Subzero, MIPS32: Intrinsic calls Ctlz and Cttz for i64

Subzero, MIPS32: Intrinsic calls Ctlz and Cttz for i64

Implements intrinsic calls llvm.ctlz and llvm.cttz for i64.
Also adds test cases for constant operands.

R=stichnot@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=6fd9c0e3f5b4c7e9e22dc982bbebbb5a891b35e9

[obucinac, 2016-09-23 16:21:27]

Description was changed from

==========
Subzero, MIPS32: Intrinsic call Ctlz for i64

Implements intrinsic call llvm.ctlz for i64.
Test for i32 constants added.
==========

to

==========
Subzero, MIPS32: Intrinsic call Ctlz for i64

Implements intrinsic call llvm.ctlz for i64.
Test for i32 constants added.
==========

[obucinac, 2016-09-23 16:21:27]

obucinac@gmail.com changed reviewers:
+ eholk@chromium.org, jaydeep.patil@imgtec.com, jpp@chromium.org,
kschimpf@google.com, sagar.thakur@imgtec.com, stichnot@chromium.org

[obucinac, 2016-09-23 16:24:22]

This is partially done (encoding check is missing),
and not suitable for commit at the moment.

Again, it is the same problem. Some instructions are
dead code eliminated in O2. And by everything I know,
these FakeUse's between clz and conditional move should
keep them alive, but I am getting liveness errors, and
cant find the right way to keep proper output.

[Jim Stichnoth, 2016-09-23 19:04:33]

On 2016/09/23 16:24:22, obucinac wrote:
> This is partially done (encoding check is missing),
> and not suitable for commit at the moment.
> 
> Again, it is the same problem. Some instructions are
> dead code eliminated in O2. And by everything I know,
> these FakeUse's between clz and conditional move should
> keep them alive, but I am getting liveness errors, and
> cant find the right way to keep proper output.

I think the very recent change to the movn implementation should fix the
liveness problem, specifically the change such that makes its dest also be one
of its sources.

You shouldn't need the FakeUses.

If I patch this in against latest master, only the encoding_intrinsics.ll test
fails.

I'll wait to review this until that lit test is ready.

[Jim Stichnoth, 2016-09-23 19:44:25]

On 2016/09/23 16:24:22, obucinac wrote:
> Again, it is the same problem. Some instructions are
> dead code eliminated in O2. And by everything I know,
> these FakeUse's between clz and conditional move should
> keep them alive, but I am getting liveness errors, and
> cant find the right way to keep proper output.

I'm sure that by now, you must be getting really tired of seeing liveness
validation errors. :)

But if it's any consolation, it's far better that the errors get flagged early
during translation.  Otherwise, they could lead to code quality problems (a
variable doesn't get a register because its liveness gets extended all the way
back to the beginning of the function), or correctness problems (two variables
incorrectly share a register because their live ranges were inadvertently
shortened).  I believe the liveness validation checks have saved uncountable
hours of debugging runtime failures.

When there are liveness errors, be sure to run with --verbose=all because that
often tries to give some more insight into the reason for flagging the error.

[obucinac, 2016-09-25 19:48:16]

Description was changed from

==========
Subzero, MIPS32: Intrinsic call Ctlz for i64

Implements intrinsic call llvm.ctlz for i64.
Test for i32 constants added.
==========

to

==========
Subzero, MIPS32: Intrinsic calls Ctlz and Cttz for i64

Implements intrinsic calls llvm.ctlz and llvm.cttz for i64.
Also adds test cases for constant operands.
==========

[obucinac, 2016-09-26 18:46:42]

Ready for review

[Jim Stichnoth, 2016-09-27 03:58:07]

lgtm

https://codereview.chromium.org/2364093002/diff/60001/tests_lit/assembler/mip...
File tests_lit/assembler/mips32/encoding_intrinsics.ll (right):

https://codereview.chromium.org/2364093002/diff/60001/tests_lit/assembler/mip...
tests_lit/assembler/mips32/encoding_intrinsics.ll:43: ; DIS-LABEL: {{.*}}
<encCtlz32>:
In the future, these patterns could be simplified by removing leading or
trailing "{{.*}}".

[Jim Stichnoth, 2016-09-27 03:58:19]

Description was changed from

==========
Subzero, MIPS32: Intrinsic calls Ctlz and Cttz for i64

Implements intrinsic calls llvm.ctlz and llvm.cttz for i64.
Also adds test cases for constant operands.
==========

to

==========
Subzero, MIPS32: Intrinsic calls Ctlz and Cttz for i64

Implements intrinsic calls llvm.ctlz and llvm.cttz for i64.
Also adds test cases for constant operands.

R=stichnot@chromium.org

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

[Jim Stichnoth, 2016-09-27 03:58:20]

Committed patchset #4 (id:60001) manually as
6fd9c0e3f5b4c7e9e22dc982bbebbb5a891b35e9 (presubmit successful).