[llvm] [DAG] Fold (umin (sub a b) a) -> (usubo a b); (select usubo.1 a usubo.0) (PR #161651)

[Matt Arsenault via llvm-commits]

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+; RUN: llc < %s -mtriple=aarch64 | FileCheck %s
+
+; GitHub issue #161036
+
+; Positive test : umin(sub(a,b),a) with scalar types should be folded
+define i64 @underflow_compare_fold(i64 %a, i64 %b) {
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arsenm wrote:

Misses the case where the min is commuted? 

https://github.com/llvm/llvm-project/pull/161651