Use movw/movt on ARM to load constant roots

Use movw/movt on ARM to load constant roots
BUG=none
TEST=none

Committed: https://code.google.com/p/v8/source/detail?r=12895

[danno, 2012-10-29 15:05:39]

http://codereview.chromium.org/11307012/diff/1/src/arm/macro-assembler-arm.cc
File src/arm/macro-assembler-arm.cc (right):

http://codereview.chromium.org/11307012/diff/1/src/arm/macro-assembler-arm.cc...
src/arm/macro-assembler-arm.cc:427: if (root->IsOddball() || root->IsMap() ||
Can you phrase this test as checking against a black-list rather than whitelist?
i.e. only do the ldr on roots where this won't work, and everything else uses
movw/movt? This will make sure that roots added in the future will also benefit
without having to add them them to this whitelist.

[danno, 2012-11-07 21:51:35]

Thanks for the patch.

LGTM, I will land this after I verify there is no performance regression.

http://codereview.chromium.org/11307012/diff/3001/src/heap.h
File src/heap.h (right):

http://codereview.chromium.org/11307012/diff/3001/src/heap.h#newcode1455
src/heap.h:1455: // they are in new space.
I don't think this comment is correct. The comment about being in new space
isn't accurate, and this patch doesn't check for it. I'll adjust before landing.