[llvm] [GlobalIsel] Visit ICmp (PR #105991)

[Thorsten Schütt via llvm-commits]

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@@ -1884,6 +1881,28 @@ def cast_combines: GICombineGroup<[
   buildvector_of_truncate
 ]>;
 
+def visit_icmp : GICombineRule<
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tschuett wrote:

Combining compares is a good and hard sport. Maybe different rules apply.

CombinerHelper::visitICmp first tries to constant fold the compare, if that fails it tries to canonicalize the constant to right. It is hard to put that into two separate patterns, which are not wip_match_opcode G_ICMP.

I have no interest to ever add a visitMULH. Adding a visitFCmp is a different story.

https://github.com/llvm/llvm-project/pull/105991