- Revision
- 199866
- Author
- commit-qu...@webkit.org
- Date
- 2016-04-21 21:46:53 -0700 (Thu, 21 Apr 2016)
Log Message
[JSC] Commute FDiv-by-constant into FMul-by-reciprocal when it is safe
https://bugs.webkit.org/show_bug.cgi?id=156871
Patch by Benjamin Poulain <bpoul...@webkit.org> on 2016-04-21
Reviewed by Filip Pizlo.
FMul is significantly faster than FDiv.
For example, on Haswell, FMul has a latency of 5, a throughput of 1
while FDiv has latency 10-24, throughput 8-18.
Fortunately for us, Sunspider and Kraken have plenty of division
by a simple power of 2 constant. Those are just exponent operations
and can be easily reversed to use FMul instead of FDiv.
LLVM does something similar in InstCombine.
* dfg/DFGStrengthReductionPhase.cpp:
(JSC::DFG::StrengthReductionPhase::handleNode):
* jit/JITDivGenerator.cpp:
(JSC::JITDivGenerator::loadOperand):
(JSC::JITDivGenerator::generateFastPath):
* jit/SnippetOperand.h:
(JSC::SnippetOperand::asConstNumber):
* runtime/MathCommon.h:
(JSC::safeReciprocalForDivByConst):
* tests/stress/floating-point-div-to-mul.js: Added.
(opaqueDivBy2):
(opaqueDivBy3):
(opaqueDivBy4):
(opaqueDivBySafeMaxMinusOne):
(opaqueDivBySafeMax):
(opaqueDivBySafeMaxPlusOne):
(opaqueDivBySafeMin):
(opaqueDivBySafeMinMinusOne):
(i.catch):
(i.result.opaqueDivBySafeMin.valueOf):
Modified Paths
Added Paths
Diff
Modified: trunk/Source/_javascript_Core/ChangeLog (199865 => 199866)
--- trunk/Source/_javascript_Core/ChangeLog 2016-04-22 04:29:02 UTC (rev 199865)
+++ trunk/Source/_javascript_Core/ChangeLog 2016-04-22 04:46:53 UTC (rev 199866)
@@ -1,3 +1,41 @@
+2016-04-21 Benjamin Poulain <bpoul...@webkit.org>
+
+ [JSC] Commute FDiv-by-constant into FMul-by-reciprocal when it is safe
+ https://bugs.webkit.org/show_bug.cgi?id=156871
+
+ Reviewed by Filip Pizlo.
+
+ FMul is significantly faster than FDiv.
+ For example, on Haswell, FMul has a latency of 5, a throughput of 1
+ while FDiv has latency 10-24, throughput 8-18.
+
+ Fortunately for us, Sunspider and Kraken have plenty of division
+ by a simple power of 2 constant. Those are just exponent operations
+ and can be easily reversed to use FMul instead of FDiv.
+
+ LLVM does something similar in InstCombine.
+
+ * dfg/DFGStrengthReductionPhase.cpp:
+ (JSC::DFG::StrengthReductionPhase::handleNode):
+ * jit/JITDivGenerator.cpp:
+ (JSC::JITDivGenerator::loadOperand):
+ (JSC::JITDivGenerator::generateFastPath):
+ * jit/SnippetOperand.h:
+ (JSC::SnippetOperand::asConstNumber):
+ * runtime/MathCommon.h:
+ (JSC::safeReciprocalForDivByConst):
+ * tests/stress/floating-point-div-to-mul.js: Added.
+ (opaqueDivBy2):
+ (opaqueDivBy3):
+ (opaqueDivBy4):
+ (opaqueDivBySafeMaxMinusOne):
+ (opaqueDivBySafeMax):
+ (opaqueDivBySafeMaxPlusOne):
+ (opaqueDivBySafeMin):
+ (opaqueDivBySafeMinMinusOne):
+ (i.catch):
+ (i.result.opaqueDivBySafeMin.valueOf):
+
2016-04-21 Benjamin Poulain <benja...@webkit.org>
[JSC] Improve the absThunkGenerator() for 64bit
Modified: trunk/Source/_javascript_Core/dfg/DFGStrengthReductionPhase.cpp (199865 => 199866)
--- trunk/Source/_javascript_Core/dfg/DFGStrengthReductionPhase.cpp 2016-04-22 04:29:02 UTC (rev 199865)
+++ trunk/Source/_javascript_Core/dfg/DFGStrengthReductionPhase.cpp 2016-04-22 04:46:53 UTC (rev 199866)
@@ -36,6 +36,7 @@
#include "DFGPredictionPropagationPhase.h"
#include "DFGVariableAccessDataDump.h"
#include "JSCInlines.h"
+#include "MathCommon.h"
#include "RegExpConstructor.h"
#include "StringPrototype.h"
#include <cstdlib>
@@ -192,6 +193,25 @@
}
break;
+ case ArithDiv:
+ // Transform
+ // ArithDiv(x, constant)
+ // Into
+ // ArithMul(x, 1 / constant)
+ // if the operation has the same result.
