[llvm] [AtomicExpandPass] Match isIdempotentRMW with InstcombineRMW (PR #142277)

[Simon Pilgrim via llvm-commits]

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@@ -622,4 +622,365 @@ define void @or8_nouse_seq_cst(ptr %p) #0 {
   ret void
 }
 
+define void @atomic_umin_uint_max(ptr %addr) #0 {
+; CHECK-LABEL: @atomic_umin_uint_max(
+; CHECK-NEXT:    [[RES:%.*]] = atomicrmw or ptr [[ADDR:%.*]], i32 0 monotonic, align 4
+; CHECK-NEXT:    ret i32 [[RES]]
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RKSimon wrote:

where have these CHECK prefixes come from?

https://github.com/llvm/llvm-project/pull/142277