MIPS: Add support for arch. revision 6 to mips32 port.

MIPS: Add support for arch. revision 6 to mips32 port.

Additional summary:
 - Introduce fp64 fpu mode into mips32 port required for r6.
 - Implement runtime detections for fpu mode and arch. revision to preserve
   compatibility with previous architecture revisions.

TEST=
BUG=
R=jkummerow@chromium.org, paul.lind@imgtec.com

Committed: https://code.google.com/p/v8/source/detail?r=23028

[paul.l..., 2014-08-08 19:43:21]

LGTM for the MIPS part.  (Some very small issues found that you could fix when
landing.)
But we do still need a v8 team review for the arch-indep changes.

https://codereview.chromium.org/453043002/diff/1/src/mips/lithium-mips.cc
File src/mips/lithium-mips.cc (right):

https://codereview.chromium.org/453043002/diff/1/src/mips/lithium-mips.cc#new...
src/mips/lithium-mips.cc:1515: if (IsMipsArchVariant(kMips32r2)) {
This should be IsMipsArchVariant(kMips32r2) || IsMipsArchVariant(kMips32r6), as
we have madd.d on both variants.

https://codereview.chromium.org/453043002/diff/1/src/mips/lithium-mips.cc#new...
src/mips/lithium-mips.cc:1588: if (IsMipsArchVariant(kMips32r2)) {
as above, also allowed on mips32r6.

https://codereview.chromium.org/453043002/diff/1/src/mips/macro-assembler-mip...
File src/mips/macro-assembler-mips.cc (right):

https://codereview.chromium.org/453043002/diff/1/src/mips/macro-assembler-mip...
src/mips/macro-assembler-mips.cc:928: if (IsMipsArchVariant(kMips32r2)) {
Also allow on mips32r6, we have rotr, rotrv instructions there too.

https://codereview.chromium.org/453043002/diff/1/src/mips/macro-assembler-mip...
src/mips/macro-assembler-mips.cc:1150: if (IsMipsArchVariant(kMips32r2)) {
also mips32r6

https://codereview.chromium.org/453043002/diff/1/src/mips/macro-assembler-mip...
src/mips/macro-assembler-mips.cc:1174: if (IsMipsArchVariant(kMips32r2)) {
also mips32r6

[Jakob Kummerow, 2014-08-11 08:00:47]

non-MIPS changes LGTM with a few very minor formatting nits.

https://codereview.chromium.org/453043002/diff/1/build/toolchain.gypi
File build/toolchain.gypi (right):

https://codereview.chromium.org/453043002/diff/1/build/toolchain.gypi#newcode284
build/toolchain.gypi:284: 'cflags': ['-mfp64',],
nit: the comma before ']' isn't necessary (but I don't mind if it's there).

https://codereview.chromium.org/453043002/diff/1/build/toolchain.gypi#newcode336
build/toolchain.gypi:336: 'defines': ['_MIPS_ARCH_MIPS32R6','FPU_MODE_FP64',],
nit: space after comma please

https://codereview.chromium.org/453043002/diff/1/test/cctest/test-assembler-m...
File test/cctest/test-assembler-mips.cc (right):

https://codereview.chromium.org/453043002/diff/1/test/cctest/test-assembler-m...
test/cctest/test-assembler-mips.cc:822: if (!IsMipsArchVariant(kMips32r6)) {
nit: you could avoid the increased indentation below by inverting the condition:

if (IsMipsArchVariant(kMips32r6)) return;

[dusmil.imgtec, 2014-08-11 10:40:43]

Committed patchset #2 manually as 23028 (presubmit successful).