Reviewers: Weiliang,
Message:
wl.
please review and commit this patch.
thanks.
Description:
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
Please review this at https://codereview.chromium.org/330133004/
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files (+8, -5 lines):
M src/x87/lithium-codegen-x87.cc
Index: src/x87/lithium-codegen-x87.cc
===================================================================
--- src/x87/lithium-codegen-x87.cc (revision 21827)
+++ src/x87/lithium-codegen-x87.cc (working copy)
@@ -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;
}
--
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
---
You received this message because you are subscribed to the Google Groups "v8-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