+ if (m_node->isBinaryUseKind(DoubleRepUse)
+ && m_node->child2()->isNumberConstant()) {
+
+ if (Optional<double> reciprocal = safeReciprocalForDivByConst(m_node->child2()->asNumber())) {
+ Node* reciprocalNode = m_insertionSet.insertConstant(m_nodeIndex, m_node->origin, jsDoubleNumber(*reciprocal), DoubleConstant);
+ m_node->setOp(ArithMul);
+ m_node->child2() = Edge(reciprocalNode, DoubleRepUse);
+ m_changed = true;
+ break;
+ }
+ }
+ break;
+
case ValueRep:
case Int52Rep:
case DoubleRep: {
Modified: trunk/Source/_javascript_Core/jit/JITDivGenerator.cpp (199865 => 199866)
--- trunk/Source/_javascript_Core/jit/JITDivGenerator.cpp 2016-04-22 04:29:02 UTC (rev 199865)
+++ trunk/Source/_javascript_Core/jit/JITDivGenerator.cpp 2016-04-22 04:46:53 UTC (rev 199866)
@@ -29,12 +29,17 @@
#if ENABLE(JIT)
#include "JSCJSValueInlines.h"
+#include "MathCommon.h"
namespace JSC {
void JITDivGenerator::loadOperand(CCallHelpers& jit, SnippetOperand& opr, JSValueRegs oprRegs, FPRReg destFPR)
{
if (opr.isConstInt32()) {
+ // FIXME: this does not looks right.
+ // -On x86_64, CVTSI2SD has partial register stall on its FPR.
+ // A move or load might be a tiny bit larger but safer.
+ // -On ARM64 we also have FMOV that can load small immediates.
jit.move(CCallHelpers::Imm32(opr.asConstInt32()), m_scratchGPR);
jit.convertInt32ToDouble(m_scratchGPR, destFPR);
#if USE(JSVALUE64)
@@ -74,10 +79,27 @@
ASSERT(!m_leftOperand.isConstInt32() || !m_rightOperand.isConstInt32());
m_didEmitFastPath = true;
loadOperand(jit, m_leftOperand, m_left, m_leftFPR);
- loadOperand(jit, m_rightOperand, m_right, m_rightFPR);
- jit.divDouble(m_rightFPR, m_leftFPR);
+#if USE(JSVALUE64)
+ Optional<double> safeReciprocal;
+ if (m_rightOperand.isConst()) {
+ double constant = m_rightOperand.asConstNumber();
+ safeReciprocal = safeReciprocalForDivByConst(constant);
+ }
+ if (safeReciprocal) {
+ jit.move(CCallHelpers::Imm64(bitwise_cast<int64_t>(*safeReciprocal)), m_scratchGPR);
+ jit.move64ToDouble(m_scratchGPR, m_rightFPR);
+
+ jit.mulDouble(m_rightFPR, m_leftFPR);
+ } else
+#endif
+ {
+ loadOperand(jit, m_rightOperand, m_right, m_rightFPR);
+
+ jit.divDouble(m_rightFPR, m_leftFPR);
+ }
+
// Is the result actually an integer? The DFG JIT would really like to know. If it's
// not an integer, we increment a count. If this together with the slow case counter
// are below threshold then the DFG JIT will compile this division with a speculation
Modified: trunk/Source/_javascript_Core/jit/SnippetOperand.h (199865 => 199866)
--- trunk/Source/_javascript_Core/jit/SnippetOperand.h 2016-04-22 04:29:02 UTC (rev 199865)
+++ trunk/Source/_javascript_Core/jit/SnippetOperand.h 2016-04-22 04:46:53 UTC (rev 199866)
@@ -70,6 +70,14 @@
return m_val.doubleVal;
}
+ double asConstNumber() const
+ {
+ if (isConstInt32())
+ return asConstInt32();
+ ASSERT(isConstDouble());
+ return asConstDouble();
+ }
+
void setConstInt32(int32_t value)
{
m_type = ConstInt32;
Modified: trunk/Source/_javascript_Core/runtime/MathCommon.h (199865 => 199866)
--- trunk/Source/_javascript_Core/runtime/MathCommon.h 2016-04-22 04:29:02 UTC (rev 199865)
+++ trunk/Source/_javascript_Core/runtime/MathCommon.h 2016-04-22 04:46:53 UTC (rev 199866)
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2015 Apple Inc. All rights reserved.
