[GVNHoist] Fix a signed/unsigned comparison warning that occurs in 32-bit builds with gcc.

std::distance returns ptrdiff_t which is signed. 64-bit builds don't notice because type promotion widens the unsigned first.

llvm-svn: 318354

Author: topperc

llvm/lib/Transforms/Scalar/GVNHoist.cpp

@@ -578,7 +578,7 @@ class GVNHoist {
 
   // Returns true when the values are flowing out to each edge.
   bool valueAnticipable(CHIArgs C, TerminatorInst *TI) const {
-    if (TI->getNumSuccessors() > std::distance(C.begin(), C.end()))
+    if (TI->getNumSuccessors() > (unsigned)std::distance(C.begin(), C.end()))
       return false; // Not enough args in this CHI.
 
     for (auto CHI : C) {