Takashi Idobe 1ad91beba9 [CodeGen] relax kill copy hoist restriction for vreg to phys reg copies with folded loads (#190304) ...

Resolves: https://github.com/llvm/llvm-project/issues/62452

Currently, `TwoAddressInstructionPass` has a blanket rule against moving
kill copies, since many copies are better handled later by coalescing.
However, that rule is too strict when the kill is a virtual register to
physical register copy and the current two-address instruction has a
folded load. In that case, keeping the copy in place can force the pass
to break the folded rm form into a mov rm + op rr, even though the
physical register copy itself cannot be coalesced away in the usual
sense.

This fixes a missed optimization where a folded IMUL64rm was rewritten
into MOV64rm + IMUL64rr because a later $rax = COPY %src was kept in
place for mul.

2026-04-08 10:08:18 +08:00

77 KiB

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