Replace 2 ARM ldr instructions with one ldrd in the code generated...

Replace 2 ARM ldr instructions with one ldrd in the code generated
for a SubStringStub and StringCompareStub in the ARM backend.  This
is a commit of http://codereview.chromium.org/3341012 for Andreas
Anyuru.

Committed: http://code.google.com/p/v8/source/detail?r=5457

[Søren Thygesen Gjesse, 2010-09-15 10:09:06]

LGTM

http://codereview.chromium.org/3387003/diff/1/3
File src/arm/code-stubs-arm.cc (right):

http://codereview.chromium.org/3387003/diff/1/3#newcode4218
src/arm/code-stubs-arm.cc:4218: __ b(lt, &runtime);  // Fail if to > length.
Looks as if "to" is not live after here, maybe set it to no_reg at this point...

http://codereview.chromium.org/3387003/diff/1/3#newcode4242
src/arm/code-stubs-arm.cc:4242: Label make_two_character_string;
... and then "from" should be set to no_reg here (and before all other calls to
StringHelper functions which clobbers r7) ... maybe not.

http://codereview.chromium.org/3387003/diff/1/3#newcode4309
src/arm/code-stubs-arm.cc:4309: StringHelper::GenerateCopyCharactersLong(masm,
r1, r5, r2, r3, r4, r6, r7,
All arguments on a single (new line)?

[Erik Corry, 2010-09-15 10:22:41]

http://codereview.chromium.org/3387003/diff/1/3
File src/arm/code-stubs-arm.cc (right):

http://codereview.chromium.org/3387003/diff/1/3#newcode4218
src/arm/code-stubs-arm.cc:4218: __ b(lt, &runtime);  // Fail if to > length.
On 2010/09/15 10:09:07, Søren Gjesse wrote:
> Looks as if "to" is not live after here, maybe set it to no_reg at this
point...

Done.

http://codereview.chromium.org/3387003/diff/1/3#newcode4242
src/arm/code-stubs-arm.cc:4242: Label make_two_character_string;
On 2010/09/15 10:09:07, Søren Gjesse wrote:
> ... and then "from" should be set to no_reg here (and before all other calls
to
> StringHelper functions which clobbers r7) ... maybe not.

No, r7 with its original contents is used below here.

http://codereview.chromium.org/3387003/diff/1/3#newcode4309
src/arm/code-stubs-arm.cc:4309: StringHelper::GenerateCopyCharactersLong(masm,
r1, r5, r2, r3, r4, r6, r7,
On 2010/09/15 10:09:07, Søren Gjesse wrote:
> All arguments on a single (new line)?

Done.