+ * Copyright (C) 2015-2016 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@@ -27,6 +27,7 @@
#define MathCommon_h
#include "JITOperations.h"
+#include <wtf/Optional.h>
#ifndef JIT_OPERATION
#define JIT_OPERATION
@@ -54,6 +55,34 @@
#endif
}
+inline Optional<double> safeReciprocalForDivByConst(double constant)
+{
+ // No "weird" numbers (NaN, Denormal, etc).
+ if (!constant || !isnormal(constant))
+ return Nullopt;
+
+ int exponent;
+ if (frexp(constant, &exponent) != 0.5)
+ return Nullopt;
+
+ // Note that frexp() returns the value divided by two
+ // so we to offset this exponent by one.
+ exponent -= 1;
+
+ // A double exponent is between -1022 and 1023.
+ // Nothing we can do to invert 1023.
+ if (exponent == 1023)
+ return Nullopt;
+
+ double reciprocal = ldexp(1, -exponent);
+ ASSERT(isnormal(reciprocal));
+ ASSERT(1. / constant == reciprocal);
+ ASSERT(constant == 1. / reciprocal);
+ ASSERT(1. == constant * reciprocal);
+
+ return reciprocal;
+}
+
extern "C" {
double JIT_OPERATION jsRound(double value) REFERENCED_FROM_ASM WTF_INTERNAL;
}
Added: trunk/Source/_javascript_Core/tests/stress/floating-point-div-to-mul.js (0 => 199866)
--- trunk/Source/_javascript_Core/tests/stress/floating-point-div-to-mul.js (rev 0)
+++ trunk/Source/_javascript_Core/tests/stress/floating-point-div-to-mul.js 2016-04-22 04:46:53 UTC (rev 199866)
@@ -0,0 +1,216 @@
+function opaqueDivBy2(a)
+{
+ return a / 2;
+}
+noInline(opaqueDivBy2);
+
+function opaqueDivBy3(a)
+{
+ return a / 3;
+}
+noInline(opaqueDivBy3);
+
+function opaqueDivBy4(a)
+{
+ return a / 4;
+}
+noInline(opaqueDivBy4);
+
+function opaqueDivBySafeMaxMinusOne(a)
+{
+ // 2^1022
+ return a / 44942328371557897693232629769725618340449424473557664318357520289433168951375240783177119330601884005280028469967848339414697442203604155623211857659868531094441973356216371319075554900311523529863270738021251442209537670585615720368478277635206809290837627671146574559986811484619929076208839082406056034304;
+}
+noInline(opaqueDivBySafeMaxMinusOne);
+
+function opaqueDivBySafeMax(a)
+{
+ // 2^1023
+ return a / 89884656743115795386465259539451236680898848947115328636715040578866337902750481566354238661203768010560056939935696678829394884407208311246423715319737062188883946712432742638151109800623047059726541476042502884419075341171231440736956555270413618581675255342293149119973622969239858152417678164812112068608;
+}
+noInline(opaqueDivBySafeMax);
+
+function opaqueDivBySafeMaxPlusOne(a)
+{
+ // 2^1024
+ return a / 179769313486231590772930519078902473361797697894230657273430081157732675805500963132708477322407536021120113879871393357658789768814416622492847430639474124377767893424865485276302219601246094119453082952085005768838150682342462881473913110540827237163350510684586298239947245938479716304835356329624224137216;
+}
+noInline(opaqueDivBySafeMaxPlusOne);
+
+function opaqueDivBySafeMin(a)
+{
+ // 2^-1022
+ return a / (1 / 44942328371557897693232629769725618340449424473557664318357520289433168951375240783177119330601884005280028469967848339414697442203604155623211857659868531094441973356216371319075554900311523529863270738021251442209537670585615720368478277635206809290837627671146574559986811484619929076208839082406056034304);
+}
+noInline(opaqueDivBySafeMin);
+
+function opaqueDivBySafeMinMinusOne(a)
+{
+ // 2^-1023
