[llvm] [ConstraintElim] Decompose sext-like insts for signed predicates (PR #82344)

[Florian Hahn via llvm-commits]

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@@ -601,6 +601,123 @@ else:
   ret i32 -1
 }
 
+define i64 @pr82271(i32 %a, i32 %b){
+; CHECK-LABEL: define i64 @pr82271
+; CHECK-SAME: (i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[A]], [[B]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK:       then:
+; CHECK-NEXT:    [[SA:%.*]] = sext i32 [[A]] to i64
+; CHECK-NEXT:    [[SB:%.*]] = sext i32 [[B]] to i64
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[SA]], 1
+; CHECK-NEXT:    ret i64 [[SB]]
+; CHECK:       else:
+; CHECK-NEXT:    ret i64 0
+;
+entry:
+  %cmp = icmp slt i32 %a, %b
+  br i1 %cmp, label %then, label %else
+
+then:
+  %sa = sext i32 %a to i64
+  %sb = sext i32 %b to i64
+  %add = add nsw i64 %sa, 1
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fhahn wrote:

Could you also add tests that check SExt/NNEgZExt support without min/max, e.g. by having a compare of the extended values?

https://github.com/llvm/llvm-project/pull/82344