Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

The problem was that the lowering sequence might lead to the rem result %ah being directly moved into an 8-bit register other than al/bl/cl/dl/ah/bh/ch/dh.  This is not encodable, and attempting to encode it leads to actually moving from %spl instead of %ah.

The machinery to handle this was already available - copy through a temporary with register class RCX86_IsAhRcvr.  So this was just a matter of hooking it up for srem/urem.

This CL also requires relaxing some checks in the register allocator for when the -reg-reserve option is used.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
R=jpp@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=2655d9627f11b0c97f10eacf1f730bf66e5db05b

[Jim Stichnoth, 2016-04-21 05:58:23]

Description was changed from

==========
Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
==========

to

==========
Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

The problem was that the lowering sequence might lead to the rem result %ah
being directly moved into an 8-bit register other than al/bl/cl/dl/ah/bh/ch/dh. 
This is not actually encodable, and attempting to encode it leads to actually
moving from %spl instead of %ah.

The machinery to handle this was already in place - copy through a temporary
with register class RCX86_IsAhRcvr.  So this was just a matter of hooking it up
for srem/urem.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
==========

[Jim Stichnoth, 2016-04-21 06:00:52]

Description was changed from

==========
Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

The problem was that the lowering sequence might lead to the rem result %ah
being directly moved into an 8-bit register other than al/bl/cl/dl/ah/bh/ch/dh. 
This is not actually encodable, and attempting to encode it leads to actually
moving from %spl instead of %ah.

The machinery to handle this was already in place - copy through a temporary
with register class RCX86_IsAhRcvr.  So this was just a matter of hooking it up
for srem/urem.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
==========

to

==========
Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

The problem was that the lowering sequence might lead to the rem result %ah
being directly moved into an 8-bit register other than al/bl/cl/dl/ah/bh/ch/dh. 
This is not encodable, and attempting to encode it leads to actually moving from
%spl instead of %ah.

The machinery to handle this was already available - copy through a temporary
with register class RCX86_IsAhRcvr.  So this was just a matter of hooking it up
for srem/urem.

This CL also requires relaxing some checks in the register allocator for when
the -reg-reserve option is used.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
==========

[Jim Stichnoth, 2016-04-21 06:00:52]

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

[John, 2016-04-21 12:23:36]

lgtm

[Jim Stichnoth, 2016-04-21 12:38:19]

Description was changed from

==========
Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

The problem was that the lowering sequence might lead to the rem result %ah
being directly moved into an 8-bit register other than al/bl/cl/dl/ah/bh/ch/dh. 
This is not encodable, and attempting to encode it leads to actually moving from
%spl instead of %ah.

The machinery to handle this was already available - copy through a temporary
with register class RCX86_IsAhRcvr.  So this was just a matter of hooking it up
for srem/urem.

This CL also requires relaxing some checks in the register allocator for when
the -reg-reserve option is used.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
==========

to

==========
Subzero: Fix srem.i8/urem.i8 lowering for x86-64.

The problem was that the lowering sequence might lead to the rem result %ah
being directly moved into an 8-bit register other than al/bl/cl/dl/ah/bh/ch/dh. 
This is not encodable, and attempting to encode it leads to actually moving from
%spl instead of %ah.

The machinery to handle this was already available - copy through a temporary
with register class RCX86_IsAhRcvr.  So this was just a matter of hooking it up
for srem/urem.

This CL also requires relaxing some checks in the register allocator for when
the -reg-reserve option is used.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4370
R=jpp@chromium.org

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

[Jim Stichnoth, 2016-04-21 12:38:20]

Committed patchset #1 (id:1) manually as
2655d9627f11b0c97f10eacf1f730bf66e5db05b (presubmit successful).