Changeset 264504 in webkit for trunk/Source/JavaScriptCore/bytecode/BytecodeUseDef.cpp

Timestamp:

Jul 17, 2020, 4:55:52 AM (5 years ago)

Author:

Alexey Shvayka

Message:

emitIsUndefined() should not special-case IsHTMLDDA objects
​https://bugs.webkit.org/show_bug.cgi?id=214443

Reviewed by Yusuke Suzuki.

JSTests:

• microbenchmarks/default-value-destructuring-array.js: Added.
• microbenchmarks/default-value-destructuring-object.js: Added.
• microbenchmarks/default-value-function-parameters.js: Added.
• stress/default-value-masquerader.js: Added.
• test262/expectations.yaml: Mark 10 test cases as passing.

Source/JavaScriptCore:

According to Annex B [1], there is only a handful of language constructs
that handle IsHTMLDDA objects: ToBoolean, abstract equality with null
or undefined, and typeof. Currently, op_is_undefined does special-case
masquarader objects, even though it is used beyond typeof.

With this change, emitIsUndefined() produces === undefined, which meets
developer expectations and the spec for all its usages, while op_is_undefined
is renamed to op_typeof_is_undefined. New name offers better semantics and
clearly communicates the op should be avoided when implementing new features.

Apart from fixing default values with IsHTMLDDA objects [2], this change
brings significant speed-up: +50% for function parameters and +20% for
object destructuring (masqueradesAsUndefinedWatchpoint is not fired).

This patch also introduces similar emitIsNull() method to avoid breaking
masquarader object as superclass test262 case.

[1]: ​https://tc39.es/ecma262/#sec-IsHTMLDDA-internal-slot
[2]: ​https://tc39.es/ecma262/#sec-runtime-semantics-keyedbindinginitialization (step 2)

• bytecode/BytecodeList.rb:
• bytecode/BytecodeUseDef.cpp:

(JSC::computeUsesForBytecodeIndexImpl):
(JSC::computeDefsForBytecodeIndexImpl):

• bytecompiler/BytecodeGenerator.cpp:

(JSC::BytecodeGenerator::emitEqualityOpImpl):
(JSC::BytecodeGenerator::emitIsUndefined): Deleted.

• bytecompiler/BytecodeGenerator.h:

(JSC::BytecodeGenerator::emitIsNull):
(JSC::BytecodeGenerator::emitIsUndefined):

• bytecompiler/NodesCodegen.cpp:

(JSC::ForInNode::emitBytecode):
(JSC::ClassExprNode::emitBytecode):

• dfg/DFGAbstractInterpreterInlines.h:

(JSC::DFG::AbstractInterpreter<AbstractStateType>::executeEffects):

• dfg/DFGByteCodeParser.cpp:

(JSC::DFG::ByteCodeParser::parseBlock):

• dfg/DFGCapabilities.cpp:

(JSC::DFG::capabilityLevel):

• dfg/DFGClobberize.h:

(JSC::DFG::clobberize):

• dfg/DFGDoesGC.cpp:

(JSC::DFG::doesGC):

• dfg/DFGFixupPhase.cpp:

(JSC::DFG::FixupPhase::fixupNode):

• dfg/DFGNodeType.h:
• dfg/DFGPredictionPropagationPhase.cpp:
• dfg/DFGSafeToExecute.h:

(JSC::DFG::safeToExecute):

• dfg/DFGSpeculativeJIT32_64.cpp:

(JSC::DFG::SpeculativeJIT::compile):

• dfg/DFGSpeculativeJIT64.cpp:

(JSC::DFG::SpeculativeJIT::compile):

• dfg/DFGWatchpointCollectionPhase.cpp:

(JSC::DFG::WatchpointCollectionPhase::handle):

• ftl/FTLCapabilities.cpp:

(JSC::FTL::canCompile):

• ftl/FTLLowerDFGToB3.cpp:

(JSC::FTL::DFG::LowerDFGToB3::compileNode):
(JSC::FTL::DFG::LowerDFGToB3::compileTypeOfIsUndefined):
(JSC::FTL::DFG::LowerDFGToB3::compileIsUndefined): Deleted.

• jit/JIT.cpp:

(JSC::JIT::privateCompileMainPass):

• jit/JIT.h:
• jit/JITOpcodes.cpp:

(JSC::JIT::emit_op_typeof_is_undefined):
(JSC::JIT::emit_op_is_undefined): Deleted.

• jit/JITOpcodes32_64.cpp:

(JSC::JIT::emit_op_typeof_is_undefined):
(JSC::JIT::emit_op_is_undefined): Deleted.

• llint/LowLevelInterpreter32_64.asm:
• llint/LowLevelInterpreter64.asm:

File:

• trunk/Source/JavaScriptCore/bytecode/BytecodeUseDef.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/bytecode/BytecodeUseDef.cpp

@@ -183 +183 @@
     USES(OpTypeof, value)
     USES(OpIsEmpty, operand)
-    USES(OpIsUndefined, operand)
+    USES(OpTypeofIsUndefined, operand)
     USES(OpIsUndefinedOrNull, operand)
     USES(OpIsBoolean, operand)
@@ -490 +490 @@
     DEFS(OpIdentityWithProfile, srcDst)
     DEFS(OpIsEmpty, dst)
-    DEFS(OpIsUndefined, dst)
+    DEFS(OpTypeofIsUndefined, dst)
     DEFS(OpIsUndefinedOrNull, dst)
     DEFS(OpIsBoolean, dst)