Saves callee-saved fpu registers on MIPS.

Saves callee-saved fpu registers on MIPS.

R=regis@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27063

[zra, 2013-08-30 00:08:49]

On entry to Dart code from C++ code.

We probably also need to do this for ARM. I'll look into it in a separate CL.

[regis, 2013-08-30 01:53:39]

LGTM

I am surprised we did not notice this earlier. We already had constants defined,
but did not use them:
kAbiFirstPreservedFpuReg and kAbiLastPreservedFpuReg.
Maybe you should remove them or use them instead of F20 and F31.

Yes, if you could do it for ARM later, that would be great.
Registers s16-s31 (d8-d15, q4-q7) must be preserved across subroutine calls.

Thanks,
Regis

https://codereview.chromium.org/23671003/diff/1/runtime/vm/stub_code_mips.cc
File runtime/vm/stub_code_mips.cc (right):

https://codereview.chromium.org/23671003/diff/1/runtime/vm/stub_code_mips.cc#...
runtime/vm/stub_code_mips.cc:916: (kAbiPreservedCpuRegCount +
kAbiPreservedFpuRegCount + 3) * kWordSize;
What are these 3 registers you save? 1 is the new context, but what are the
other 2? These must be top exit frame and old context. A comment would help.
Also a defined constant for 3 that you can reuse several times below would be
cleaner. This predated this cl...

https://codereview.chromium.org/23671003/diff/1/runtime/vm/stub_code_mips.cc#...
runtime/vm/stub_code_mips.cc:1024: Address(SP, (kAbiPreservedCpuRegCount + 3 + i
- F20) * kWordSize));
3 -> named constant defined above.

[zra, 2013-09-03 15:09:11]

I opted to go with keeping the constants and using them. They might come in
handy later on.

https://codereview.chromium.org/23671003/diff/1/runtime/vm/stub_code_mips.cc
File runtime/vm/stub_code_mips.cc (right):

https://codereview.chromium.org/23671003/diff/1/runtime/vm/stub_code_mips.cc#...
runtime/vm/stub_code_mips.cc:916: (kAbiPreservedCpuRegCount +
kAbiPreservedFpuRegCount + 3) * kWordSize;
On 2013/08/30 01:53:39, regis wrote:
> What are these 3 registers you save? 1 is the new context, but what are the
> other 2? These must be top exit frame and old context. A comment would help.
> Also a defined constant for 3 that you can reuse several times below would be
> cleaner. This predated this cl...

Done.

https://codereview.chromium.org/23671003/diff/1/runtime/vm/stub_code_mips.cc#...
runtime/vm/stub_code_mips.cc:1024: Address(SP, (kAbiPreservedCpuRegCount + 3 + i
- F20) * kWordSize));
On 2013/08/30 01:53:39, regis wrote:
> 3 -> named constant defined above.

Done.

[zra, 2013-09-03 15:17:26]

Committed patchset #2 manually as r27063 (presubmit successful).