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Commit ae597a77 authored by Jessica Paquette's avatar Jessica Paquette
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[AArch64][GlobalISel] Do not modify predicate when optimizing G_ICMP

This fixes a bug in `tryOptArithImmedIntegerCompare`.

It is unsafe to update the predicate on a MachineOperand when optimizing a
G_ICMP, because it may be used in more than one place.

For example, when we are optimizing G_SELECT, we allow compares which are used
in more than one G_SELECT. If we modify the G_ICMP, then we'll break one of
the G_SELECTs.

Since the compare is being produced to either

1) Select a G_ICMP
2) Fold a G_ICMP into an instruction when profitable

there's no reason to actually modify it. The change is local to the specific
compare.

Instead, pass a `CmpInst::Predicate` to `tryOptArithImmedIntegerCompare` which
can be modified by reference.

Differential Revision: https://reviews.llvm.org/D80585
parent 323d8504
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