Subzero: Force ebp-based frame when an alloca has a large alignment.

Subzero: Force ebp-based frame when an alloca has a large alignment.

If the alloca alignment exceeds the known ABI stack alignment, the lowering sequence adds an "and esp, xxx" instruction.  In this case, the esp adjustment is no longer statically known, so we must force an ebp-based frame.

BUG= none
R=sehr@google.com

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=8686139f458786afd21f59aedbb2debabcdff803

[Jim Stichnoth, 2015-10-31 14:42:24]

Description was changed from

==========
Subzero: Force ebp-based frame when an alloca has a large alignment.

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

to

==========
Subzero: Force ebp-based frame when an alloca has a large alignment.

If the alloca alignment exceeds the known ABI stack alignment, the lowering
sequence adds an "and esp, xxx" instruction.  In this case, the esp adjustment
is no longer statically known, so we must force an ebp-based frame.

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

[Jim Stichnoth, 2015-10-31 14:42:24]

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

[Jim Stichnoth, 2015-10-31 14:44:14]

As might be expected, spec2k was unaffected by this bug.

[sehr (please use chromium), 2015-10-31 18:16:13]

LGTM, and thanks!

[Jim Stichnoth, 2015-10-31 19:55:32]

Committed patchset #1 (id:1) manually as
8686139f458786afd21f59aedbb2debabcdff803 (presubmit successful).