ARM: Improve SeqStringSetChar implementation.

ARM: Improve SeqStringSetChar implementation.

TEST=/test/mjsunit/lithium/SeqStringSetChar.js
R=bmeurer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16707

[Benedikt Meurer, 2013-09-09 06:05:31]

https://codereview.chromium.org/23890007/diff/1/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

https://codereview.chromium.org/23890007/diff/1/src/arm/lithium-codegen-arm.c...
src/arm/lithium-codegen-arm.cc:1985: FieldMemOperand(string,
SeqString::kHeaderSize + constant_index));
Is that safe for arbitrary constant_index'es?

[vincent.belliard.fr, 2013-09-09 08:29:55]

https://codereview.chromium.org/23890007/diff/1/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

https://codereview.chromium.org/23890007/diff/1/src/arm/lithium-codegen-arm.c...
src/arm/lithium-codegen-arm.cc:1985: FieldMemOperand(string,
SeqString::kHeaderSize + constant_index));
On 2013/09/09 06:05:31, Benedikt Meurer wrote:
> Is that safe for arbitrary constant_index'es?
As long as you don't use ip, it's safe (and you should not use ip outside of
assembler or macroassembler).
When the constant can be encoded within the instruction, it only generates a
strb. If not, it will first load the constant in ip and then do the strb.

[Benedikt Meurer, 2013-09-13 09:12:34]

LGTM.

[Benedikt Meurer, 2013-09-13 09:14:08]

Committed patchset #1 manually as r16707.