Changeset 203499 in webkit for trunk/Source/JavaScriptCore/parser/Lexer.cpp

Timestamp:

Jul 21, 2016, 12:33:28 AM (9 years ago)

Author:

Yusuke Suzuki

Message:

[ES7] Introduce exponentiation expression
​https://bugs.webkit.org/show_bug.cgi?id=159969

Reviewed by Saam Barati.

This patch implements the exponentiation expression, e.g. x ** y.
The exponentiation expression is introduced in ECMA262 2016 and ECMA262 2016
is already released. So this is not the draft spec.

The exponentiation expression has 2 interesting points.

1. Right associative

To follow the Math expression, operator is right associative.
When we execute x ** y ** z, this is handled as x ** (y ** z), not (x ** y) ** z.
This patch introduces the right associativity to the binary operator and handles it
in the operator precedence parser in Parser.cpp.

2. LHS of the exponentiation expression is UpdateExpression

ExponentiationExpression[Yield]:

UnaryExpression?Yield
UpdateExpression?Yield ExponentiationExpression?Yield

As we can see, the left hand side of the ExponentiationExpression is UpdateExpression, not UnaryExpression.
It means that +x ** y becomes a syntax error. This is intentional. Without superscript in JS,
-x**y is confusing between -(x ** y) and (-x) ** y. So ECMA262 intentionally avoids UnaryExpression here.
If we need to use a negated value, we need to write parentheses explicitly e.g. (-x) ** y.
In this patch, we ensure that the left hand side is not an unary expression by checking an operator in
parseBinaryExpression. This works since ** has the highest operator precedence in the binary operators.

We introduce a new bytecode, op_pow. That simply works as similar as the other binary operators.
And it is converted to ArithPow in DFG and handled in DFG and FTL.
In this patch, we take the approach just introducing a new bytecode instead of calling Math.pow.
This is because we would like to execute ToNumber in the caller side, not in the callee (Math.pow) side.
And we don't want to compile into the following.

lhsNumber = to_number (lhs)
rhsNumber = to_number (rhs)
call Math.pow(lhsNumber, rhsNumber)

We ensure that this patch passes all the test262 tests related to the exponentiation expression.

The only sensitive part to the performance is the parser changes.
So we measured the code-load performance and it is neutral in my x64 Linux box (hanayamata).

Collected 30 samples per benchmark/VM, with 30 VM invocations per benchmark. Emitted a call to
gc() between sample measurements. Used 1 benchmark iteration per VM invocation for warm-up. Used
the jsc-specific preciseTime() function to get microsecond-level timing. Reporting benchmark
execution times with 95% confidence intervals in milliseconds.

baseline patched

closure 0.60499+-0.00250 0.60180+-0.00244
jquery 7.89175+-0.02433 ? 7.91287+-0.04759 ?

<geometric> 2.18499+-0.00523 2.18207+-0.00689 might be 1.0013x faster

• bytecode/BytecodeList.json:
• bytecode/BytecodeUseDef.h:

(JSC::computeUsesForBytecodeOffset):
(JSC::computeDefsForBytecodeOffset):

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::dumpBytecode):

• bytecompiler/NodesCodegen.cpp:

(JSC::emitReadModifyAssignment):

• dfg/DFGByteCodeParser.cpp:

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

• dfg/DFGCapabilities.cpp:

(JSC::DFG::capabilityLevel):

• jit/JIT.cpp:

(JSC::JIT::privateCompileMainPass):

• jit/JIT.h:
• jit/JITArithmetic.cpp:

(JSC::JIT::emit_op_pow):

• llint/LowLevelInterpreter.asm:
• parser/ASTBuilder.h:

(JSC::ASTBuilder::operatorStackShouldReduce):
(JSC::ASTBuilder::makePowNode):
(JSC::ASTBuilder::makeMultNode):
(JSC::ASTBuilder::makeDivNode):
(JSC::ASTBuilder::makeModNode):
(JSC::ASTBuilder::makeSubNode):
(JSC::ASTBuilder::makeBinaryNode):
(JSC::ASTBuilder::operatorStackHasHigherPrecedence): Deleted.

• parser/Lexer.cpp:

(JSC::Lexer<T>::lex):

• parser/NodeConstructors.h:

(JSC::PowNode::PowNode):

• parser/Nodes.h:
• parser/Parser.cpp:

(JSC::Parser<LexerType>::parseAssignmentExpression):
(JSC::isUnaryOpExcludingUpdateOp):
(JSC::Parser<LexerType>::parseBinaryExpression):
(JSC::isUnaryOp): Deleted.

• parser/ParserTokens.h:

(JSC::isUpdateOp):
(JSC::isUnaryOp):

• parser/SyntaxChecker.h:

(JSC::SyntaxChecker::operatorStackPop):

• runtime/CommonSlowPaths.cpp:

(JSC::SLOW_PATH_DECL):

• runtime/CommonSlowPaths.h:
• tests/stress/pow-basics.js: Added.

