Imported Upstream version 6.10.0.49

Former-commit-id: 1d6753294b2993e1fbf92de9366bb9544db4189b

external/llvm-project/compiler-rt/test/msan/tls_reuse.cc

@@ -0,0 +1,26 @@
+// RUN: %clangxx_msan -O0 %s -o %t && %run %t
+
+// Check that when TLS block is reused between threads, its shadow is cleaned.
+
+#include <pthread.h>
+#include <stdio.h>
+
+int __thread x;
+
+void *ThreadFn(void *) {
+  if (!x)
+    printf("zzz\n");
+  int y;
+  int * volatile p = &y;
+  x = *p;
+  return 0;
+}
+
+int main(void) {
+  pthread_t t;
+  for (int i = 0; i < 100; ++i) {
+    pthread_create(&t, 0, ThreadFn, 0);
+    pthread_join(t, 0);
+  }
+  return 0;
+}