Fix MIPS assembler test.

Fix MIPS assembler test.

R=regis@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42746

[zra, 2015-01-09 16:10:02]

zra@google.com changed reviewers:
+ regis@google.com

[regis, 2015-01-09 17:16:02]

LGTM (kind of) with comments.

https://codereview.chromium.org/791953003/diff/1/runtime/vm/assembler_mips_te...
File runtime/vm/assembler_mips_test.cc (right):

https://codereview.chromium.org/791953003/diff/1/runtime/vm/assembler_mips_te...
runtime/vm/assembler_mips_test.cc:1643: __ AddImmediate(SP, -8 * kWordSize);
Why 8*kWordSize?
A double is 2*kWordSize, alignment requires an additional kWordSize, so
3*kWordSize should do.

https://codereview.chromium.org/791953003/diff/1/runtime/vm/assembler_mips_te...
runtime/vm/assembler_mips_test.cc:1646: __ AddImmediate(T0, T0, 2 * kWordSize);
This may work with 8*kWordSize above, but this is not necessary, and definitely
wrong with 3*kWordSize.

https://codereview.chromium.org/791953003/diff/1/runtime/vm/assembler_mips_te...
runtime/vm/assembler_mips_test.cc:1650: __ AddImmediate(SP, 8 * kWordSize);
3*kWordSize?

It is only a test and efficiency is not important, but I find it hard to read. I
would have worked with SP directly:

mov T0, SP  // Save SP
addiu SP, -3*kWordSize
andi SP, 7
... use SP as base for sdc1 and ldc1 ...
mov SP, T0

[zra, 2015-01-09 17:49:28]

Thanks!

https://codereview.chromium.org/791953003/diff/1/runtime/vm/assembler_mips_te...
File runtime/vm/assembler_mips_test.cc (right):

https://codereview.chromium.org/791953003/diff/1/runtime/vm/assembler_mips_te...
runtime/vm/assembler_mips_test.cc:1650: __ AddImmediate(SP, 8 * kWordSize);
On 2015/01/09 17:16:02, regis wrote:
> 3*kWordSize?
> 
> It is only a test and efficiency is not important, but I find it hard to read.
I
> would have worked with SP directly:
> 
> mov T0, SP  // Save SP
> addiu SP, -3*kWordSize
> andi SP, 7
> ... use SP as base for sdc1 and ldc1 ...
> mov SP, T0

Changed to something like this.

[regis, 2015-01-09 17:55:23]

LGTM

[zra, 2015-01-09 17:59:15]

Committed patchset #3 (id:40001) manually as r42746 (presubmit successful).