVE_ENVIRONMENT]
# Get GlobalVariableCache* (direct pointer from instruction stream)
load64 t3, [pb, pc, m_cache]
# Check environment_serial_number matches
@@ -1774,9 +1775,10 @@ end
# Inline cache fast path for global variable store via the global object.
handler SetGlobal
# Load global_declarative_environment and global_object
load64 t1, [exec_ctx, EXECUTION_CONTEXT_GLOBAL_DECLARATIVE_ENVIRONMENT]
load64 t2, [exec_ctx, EXECUTION_CONTEXT_GLOBAL_OBJECT]
# Load global_declarative_environment and global_object via realm
load64 t0, [exec_ctx, EXECUTION_CONTEXT_REALM]
load64 t2, [t0, REALM_GLOBAL_OBJECT]
load64 t1, [t0, REALM_GLOBAL_DECLARATIVE_ENVIRONMENT]
# Get GlobalVariableCache* (direct pointer from instruction stream)
load64 t3, [pb, pc, m_cache]
# Check environment_serial_number matches

9
Libraries/LibJS/Bytecode/AsmInterpreter/gen_asm_offsets.cpp
View File

@@ -17,6 +17,7 @@
#include <LibJS/Runtime/FunctionObject.h>
#include <LibJS/Runtime/IndexedProperties.h>
#include <LibJS/Runtime/Object.h>
#include <LibJS/Runtime/Realm.h>
#include <LibJS/Runtime/Shape.h>
#include <LibJS/Runtime/TypedArray.h>
@@ -85,13 +86,17 @@ int main()
// ExecutionContext layout
outln("\n# ExecutionContext layout");
EMIT_OFFSET(EXECUTION_CONTEXT_EXECUTABLE, ExecutionContext, executable);
EMIT_OFFSET(EXECUTION_CONTEXT_GLOBAL_OBJECT, ExecutionContext, global_object);
EMIT_OFFSET(EXECUTION_CONTEXT_GLOBAL_DECLARATIVE_ENVIRONMENT, ExecutionContext, global_declarative_environment);
EMIT_OFFSET(EXECUTION_CONTEXT_REALM, ExecutionContext, realm);
EMIT_OFFSET(EXECUTION_CONTEXT_LEXICAL_ENVIRONMENT, ExecutionContext, lexical_environment);
EMIT_OFFSET(EXECUTION_CONTEXT_CALLER_FRAME, ExecutionContext, caller_frame);
EMIT_OFFSET(EXECUTION_CONTEXT_PROGRAM_COUNTER, ExecutionContext, program_counter);
EMIT_SIZEOF(SIZEOF_EXECUTION_CONTEXT, ExecutionContext);
// Realm layout
outln("\n# Realm layout");
EMIT_OFFSET(REALM_GLOBAL_OBJECT, Realm, m_global_object);
EMIT_OFFSET(REALM_GLOBAL_DECLARATIVE_ENVIRONMENT, Realm, m_global_declarative_environment);
// Interpreter layout
outln("\n# Interpreter layout");
EMIT_OFFSET(INTERPRETER_RUNNING_EXECUTION_CONTEXT, Interpreter, m_running_execution_context);