Subzero: Deterministically sort local var stack offsets.

Subzero: Deterministically sort local var stack offsets.

Currently, TargetLowering::sortVarsByAlignment() uses the variable's required alignment as the primary key, but then std::sort() breaks ties arbitrarily.  This can give different results across different STL implementations, for example when building against LLVM trunk versus building in the PNaCl environment.

The fix is to use Variable::Number as the secondary key.

BUG= none
R=kschimpf@google.com

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=53dae72a05ab4e1c2f241fd6027a7ad1050843bd

[Jim Stichnoth, 2016-08-31 21:03:40]

Description was changed from

==========
Subzero: Deterministically sort local var stack offsets.

BUG= none
==========

to

==========
Subzero: Deterministically sort local var stack offsets.

Currently, TargetLowering::sortVarsByAlignment() uses the variable's required
alignment as the primary key, but then std::sort() breaks ties arbitrarily. 
This can give different results across different STL implementations, for
example when building against LLVM trunk versus building in the PNaCl
environment.

The fix is to use the variable number as the secondary key.

BUG= none
==========

[Jim Stichnoth, 2016-08-31 21:04:47]

Description was changed from

==========
Subzero: Deterministically sort local var stack offsets.

Currently, TargetLowering::sortVarsByAlignment() uses the variable's required
alignment as the primary key, but then std::sort() breaks ties arbitrarily. 
This can give different results across different STL implementations, for
example when building against LLVM trunk versus building in the PNaCl
environment.

The fix is to use the variable number as the secondary key.

BUG= none
==========

to

==========
Subzero: Deterministically sort local var stack offsets.

Currently, TargetLowering::sortVarsByAlignment() uses the variable's required
alignment as the primary key, but then std::sort() breaks ties arbitrarily. 
This can give different results across different STL implementations, for
example when building against LLVM trunk versus building in the PNaCl
environment.

The fix is to use Variable::Number as the secondary key.

BUG= none
==========

[Jim Stichnoth, 2016-08-31 21:04:47]

stichnot@chromium.org changed reviewers:
+ eholk@chromium.org, jpp@chromium.org, kschimpf@google.com

[Karl, 2016-08-31 21:12:37]

lgtm

[Jim Stichnoth, 2016-08-31 22:32:34]

Description was changed from

==========
Subzero: Deterministically sort local var stack offsets.

Currently, TargetLowering::sortVarsByAlignment() uses the variable's required
alignment as the primary key, but then std::sort() breaks ties arbitrarily. 
This can give different results across different STL implementations, for
example when building against LLVM trunk versus building in the PNaCl
environment.

The fix is to use Variable::Number as the secondary key.

BUG= none
==========

to

==========
Subzero: Deterministically sort local var stack offsets.

Currently, TargetLowering::sortVarsByAlignment() uses the variable's required
alignment as the primary key, but then std::sort() breaks ties arbitrarily. 
This can give different results across different STL implementations, for
example when building against LLVM trunk versus building in the PNaCl
environment.

The fix is to use Variable::Number as the secondary key.

BUG= none
R=kschimpf@google.com

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

[Jim Stichnoth, 2016-08-31 22:32:36]

Committed patchset #1 (id:1) manually as
53dae72a05ab4e1c2f241fd6027a7ad1050843bd (presubmit successful).