[llvm] [InstCombine] Fix UB in align-assume check (PR #201985)

[Sudharsan Veeravalli via llvm-commits]

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@@ -257,6 +270,16 @@ define ptr @assume_align_1(ptr %p) {
   ret ptr %p
 }
 
+define ptr @redundant_assume_align_null() {
+; CHECK-LABEL: @redundant_assume_align_null(
+; CHECK-NEXT:    call void @foo(ptr null)
+; CHECK-NEXT:    ret ptr null
+;
+  call void @llvm.assume(i1 true) [ "align"(ptr null, i64 8) ]
+  call void @foo(ptr null)
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svs-quic wrote:


https://godbolt.org/z/57bffd44G shows that we produce the assume even without the call. Removing this we well.

https://github.com/llvm/llvm-project/pull/201985