[Subzero][MIPS] Implement conditional branches with 64-bit integer compares

[Subzero][MIPS] Implement conditional branches with 64-bit integer compares

R=stichnot@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=9309756d32e760188e111dec5672050637cd0eca

[sagar.thakur, 2016-09-29 11:01:59]

sagar.thakur@imgtec.com changed reviewers:
+ eholk@chromium.org, jpp@chromium.org, kschimpf@google.com,
srdjan.obucina@imgtec.com, stichnot@chromium.org

[Jim Stichnoth, 2016-09-29 13:52:20]

LGTM, though honestly I didn't deeply inspect all the lowering sequences or the
tests.

I will have much more confidence from the test_icmp cross test. :)

https://codereview.chromium.org/2384433002/diff/20001/tests_lit/llvm2ice_test...
File tests_lit/llvm2ice_tests/64bit.pnacl.ll (right):

https://codereview.chromium.org/2384433002/diff/20001/tests_lit/llvm2ice_test...
tests_lit/llvm2ice_tests/64bit.pnacl.ll:1309: ; MIPS32-OM1: sw [[T4]],[[MEM:.*]]
I am very impressed by the level of detail in these tests.  I would never have
the patience to write these. :)

One suggestion for the future.  Especially for Om1 tests, I would focus on the
"real" instructions like xor/bnez/sltiu that the register allocator will not
affect.  In contrast, loading a register from the stack and storing a register
onto the stack are instructions that might go away in the future if we made some
tweak to improve the Om1 register allocator (unlikely as that might be).  I
think this sw/lb sequence is not there in O2 because of the register allocator.

In other words, it may be more future-proof to avoid specifically testing the
output of a _mov() or a legalizeToReg() operation from the lowering sequence.

[Jim Stichnoth, 2016-09-29 13:52:32]

Description was changed from

==========
[Subzero][MIPS] Implement conditional branches with 64-bit integer compares
==========

to

==========
[Subzero][MIPS] Implement conditional branches with 64-bit integer compares

R=stichnot@chromium.org

Committed:
https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a...
==========

[Jim Stichnoth, 2016-09-29 13:52:34]

Committed patchset #2 (id:20001) manually as
9309756d32e760188e111dec5672050637cd0eca (presubmit successful).