Support/MemoryBuffer: Replace all uses of std::string *ErrMsg with error_code &ec. And fix clients.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121379 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AsmParser/Parser.cpp b/lib/AsmParser/Parser.cpp
index e7cef9b..a613a83 100644
--- a/lib/AsmParser/Parser.cpp
+++ b/lib/AsmParser/Parser.cpp
@@ -18,6 +18,7 @@
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/system_error.h"
 #include <cstring>
 using namespace llvm;
 
@@ -41,11 +42,11 @@
 
 Module *llvm::ParseAssemblyFile(const std::string &Filename, SMDiagnostic &Err,
                                 LLVMContext &Context) {
-  std::string ErrorStr;
-  MemoryBuffer *F = MemoryBuffer::getFileOrSTDIN(Filename.c_str(), &ErrorStr);
+  error_code ec;
+  MemoryBuffer *F = MemoryBuffer::getFileOrSTDIN(Filename.c_str(), ec);
   if (F == 0) {
     Err = SMDiagnostic(Filename,
-                       "Could not open input file: " + ErrorStr);
+                       "Could not open input file: " + ec.message());
     return 0;
   }