Fix three bugs with handling negative zero in the optimizing compiler.

Fix three bugs with handling negative zero in the optimizing compiler.

* Bug fix for range analysis (contributed by Andy Wingo). Ranges of
double values have to include negative zero. Original code review:
 http://codereview.chromium.org/7514040/

* Fix a bug in optimized Math.round on ARM. When emitting minus-zero checks
we previously return a wrong result because of incorrect register assignment.

* Fix performance problem in IA32 and x64. Refine the checks
for minus zero and avoid unnecessary deoptimizations on Math.floor.

* Improve mjsunit test for Math.round to make sure we also
 get the optimized version of the code for each test case.
Committed: http://code.google.com/p/v8/source/detail?r=8877

[Kevin Millikin (Chromium), 2011-08-10 12:03:51]

LGTM.

http://codereview.chromium.org/7604028/diff/6002/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

http://codereview.chromium.org/7604028/diff/6002/src/arm/lithium-codegen-arm....
src/arm/lithium-codegen-arm.cc:3017: Register scratch2 = scratch0();
It doesn't really make sense to have scratch2 when there is no scratch1 (and
have it be an alias for scratch0!).  Maybe call it scratch?

http://codereview.chromium.org/7604028/diff/6002/src/ia32/lithium-codegen-ia3...
File src/ia32/lithium-codegen-ia32.cc (right):

http://codereview.chromium.org/7604028/diff/6002/src/ia32/lithium-codegen-ia3...
src/ia32/lithium-codegen-ia32.cc:2770: __ movmskpd(output_reg, input_reg);
Gesundheit.

[fschneider, 2011-08-10 12:33:16]

http://codereview.chromium.org/7604028/diff/6002/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

http://codereview.chromium.org/7604028/diff/6002/src/arm/lithium-codegen-arm....
src/arm/lithium-codegen-arm.cc:3017: Register scratch2 = scratch0();
On 2011/08/10 12:03:53, Kevin Millikin wrote:
> It doesn't really make sense to have scratch2 when there is no scratch1 (and
> have it be an alias for scratch0!).  Maybe call it scratch?

Done.

http://codereview.chromium.org/7604028/diff/6002/src/ia32/lithium-codegen-ia3...
File src/ia32/lithium-codegen-ia32.cc (right):

http://codereview.chromium.org/7604028/diff/6002/src/ia32/lithium-codegen-ia3...
src/ia32/lithium-codegen-ia32.cc:2770: __ movmskpd(output_reg, input_reg);
On 2011/08/10 12:03:53, Kevin Millikin wrote:
> Gesundheit.

Danke!