[TBAA] Tests for invalid tbaa.struct metadata (#86167)

These tests show invalid tbaa.struct metadata that is currently accepted
in preparation for a change to the IR Verifier that will then reject it.

PR: #86167

llvm/test/Verifier/tbaa-struct.ll

@@ -0,0 +1,40 @@
+; RUN: llvm-as < %s 2>&1
+
+; FIXME: The verifer should reject the invalid !tbaa.struct nodes below.
+
+define void @test_overlapping_regions(ptr %a1) {
+  %ld = load i8, ptr %a1, align 1, !tbaa.struct !0
+  ret void
+}
+
+define void @test_size_not_integer(ptr %a1) {
+  store i8 1, ptr %a1, align 1, !tbaa.struct !5
+  ret void
+}
+
+define void @test_offset_not_integer(ptr %a1, ptr %a2) {
+  tail call void @llvm.memcpy.p0.p0.i64(ptr align 8 %a1, ptr align 8 %a2, i64 16, i1 false), !tbaa.struct !6
+  ret void
+}
+
+define void @test_tbaa_missing(ptr %a1, ptr %a2) {
+  tail call void @llvm.memcpy.p0.p0.i64(ptr align 8 %a1, ptr align 8 %a2, i64 16, i1 false), !tbaa.struct !7
+  ret void
+}
+
+define void @test_tbaa_invalid(ptr %a1) {
+  store i8 1, ptr %a1, align 1, !tbaa.struct !8
+  ret void
+}
+
+declare void @llvm.memcpy.p0.p0.i64(ptr nocapture, ptr nocapture, i64, i1) nounwind
+
+!0 = !{i64 0, i64 4, !1, i64 1, i64 4, !1}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"int", !3, i64 0}
+!3 = !{!"omnipotent char", !4, i64 0}
+!4 = !{!"Simple C++ TBAA"}
+!5 = !{i64 0, !2, !1}
+!6 = !{!2, i64 0, !1}
+!7 = !{i64 0, i64 4, null}
+!8 = !{i64 0, i64 4, !2}