Workaround an MSan false positive.

llvm-svn: 175156
diff --git a/llvm/lib/Support/Unix/Process.inc b/llvm/lib/Support/Unix/Process.inc
index 1335b78..9a4454f 100644
--- a/llvm/lib/Support/Unix/Process.inc
+++ b/llvm/lib/Support/Unix/Process.inc
@@ -224,6 +224,8 @@
 #if defined(HAVE_SYS_IOCTL_H) && defined(HAVE_TERMIOS_H)
   // Try to determine the width of the terminal.
   struct winsize ws;
+  // Zero-fill ws to avoid a false positive from MemorySanitizer.
+  memset(&ws, 0, sizeof(ws));
   if (ioctl(FileID, TIOCGWINSZ, &ws) == 0)
     Columns = ws.ws_col;
 #endif