+ return a / (1 / 89884656743115795386465259539451236680898848947115328636715040578866337902750481566354238661203768010560056939935696678829394884407208311246423715319737062188883946712432742638151109800623047059726541476042502884419075341171231440736956555270413618581675255342293149119973622969239858152417678164812112068608);
+}
+noInline(opaqueDivBySafeMinMinusOne);
+
+
+for (let i = 0; i < 1e4; ++i) {
+ let result = opaqueDivBy2(Math.PI);
+ if (result !== 1.5707963267948966)
+ throw "Failed opaqueDivBy2(Math.PI). Result = " + result;
+ result = opaqueDivBy2(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBy2(NaN). Result = " + result;
+ result = opaqueDivBy2(Infinity);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBy2(Infinity). Result = " + result;
+ result = opaqueDivBy2(-Infinity);
+ if (result !== -Infinity)
+ throw "Failed opaqueDivBy2(-Infinity). Result = " + result;
+ result = opaqueDivBy2(Math.E);
+ if (result !== 1.3591409142295225)
+ throw "Failed opaqueDivBy2(Math.E). Result = " + result;
+
+ result = opaqueDivBy3(Math.PI);
+ if (result !== 1.0471975511965976)
+ throw "Failed opaqueDivBy3(Math.PI). Result = " + result;
+ result = opaqueDivBy3(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBy3(NaN). Result = " + result;
+ result = opaqueDivBy3(Infinity);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBy3(Infinity). Result = " + result;
+ result = opaqueDivBy3(-Infinity);
+ if (result !== -Infinity)
+ throw "Failed opaqueDivBy3(-Infinity). Result = " + result;
+ result = opaqueDivBy3(Math.E);
+ if (result !== 0.9060939428196817)
+ throw "Failed opaqueDivBy3(Math.E). Result = " + result;
+
+ result = opaqueDivBy4(Math.PI);
+ if (result !== 0.7853981633974483)
+ throw "Failed opaqueDivBy4(Math.PI). Result = " + result;
+ result = opaqueDivBy4(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBy4(NaN). Result = " + result;
+ result = opaqueDivBy4(Infinity);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBy4(Infinity). Result = " + result;
+ result = opaqueDivBy4(-Infinity);
+ if (result !== -Infinity)
+ throw "Failed opaqueDivBy4(-Infinity). Result = " + result;
+ result = opaqueDivBy4(Math.E);
+ if (result !== 0.6795704571147613)
+ throw "Failed opaqueDivBy4(Math.E). Result = " + result;
+
+ result = opaqueDivBySafeMaxMinusOne(Math.PI);
+ if (result !== 6.990275687580919e-308)
+ throw "Failed opaqueDivBySafeMaxMinusOne(Math.PI). Result = " + result;
+ result = opaqueDivBySafeMaxMinusOne(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBySafeMaxMinusOne(NaN). Result = " + result;
+ result = opaqueDivBySafeMaxMinusOne(Infinity);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBySafeMaxMinusOne(Infinity). Result = " + result;
+ result = opaqueDivBySafeMaxMinusOne(-Infinity);
+ if (result !== -Infinity)
+ throw "Failed opaqueDivBySafeMaxMinusOne(-Infinity). Result = " + result;
+ result = opaqueDivBySafeMaxMinusOne(Math.E);
+ if (result !== 6.048377836559378e-308)
+ throw "Failed opaqueDivBySafeMaxMinusOne(Math.E). Result = " + result;
+
+ result = opaqueDivBySafeMax(Math.PI);
+ if (result !== 3.4951378437904593e-308)
+ throw "Failed opaqueDivBySafeMax(Math.PI). Result = " + result;
+ result = opaqueDivBySafeMax(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBySafeMax(NaN). Result = " + result;
+ result = opaqueDivBySafeMax(Infinity);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBySafeMax(Infinity). Result = " + result;
+ result = opaqueDivBySafeMax(-Infinity);
+ if (result !== -Infinity)
