Since 6524a7a2b9, this would sometimes
not emit the or to exec at the beginning of the block, where it really
has to be. If there is an instruction that defines one of the source
operands, split the block and turn the si_end_cf into a terminator.
This avoids regressions when regalloc fast is switched to inserting
reloads at the beginning of the block, instead of spills at the end of
the block.
In a future change, this should always split the block.
PHIElimination/createPHISourceCopy inserts non-branch terminators
after the control flow pseudo if a successor phi reads a register
defined by the control flow pseudo. If this happens, we need to split
the expansion of the control flow pseudo to ensure all the branches
are after all of the other mask management instructions.
GlobalISel hit this in testscases that happened to be tail
duplicated. The original testcase still does not work, since the same
problem appears to be present in a later pass.
Matt Arsenault