[GVN] Introduce test for PR125258 (NFC)

Author: antoniofrighetto

llvm/test/Transforms/GVN/does-clobber-errno.ll

@@ -0,0 +1,27 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=gvn -S < %s | FileCheck %s
+
+; FIXME: This is a miscompilation.
+define noundef i32 @test_malloc_clobbering_errno() {
+; CHECK-LABEL: define noundef i32 @test_malloc_clobbering_errno() {
+; CHECK-NEXT:    [[TMP1:%.*]] = alloca ptr, align 8
+; CHECK-NEXT:    [[TMP2:%.*]] = call ptr @__errno_location()
+; CHECK-NEXT:    store i32 0, ptr [[TMP2]], align 4
+; CHECK-NEXT:    [[TMP3:%.*]] = call noalias ptr @malloc(i64 1844674407370955161)
+; CHECK-NEXT:    store volatile ptr [[TMP3]], ptr [[TMP1]], align 8
+; CHECK-NEXT:    ret i32 0
+;
+  %1 = alloca ptr, align 8
+  %2 = call ptr @__errno_location()
+  store i32 0, ptr %2, align 4
+  %3 = call noalias ptr @malloc(i64 1844674407370955161)
+  store volatile ptr %3, ptr %1, align 8
+  %4 = load i32, ptr %2, align 4
+  ret i32 %4
+}
+
+declare ptr @__errno_location() #1
+declare noalias ptr @malloc(i64) #2
+
+attributes #1 = { mustprogress nofree nosync nounwind willreturn memory(none) }
+attributes #2 = { mustprogress nofree nounwind willreturn memory(inaccessiblemem: readwrite) }