Fix column checking for SourceManager::getLocation().

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74194 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 69b6be7..6640c61 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -943,7 +943,7 @@
     return SourceLocation();
   
   unsigned FilePos = Content->SourceLineCache[Line - 1];
-  const char *Buf = Content->getBuffer()->getBufferStart();
+  const char *Buf = Content->getBuffer()->getBufferStart() + FilePos;
   unsigned BufLength = Content->getBuffer()->getBufferEnd() - Buf;
   unsigned i = 0;