Revision: 20553
Author: [email protected]
Date: Mon Apr 7 16:37:30 2014 UTC
Log: MIPS: Fixed flooring division by -1.
Port r20544 (a64196c)
Original commit message:
We should avoid ASR #0 on ARM. Simplified and improved code a bit
while we're there on all platforms. Human brains are very bad at
understanding nested structures...
BUG=v8:3259
LOG=y
[email protected]
Review URL: https://codereview.chromium.org/227583003
Patch from Balazs Kilvady <[email protected]>.
http://code.google.com/p/v8/source/detail?r=20553
Modified:
/branches/bleeding_edge/src/mips/lithium-codegen-mips.cc
=======================================
--- /branches/bleeding_edge/src/mips/lithium-codegen-mips.cc Thu Apr 3
23:34:28 2014 UTC
+++ /branches/bleeding_edge/src/mips/lithium-codegen-mips.cc Mon Apr 7
16:37:30 2014 UTC
@@ -1322,25 +1322,27 @@
if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
DeoptimizeIf(eq, instr->environment(), result, Operand(zero_reg));
}
- if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
- // Note that we could emit branch-free code, but that would need one
more
- // register.
- __ Xor(at, scratch, result);
- if (divisor == -1) {
- DeoptimizeIf(ge, instr->environment(), at, Operand(zero_reg));
- __ sra(result, dividend, shift);
- } else {
- Label no_overflow, done;
- __ Branch(&no_overflow, lt, at, Operand(zero_reg));
- __ li(result, Operand(kMinInt / divisor));
- __ Branch(&done);
- __ bind(&no_overflow);
- __ sra(result, dividend, shift);
- __ bind(&done);
- }
- } else {
+
+ // If the negation could not overflow, simply shifting is OK.
+ if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
__ sra(result, dividend, shift);
+ return;
+ }
+
+ // Dividing by -1 is basically negation, unless we overflow.
+ __ Xor(at, scratch, result);
+ if (divisor == -1) {
+ DeoptimizeIf(ge, instr->environment(), at, Operand(zero_reg));
+ return;
}
+
+ Label no_overflow, done;
+ __ Branch(&no_overflow, lt, at, Operand(zero_reg));
+ __ li(result, Operand(kMinInt / divisor));
+ __ Branch(&done);
+ __ bind(&no_overflow);
+ __ sra(result, dividend, shift);
+ __ bind(&done);
}
--
--
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