Improve integer division on IA32 and X64

Improve integer division on IA32 and X64
If the divisor is a Power-of-2 constant, we could use shifts instead of the
expensive idiv instructions, which also loose the register constraints.

Committed: https://code.google.com/p/v8/source/detail?r=13178

[Yang, 2012-12-10 09:47:28]

LGTM if comments are addressed.

https://codereview.chromium.org/11478043/diff/1/src/ia32/lithium-codegen-ia32.cc
File src/ia32/lithium-codegen-ia32.cc (right):

https://codereview.chromium.org/11478043/diff/1/src/ia32/lithium-codegen-ia32...
src/ia32/lithium-codegen-ia32.cc:1229: if (test_value != 0) {
this if-block seems also unnecessary if divisor is -1 or 1

https://codereview.chromium.org/11478043/diff/1/src/x64/lithium-codegen-x64.cc
File src/x64/lithium-codegen-x64.cc (right):

https://codereview.chromium.org/11478043/diff/1/src/x64/lithium-codegen-x64.c...
src/x64/lithium-codegen-x64.cc:1161: if (test_value != 0) {
Ditto.

[yuqiang.xian%intel.com, 2012-12-10 10:26:01]

Yang, thanks for the review. But I think the "test_value != 0" test does exclude
the cases where the divisor is -1 or 1, doesn't it?

[Yang, 2012-12-10 10:27:28]

On 2012/12/10 10:26:01, yuqiang.xian%intel.com wrote:
> Yang, thanks for the review. But I think the "test_value != 0" test does
exclude
> the cases where the divisor is -1 or 1, doesn't it?

Ah. My mistake. I'll land it then.