[PATCH] Mark vastart_save_xmm_regs as changing EFLAGS

Andrew Trick atrick at apple.com
Mon Dec 16 22:12:08 PST 2013

On Dec 15, 2013, at 12:25 AM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:

> This patch marks vastart_save_xmm_regs as changing EFLAGS.
> The vastart_save_xmm_regs pseudo-instruction expands to a test and a
> branch, so it modifies EFLAGS.  Mark it so, or else the scheduler might
> place it in the middle of another test+branch.
> This fixes a bug exposed by r192750, which turned on the MI Scheduler
> for X86.


For the record, the SD scheduler was the one reordering the TEST/VASTART. The change that caused it was moving to source order scheduling. As a result the TEST ended up in a totally different MI block.

Incidentally, MI Scheduler still fails to schedule the test+je together because test appears to have unmodelled side effects (unrelated issue).


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