Use StringRef::substr instead of std::string::substr to avoid using a free'd
string temporary. This should fix PR6590.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98349 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index fc30b13..8c09eec 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -9837,7 +9837,8 @@
         AsmPieces[2] == "${0:w}" &&
         IA->getConstraintString().compare(0, 5, "=r,0,") == 0) {
       AsmPieces.clear();
-      SplitString(IA->getConstraintString().substr(5), AsmPieces, ",");
+      const std::string &Constraints = IA->getConstraintString();
+      SplitString(StringRef(Constraints).substr(5), AsmPieces, ",");
       std::sort(AsmPieces.begin(), AsmPieces.end());
       if (AsmPieces.size() == 4 &&
           AsmPieces[0] == "~{cc}" &&