Imported Upstream version 5.18.0.246

Former-commit-id: 0c7ce5b1a7851e13f22acfd379b7f9fb304e4833

external/llvm/test/Transforms/DeadStoreElimination/invariant.start.ll

@@ -0,0 +1,34 @@
+; Test to make sure llvm.invariant.start calls are not treated as clobbers.
+; RUN: opt < %s -basicaa -dse -S | FileCheck %s
+
+declare {}* @llvm.invariant.start.p0i8(i64, i8* nocapture) nounwind readonly
+
+; We cannot remove the store 1 to %p.
+; FIXME: By the semantics of invariant.start, the store 3 to p is unreachable.
+define void @test(i8 *%p) {
+  store i8 1, i8* %p, align 4
+  %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %p)
+  store i8 3, i8* %p, align 4
+  ret void
+; CHECK-LABEL: @test(
+; CHECK-NEXT: store i8 1, i8* %p, align 4
+; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %p)
+; CHECK-NEXT: store i8 3, i8* %p, align 4
+; CHECK-NEXT: ret void
+}
+
+; FIXME: We should be able to remove the first store to p, even though p and q
+; may alias.
+define void @test2(i8* %p, i8* %q) {
+  store i8 1, i8* %p, align 4
+  store i8 2, i8* %q, align 4
+  %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %q)
+  store i8 3, i8* %p, align 4
+  ret void
+; CHECK-LABEL: @test2(
+; CHECK-NEXT: store i8 1, i8* %p, align 4
+; CHECK-NEXT: store i8 2, i8* %q, align 4
+; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %q)
+; CHECK-NEXT: store i8 3, i8* %p, align 4
+; CHECK-NEXT: ret void
+}