Imported Upstream version 6.10.0.49

Former-commit-id: 1d6753294b2993e1fbf92de9366bb9544db4189b

external/llvm-project/compiler-rt/test/tsan/tsan-vs-gvn.cc

@@ -0,0 +1,38 @@
+// RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_tsan -O2 %s -o %t && %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_tsan -O3 %s -o %t && %run %t 2>&1 | FileCheck %s
+//
+// Check that load widening is not tsan-hostile.
+#include <pthread.h>
+#include <stdio.h>
+#include <string.h>
+
+struct {
+  int i;
+  char c1, c2, c3, c4;
+} S;
+
+int G;
+
+void *Thread1(void *x) {
+  G = S.c1 + S.c3;
+  return NULL;
+}
+
+void *Thread2(void *x) {
+  S.c2 = 1;
+  return NULL;
+}
+
+int main() {
+  pthread_t t[2];
+  memset(&S, 123, sizeof(S));
+  pthread_create(&t[0], NULL, Thread1, NULL);
+  pthread_create(&t[1], NULL, Thread2, NULL);
+  pthread_join(t[0], NULL);
+  pthread_join(t[1], NULL);
+  fprintf(stderr, "PASS\n");
+}
+
+// CHECK-NOT: WARNING: ThreadSanitizer: data race
+// CHECK: PASS