Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: ee963cf3db75e4ef1dfbdecdebce8fc7e5e52251
https://github.com/WebKit/WebKit/commit/ee963cf3db75e4ef1dfbdecdebce8fc7e5e52251
Author: Sosuke Suzuki <[email protected]>
Date: 2026-03-03 (Tue, 03 Mar 2026)
Changed paths:
A JSTests/stress/conditional-in-condition-context.js
M Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp
M Source/JavaScriptCore/parser/Nodes.h
Log Message:
-----------
[JSC] Add emitBytecodeInConditionContext for ConditionalNode
https://bugs.webkit.org/show_bug.cgi?id=308512
Reviewed by Keith Miller.
When a ternary expression (a ? b : c) appears in a condition context
(e.g., if/while/for conditions, logical operator operands), the bytecode
generator previously fell back to
ExpressionNode::emitBytecodeInConditionContext,
which materializes the ternary result into a temporary register and then
branches on it. This is redundant because the caller only needs to know
whether the result is truthy or falsy.
This patch adds ConditionalNode::emitBytecodeInConditionContext, which
propagates the condition context directly to m_expr1 and m_expr2,
allowing them to jump straight to the caller's true/false targets
without materializing an intermediate value.
For `if (a ? b : c) return 1; return 0;`, before:
enter
jfalse arg1, @else
mov loc5, arg2 // materialize b into temp
jmp @afterTernary
@else:
mov loc5, arg3 // materialize c into temp
@afterTernary:
jfalse loc5, @ifFalse // redundant branch on temp
ret 1
@ifFalse:
ret 0
After:
enter
jfalse arg1, @else
jfalse arg2, @ifFalse // branch directly on b
jmp @end
@else:
jfalse arg3, @ifFalse // branch directly on c
@end:
ret 1
@ifFalse:
ret 0
This eliminates 1 instruction and 1 temporary register in the basic
case. The optimization also chains recursively with existing condition
context nodes: ConstantNode (e.g., `a ? true : false` saves 2
instructions), LogicalOpNode (e.g., `a ? b && c : d || e` saves 3
instructions), LogicalNotNode, and nested ConditionalNodes.
Test: JSTests/stress/conditional-in-condition-context.js
* JSTests/stress/conditional-in-condition-context.js: Added.
(shouldBe):
(testBasic):
(testConstantThen):
(testConstantElse):
(testLogicalNot):
(testLogicalAnd):
(testNested):
(testWhile):
(testFor):
(testLogicalOperand):
(testLogicalOr):
(testDoWhile):
* Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp:
(JSC::ConditionalNode::emitBytecodeInConditionContext):
* Source/JavaScriptCore/parser/Nodes.h:
Canonical link: https://commits.webkit.org/308606@main
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