[PhaseOrdering] Add test for #95152 (NFC)

This depends on multiple passes agreeing on the semantics of
writeonly, so add a PhaseOrdering test for it.

Author: nikic

llvm/test/Transforms/PhaseOrdering/pr95152.ll

@@ -0,0 +1,56 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes='default<O3>' < %s | FileCheck %s
+
+; Make sure that interaction of "writable" with various passes does not
+; result in the elimination of the store prior to @j().
+; FIXME: This is a miscompile.
+
+declare void @use(i64)
+
+define void @j(ptr %p) optnone noinline {
+; CHECK-LABEL: define void @j(
+; CHECK-SAME: ptr [[P:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:    [[I:%.*]] = load i64, ptr [[P]], align 4
+; CHECK-NEXT:    call void @use(i64 [[I]])
+; CHECK-NEXT:    ret void
+;
+  %i = load i64, ptr %p
+  call void @use(i64 %i)
+  ret void
+}
+
+define void @h(ptr %p) {
+; CHECK-LABEL: define void @h(
+; CHECK-SAME: ptr [[P:%.*]]) local_unnamed_addr {
+; CHECK-NEXT:    store i64 3, ptr [[P]], align 4
+; CHECK-NEXT:    tail call void @j(ptr nonnull [[P]])
+; CHECK-NEXT:    ret void
+;
+  store i64 3, ptr %p
+  call void @j(ptr %p)
+  ret void
+}
+
+define void @g(ptr dead_on_unwind noalias writable dereferenceable(8) align 8 %p) minsize {
+; CHECK-LABEL: define void @g(
+; CHECK-SAME: ptr dead_on_unwind noalias nocapture writable writeonly align 8 dereferenceable(8) [[P:%.*]]) local_unnamed_addr #[[ATTR1:[0-9]+]] {
+; CHECK-NEXT:    tail call void @h(ptr nonnull [[P]])
+; CHECK-NEXT:    ret void
+;
+  %a = alloca i64
+  call void @h(ptr %a)
+  call void @llvm.memcpy(ptr align 8 %p, ptr align 8 %a, i64 8, i1 false)
+  ret void
+}
+
+define void @f(ptr dead_on_unwind noalias %p) {
+; CHECK-LABEL: define void @f(
+; CHECK-SAME: ptr dead_on_unwind noalias [[P:%.*]]) local_unnamed_addr {
+; CHECK-NEXT:    tail call void @j(ptr nonnull writeonly [[P]])
+; CHECK-NEXT:    store i64 43, ptr [[P]], align 4
+; CHECK-NEXT:    ret void
+;
+  call void @g(ptr %p)
+  store i64 43, ptr %p
+  ret void
+}