TableGen: Allow AddedComplexity values to be negative

This is useful for cases when stand-alone patterns are preferred to the
patterns included in the instruction definitions.  Instead of requiring
that stand-alone patterns set a larger AddedComplexity value, which
can be confusing to new developers, the allows us to reduce the
complexity of the included patterns to achieve the same result.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213521 91177308-0d34-0410-b5e6-96231b3b80d8

utils/TableGen/CodeGenDAGPatterns.cpp

@@ -771,7 +771,7 @@ static unsigned getPatternSize(const TreePatternNode *P,
 
 /// Compute the complexity metric for the input pattern.  This roughly
 /// corresponds to the number of nodes that are covered.
-unsigned PatternToMatch::
+int PatternToMatch::
 getPatternComplexity(const CodeGenDAGPatterns &CGP) const {
   return getPatternSize(getSrcPattern(), CGP) + getAddedComplexity();
 }