[llvm] [DA] Check monotonicity for subscripts (PR #154527)

[Ryotaro Kasuga via llvm-commits]

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@@ -685,11 +685,11 @@ exit:
 define void @coeff_positive(ptr %a, i32 %k) {
 ; CHECK-LABEL: 'coeff_positive'
 ; CHECK-NEXT:  Src: store i8 42, ptr %idx.0, align 1 --> Dst: store i8 42, ptr %idx.0, align 1
-; CHECK-NEXT:    da analyze - none!
+; CHECK-NEXT:    da analyze - confused!
 ; CHECK-NEXT:  Src: store i8 42, ptr %idx.0, align 1 --> Dst: store i8 42, ptr %idx.1, align 1
-; CHECK-NEXT:    da analyze - output [*|<]!
+; CHECK-NEXT:    da analyze - confused!
 ; CHECK-NEXT:  Src: store i8 42, ptr %idx.1, align 1 --> Dst: store i8 42, ptr %idx.1, align 1
-; CHECK-NEXT:    da analyze - none!
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kasuga-fj wrote:

Regarding this case, I think the original results are also correct. But to reason correctly, we need to infer that `%k` is non-zero, which seems to require a fair amount of effort.


https://github.com/llvm/llvm-project/pull/154527