Add static cast to unsigned char whenever a character classification function is called with a signed char argument, in order to avoid assertions in Windows Debug configuration.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175006 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 86949a7..f5fc66c 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -2038,7 +2038,7 @@
 /// a matching constraint like "4".
 bool TargetLowering::AsmOperandInfo::isMatchingInputConstraint() const {
   assert(!ConstraintCode.empty() && "No known constraint!");
-  return isdigit(ConstraintCode[0]);
+  return isdigit(static_cast<unsigned char>(ConstraintCode[0]));
 }
 
 /// getMatchedOperand - If this is an input matching constraint, this method