Replace a temporary std::string with SmallString.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97259 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp
index 9253b01..eb046d0 100644
--- a/lib/Support/MemoryBuffer.cpp
+++ b/lib/Support/MemoryBuffer.cpp
@@ -174,7 +174,8 @@
 #ifdef O_BINARY
   OpenFlags |= O_BINARY;  // Open input file in binary mode on win32.
 #endif
-  int FD = ::open(Filename.str().c_str(), O_RDONLY|OpenFlags);
+  SmallString<256> PathBuf(Filename.begin(), Filename.end());
+  int FD = ::open(PathBuf.c_str(), O_RDONLY|OpenFlags);
   if (FD == -1) {
     if (ErrStr) *ErrStr = strerror(errno);
     return 0;