Revision: 21829
Author: [email protected]
Date: Fri Jun 13 07:03:11 2014 UTC
Log: X87: Fixed flooring division by a power of 2, once again...
port r21769
original message:
Avoid right shifts by zero bits: On ARM it actually means shifting by
32 bits (correctness issue) and on other platforms they are useless
(performance issue). This is fix for the fix in r20544.
BUG=v8:3259
LOG=y
[email protected]
Review URL: https://codereview.chromium.org/330133004
http://code.google.com/p/v8/source/detail?r=21829
Modified:
/branches/bleeding_edge/src/x87/lithium-codegen-x87.cc
=======================================
--- /branches/bleeding_edge/src/x87/lithium-codegen-x87.cc Wed Jun 11
09:09:15 2014 UTC
+++ /branches/bleeding_edge/src/x87/lithium-codegen-x87.cc Fri Jun 13
07:03:11 2014 UTC
@@ -1546,14 +1546,17 @@
DeoptimizeIf(zero, instr->environment());
}
- if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
- __ sar(dividend, shift);
+ // Dividing by -1 is basically negation, unless we overflow.
+ if (divisor == -1) {
+ if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ DeoptimizeIf(overflow, instr->environment());
+ }
return;
}
- // Dividing by -1 is basically negation, unless we overflow.
- if (divisor == -1) {
- DeoptimizeIf(overflow, instr->environment());
+ // If the negation could not overflow, simply shifting is OK.
+ if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
+ __ sar(dividend, shift);
return;
}
--
--
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