+ throw "Failed opaqueDivBySafeMax(-Infinity). Result = " + result;
+ result = opaqueDivBySafeMax(Math.E);
+ if (result !== 3.024188918279689e-308)
+ throw "Failed opaqueDivBySafeMax(Math.E). Result = " + result;
+
+ result = opaqueDivBySafeMaxPlusOne(Math.PI);
+ if (result !== 0)
+ throw "Failed opaqueDivBySafeMaxPlusOne(Math.PI). Result = " + result;
+ result = opaqueDivBySafeMaxPlusOne(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBySafeMaxPlusOne(NaN). Result = " + result;
+ result = opaqueDivBySafeMaxPlusOne(Infinity);
+ if (result === result)
+ throw "Failed opaqueDivBySafeMaxPlusOne(Infinity). Result = " + result;
+ result = opaqueDivBySafeMaxPlusOne(-Infinity);
+ if (result === result)
+ throw "Failed opaqueDivBySafeMaxPlusOne(-Infinity). Result = " + result;
+ result = opaqueDivBySafeMaxPlusOne(Math.E);
+ if (result !== 0)
+ throw "Failed opaqueDivBySafeMaxPlusOne(Math.E). Result = " + result;
+
+ result = opaqueDivBySafeMin(Math.PI);
+ if (result !== 1.4119048864730642e+308)
+ throw "Failed opaqueDivBySafeMin(Math.PI). Result = " + result;
+ result = opaqueDivBySafeMin(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBySafeMin(NaN). Result = " + result;
+ result = opaqueDivBySafeMin(Infinity);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBySafeMin(Infinity). Result = " + result;
+ result = opaqueDivBySafeMin(-Infinity);
+ if (result !== -Infinity)
+ throw "Failed opaqueDivBySafeMin(-Infinity). Result = " + result;
+ result = opaqueDivBySafeMin(Math.E);
+ if (result !== 1.2216591454104522e+308)
+ throw "Failed opaqueDivBySafeMin(Math.E). Result = " + result;
+
+ result = opaqueDivBySafeMinMinusOne(Math.PI);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBySafeMinMinusOne(Math.PI). Result = " + result;
+ result = opaqueDivBySafeMinMinusOne(NaN);
+ if (result === result)
+ throw "Failed opaqueDivBySafeMinMinusOne(NaN). Result = " + result;
+ result = opaqueDivBySafeMinMinusOne(Infinity);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBySafeMinMinusOne(Infinity). Result = " + result;
+ result = opaqueDivBySafeMinMinusOne(-Infinity);
+ if (result !== -Infinity)
+ throw "Failed opaqueDivBySafeMinMinusOne(-Infinity). Result = " + result;
+ result = opaqueDivBySafeMinMinusOne(Math.E);
+ if (result !== Infinity)
+ throw "Failed opaqueDivBySafeMinMinusOne(Math.E). Result = " + result;
+}
+
+
+// Check that we don't do anything crazy with crazy types.
+for (let i = 0; i < 1e3; ++i) {
+ let result = opaqueDivBy2();
+ if (result === result)
+ throw "Failed opaqueDivBy2()";
+ result = opaqueDivBy4(null);
+ if (result !== 0)
+ throw "Failed opaqueDivBy4(null)";
+ result = opaqueDivBySafeMaxMinusOne("WebKit!");
+ if (result === result)
+ throw "Failed opaqueDivBy4(null)";
+ result = opaqueDivBySafeMin("");
+ if (result !== 0)
+ throw "Failed opaqueDivBySafeMin('')";
+ try {
+ result = opaqueDivBy2(Symbol());
+ throw "Failed opaqueDivBy2(Symbol())";
+ } catch (exception) {
+ if (exception != "TypeError: Type error")
+ throw "Wrong exception: " + exception;
+ }
+ result = opaqueDivBy4(true);
+ if (result !== 0.25)
+ throw "Failed opaqueDivBy4(true)";
+ result = opaqueDivBySafeMaxMinusOne(false);
+ if (result !== 0)
+ throw "Failed opaqueDivBySafeMaxMinusOne(false)";
+ result = opaqueDivBySafeMin({ valueOf: function() { return 42; }});
+ if (result !== Infinity)
+ throw "Failed opaqueDivBySafeMin({ valueOf: function() { return 42; }})";
+}
