Reviewers: danno, Sven Panne, Paul Lind, kisg, palfia, dusmil,
Description:
MIPS: Implement flooring division by a constant via truncating division by a
constant.
Port r20123 (31ab416)
BUG=
Please review this at https://codereview.chromium.org/206373004/
SVN Base: https://github.com/v8/v8.git@gbl
Affected files (+42, -13 lines):
M src/mips/lithium-codegen-mips.cc
M src/mips/lithium-mips.h
M src/mips/lithium-mips.cc
Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc
b/src/mips/lithium-codegen-mips.cc
index
e306c174cf7b62b0168ccfc6d249cc6359787969..5e47665c0c3c4298e33d898341f41f50642d00bc
100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -1367,8 +1367,31 @@ void
LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
DeoptimizeIf(eq, instr->environment(), dividend, Operand(zero_reg));
}
- // TODO(svenpanne) Add correction terms.
- __ TruncatingDiv(result, dividend, divisor);
+ // Easy case: We need no dynamic check for the dividend and the flooring
+ // division is the same as the truncating division.
+ if ((divisor > 0 && !hdiv->CheckFlag(HValue::kLeftCanBeNegative)) ||
+ (divisor < 0 && !hdiv->CheckFlag(HValue::kLeftCanBePositive))) {
+ __ TruncatingDiv(result, dividend, Abs(divisor));
+ if (divisor < 0) __ Subu(result, zero_reg, result);
+ return;
+ }
+
+ // In the general case we may need to adjust before and after the
truncating
+ // division to get a flooring division.
+ Register temp = ToRegister(instr->temp());
+ ASSERT(!temp.is(dividend) && !temp.is(result));
+ Label needs_adjustment, done;
+ __ Branch(&needs_adjustment, divisor > 0 ? lt : gt,
+ dividend, Operand(zero_reg));
+ __ TruncatingDiv(result, dividend, Abs(divisor));
+ if (divisor < 0) __ Subu(result, zero_reg, result);
+ __ jmp(&done);
+ __ bind(&needs_adjustment);
+ __ Addu(temp, dividend, Operand(divisor > 0 ? 1 : -1));
+ __ TruncatingDiv(result, temp, Abs(divisor));
+ if (divisor < 0) __ Subu(result, zero_reg, result);
+ __ Subu(result, result, Operand(1));
+ __ bind(&done);
}
Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index
d2473fc4df69f6c4de53d27f9c6bba3f3796ed7d..752f67673d76841120c4a2b4be96fbef29ec84cd
100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1337,20 +1337,25 @@ LInstruction*
LChunkBuilder::DoFlooringDivByConstI(HMathFloorOfDiv* instr) {
ASSERT(instr->right()->representation().Equals(instr->representation()));
LOperand* dividend = UseRegister(instr->left());
int32_t divisor = instr->right()->GetInteger32Constant();
- LInstruction* result =
- DefineAsRegister(new(zone()) LFlooringDivByConstI(dividend,
divisor));
- bool can_deopt =
- divisor == 0 ||
- (instr->CheckFlag(HValue::kBailoutOnMinusZero) && divisor < 0);
- return can_deopt ? AssignEnvironment(result) : result;
+ LOperand* temp =
+ ((divisor > 0 && !instr->CheckFlag(HValue::kLeftCanBeNegative)) ||
+ (divisor < 0 && !instr->CheckFlag(HValue::kLeftCanBePositive))) ?
+ NULL : TempRegister();
+ LInstruction* result = DefineAsRegister(
+ new(zone()) LFlooringDivByConstI(dividend, divisor, temp));
+ if (divisor == 0 ||
+ (instr->CheckFlag(HValue::kBailoutOnMinusZero) && divisor < 0)) {
+ result = AssignEnvironment(result);
+ }
+ return result;
}
LInstruction* LChunkBuilder::DoMathFloorOfDiv(HMathFloorOfDiv* instr) {
if (instr->RightIsPowerOf2()) {
return DoFlooringDivByPowerOf2I(instr);
- } else if (false && instr->right()->IsConstant()) {
- return DoFlooringDivByConstI(instr); // TODO(svenpanne) Fix and
re-enable.
+ } else if (instr->right()->IsConstant()) {
+ return DoFlooringDivByConstI(instr);
} else {
return DoDivI(instr);
}
Index: src/mips/lithium-mips.h
diff --git a/src/mips/lithium-mips.h b/src/mips/lithium-mips.h
index
81f7fb67a424e07c11a50d29d252a41e6a59f06e..ae59e57f27f7a0c445948de12be9d541f77a64f9
100644
--- a/src/mips/lithium-mips.h
+++ b/src/mips/lithium-mips.h
@@ -741,16 +741,17 @@ class LFlooringDivByPowerOf2I V8_FINAL : public
LTemplateInstruction<1, 1, 0> {
};
-class LFlooringDivByConstI V8_FINAL : public LTemplateInstruction<1, 1, 0>
{
+class LFlooringDivByConstI V8_FINAL : public LTemplateInstruction<1, 1, 2>
{
public:
- LFlooringDivByConstI(LOperand* dividend, int32_t divisor) {
+ LFlooringDivByConstI(LOperand* dividend, int32_t divisor, LOperand*
temp) {
inputs_[0] = dividend;
divisor_ = divisor;
+ temps_[0] = temp;
}
LOperand* dividend() { return inputs_[0]; }
int32_t divisor() const { return divisor_; }
- LOperand* temp1() { return temps_[0]; }
+ LOperand* temp() { return temps_[0]; }
DECLARE_CONCRETE_INSTRUCTION(FlooringDivByConstI, "flooring-div-by-const-i")
DECLARE_HYDROGEN_ACCESSOR(MathFloorOfDiv)
--
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