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Unified Diff: src/x64/lithium-codegen-x64.cc

Issue 191293012: Reland "Handle non-power-of-2 divisors in division-like operations". (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: Created 6 years, 9 months ago
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Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 4dc9d4a34a9f49c6bf7c41679f522a2e188cdd45..1b6a97b22d2ddfa377ba85c1c45ffcfb2d373365 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1016,6 +1016,37 @@ void LCodeGen::DoModByPowerOf2I(LModByPowerOf2I* instr) {
}
+void LCodeGen::DoModByConstI(LModByConstI* instr) {
+ Register dividend = ToRegister(instr->dividend());
+ int32_t divisor = instr->divisor();
+ ASSERT(ToRegister(instr->result()).is(rax));
+
+ if (divisor == 0) {
+ DeoptimizeIf(no_condition, instr->environment());
+ return;
+ }
+
+ __ FlooringDiv(dividend, Abs(divisor));
+ __ movl(rax, dividend);
+ __ shrl(rax, Immediate(31));
+ __ addl(rdx, rax);
+ __ imull(rdx, rdx, Immediate(Abs(divisor)));
+ __ movl(rax, dividend);
+ __ subl(rax, rdx);
+
+ // Check for negative zero.
+ HMod* hmod = instr->hydrogen();
+ if (hmod->CheckFlag(HValue::kBailoutOnMinusZero) &&
+ hmod->left()->CanBeNegative()) {
+ Label remainder_not_zero;
+ __ j(not_zero, &remainder_not_zero, Label::kNear);
+ __ cmpl(dividend, Immediate(0));
+ DeoptimizeIf(less, instr->environment());
+ __ bind(&remainder_not_zero);
+ }
+}
+
+
void LCodeGen::DoModI(LModI* instr) {
if (instr->hydrogen()->RightIsPowerOf2()) {
return DoModByPowerOf2I(reinterpret_cast<LModByPowerOf2I*>(instr));
@@ -1119,42 +1150,22 @@ void LCodeGen::DoFlooringDivByPowerOf2I(LFlooringDivByPowerOf2I* instr) {
void LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
Register dividend = ToRegister(instr->dividend());
int32_t divisor = instr->divisor();
- Register temp = ToRegister(instr->temp());
- Register result = ToRegister(instr->result());
+ ASSERT(ToRegister(instr->result()).is(rdx));
if (divisor == 0) {
DeoptimizeIf(no_condition, instr->environment());
return;
}
- // Find b which: 2^b < divisor_abs < 2^(b+1).
- uint32_t divisor_abs = abs(divisor);
- unsigned b = 31 - CompilerIntrinsics::CountLeadingZeros(divisor_abs);
- unsigned shift = 32 + b; // Precision +1bit (effectively).
- double multiplier_f =
- static_cast<double>(static_cast<uint64_t>(1) << shift) / divisor_abs;
- int64_t multiplier;
- if (multiplier_f - std::floor(multiplier_f) < 0.5) {
- multiplier = static_cast<int64_t>(std::floor(multiplier_f));
- } else {
- multiplier = static_cast<int64_t>(std::floor(multiplier_f)) + 1;
- }
- // The multiplier is a uint32.
- ASSERT(multiplier > 0 &&
- multiplier < (static_cast<int64_t>(1) << 32));
- // The multiply is int64, so sign-extend to r64.
- __ movsxlq(temp, dividend);
- if (divisor < 0 &&
- instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
- __ neg(temp);
+ // Check for (0 / -x) that will produce negative zero.
+ HMathFloorOfDiv* hdiv = instr->hydrogen();
+ if (hdiv->CheckFlag(HValue::kBailoutOnMinusZero) &&
+ hdiv->left()->RangeCanInclude(0) && divisor < 0) {
+ __ testl(dividend, dividend);
DeoptimizeIf(zero, instr->environment());
}
- __ Set(result, multiplier);
- // Result just fit in r64, because it's int32 * uint32.
- __ imul(result, temp);
- __ addq(result, Immediate(1 << 30));
- __ sar(result, Immediate(shift));
+ __ FlooringDiv(dividend, divisor);
}
@@ -1198,6 +1209,39 @@ void LCodeGen::DoDivByPowerOf2I(LDivByPowerOf2I* instr) {
}
+void LCodeGen::DoDivByConstI(LDivByConstI* instr) {
+ Register dividend = ToRegister(instr->dividend());
+ int32_t divisor = instr->divisor();
+ ASSERT(ToRegister(instr->result()).is(rdx));
+
+ if (divisor == 0) {
+ DeoptimizeIf(no_condition, instr->environment());
+ return;
+ }
+
+ // Check for (0 / -x) that will produce negative zero.
+ HDiv* hdiv = instr->hydrogen();
+ if (hdiv->CheckFlag(HValue::kBailoutOnMinusZero) &&
+ hdiv->left()->RangeCanInclude(0) && divisor < 0) {
+ __ testl(dividend, dividend);
+ DeoptimizeIf(zero, instr->environment());
+ }
+
+ __ FlooringDiv(dividend, Abs(divisor));
+ __ movl(rax, dividend);
+ __ shrl(rax, Immediate(31));
+ __ addl(rdx, rax);
+ if (divisor < 0) __ neg(rdx);
+
+ if (!hdiv->CheckFlag(HInstruction::kAllUsesTruncatingToInt32)) {
+ __ movl(rax, rdx);
+ __ imull(rax, rax, Immediate(divisor));
+ __ subl(rax, dividend);
+ DeoptimizeIf(not_equal, instr->environment());
+ }
+}
+
+
void LCodeGen::DoDivI(LDivI* instr) {
Register dividend = ToRegister(instr->left());
Register divisor = ToRegister(instr->right());
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