(valuesAreClose):
(mathPowDoubleDouble1):
(mathPowDoubleInt1):
(test1):
(mathPowDoubleDouble2):
(mathPowDoubleInt2):
(test2):
(mathPowDoubleDouble3):
(mathPowDoubleInt3):
(test3):
(mathPowDoubleDouble4):
(mathPowDoubleInt4):
(test4):
(mathPowDoubleDouble5):
(mathPowDoubleInt5):
(test5):
(mathPowDoubleDouble6):
(mathPowDoubleInt6):
(test6):
(mathPowDoubleDouble7):
(mathPowDoubleInt7):
(test7):
(mathPowDoubleDouble8):
(mathPowDoubleInt8):
(test8):
(mathPowDoubleDouble9):
(mathPowDoubleInt9):
(test9):
(mathPowDoubleDouble10):
(mathPowDoubleInt10):
(test10):
(mathPowDoubleDouble11):
(mathPowDoubleInt11):
(test11):

• tests/stress/pow-coherency.js: Added.

(pow42):
(build42AsDouble.opaqueAdd):
(build42AsDouble):
(powDouble42):
(clobber):
(pow42NoConstantFolding):
(powDouble42NoConstantFolding):

• tests/stress/pow-evaluation-order.js: Added.

(shouldBe):
(throw.new.Error):

• tests/stress/pow-expects-update-expression-on-lhs.js: Added.

(testSyntax):
(testSyntaxError):
(throw.new.Error):
(let.token.of.tokens.testSyntax.pow):
(testSyntax.pow):

• tests/stress/pow-integer-exponent-fastpath.js: Added.

(valuesAreClose):
(mathPowDoubleDoubleTestExponentFifty):
(mathPowDoubleIntTestExponentFifty):
(testExponentFifty):
(mathPowDoubleDoubleTestExponentTenThousands):
(mathPowDoubleIntTestExponentTenThousands):
(testExponentTenThousands):

• tests/stress/pow-nan-behaviors.js: Added.

(testIntegerBaseWithNaNExponentStatic):
(mathPowIntegerBaseWithNaNExponentDynamic):
(testIntegerBaseWithNaNExponentDynamic):
(testFloatingPointBaseWithNaNExponentStatic):
(mathPowFloatingPointBaseWithNaNExponentDynamic):
(testFloatingPointBaseWithNaNExponentDynamic):
(testNaNBaseStatic):
(mathPowNaNBaseDynamic1):
(mathPowNaNBaseDynamic2):
(mathPowNaNBaseDynamic3):
(mathPowNaNBaseDynamic4):
(testNaNBaseDynamic):
(infiniteExponentsStatic):
(mathPowInfiniteExponentsDynamic1):
(mathPowInfiniteExponentsDynamic2):
(mathPowInfiniteExponentsDynamic3):
(mathPowInfiniteExponentsDynamic4):
(infiniteExponentsDynamic):

• tests/stress/pow-simple.js: Added.

(shouldBe):
(throw.new.Error):

• tests/stress/pow-stable-results.js: Added.

(opaquePow):
(isIdentical):

• tests/stress/pow-to-number-should-be-executed-in-code-side.js: Added.

(shouldBe):
(throw.new.Error):

• tests/stress/pow-with-constants.js: Added.

(exponentIsZero):
(testExponentIsZero):
(exponentIsOne):
(testExponentIsOne):
(powUsedAsSqrt):
(testPowUsedAsSqrt):
(powUsedAsOneOverSqrt):
(testPowUsedAsOneOverSqrt):
(powUsedAsSquare):
(testPowUsedAsSquare):
(intIntConstantsSmallNumbers):
(intIntConstantsLargeNumbers):
(intIntSmallConstants):
(intDoubleConstants):
(doubleDoubleConstants):
(doubleIntConstants):
(testBaseAndExponentConstantLiterals):
(exponentIsIntegerConstant):
(testExponentIsIntegerConstant):
(exponentIsDoubleConstant):
(testExponentIsDoubleConstant):
(exponentIsInfinityConstant):
(testExponentIsInfinityConstant):
(exponentIsNegativeInfinityConstant):
(testExponentIsNegativeInfinityConstant):

• tests/stress/pow-with-never-NaN-exponent.js: Added.

(exponentIsNonNanDouble1):
(exponentIsNonNanDouble2):
(testExponentIsDoubleConstant):

• tests/test262.yaml:

File:

• trunk/Source/JavaScriptCore/parser/Lexer.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/parser/Lexer.cpp

@@ -1957 +1957 @@
             break;
         }
+        if (m_current == '*') {
+            shift();
+            if (m_current == '=') {
+                shift();
+                token = POWEQUAL;
+                break;
+            }
+            token = POW;
+            break;
+        }
         token = TIMES;
         break;