fix a -Wbool-conversions warning from clang.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105943 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/CBackend/CBackend.cpp b/lib/Target/CBackend/CBackend.cpp
index 55b8aaa..fa145b2 100644
--- a/lib/Target/CBackend/CBackend.cpp
+++ b/lib/Target/CBackend/CBackend.cpp
@@ -264,7 +264,7 @@
     //
     static const AllocaInst *isDirectAlloca(const Value *V) {
       const AllocaInst *AI = dyn_cast<AllocaInst>(V);
-      if (!AI) return false;
+      if (!AI) return 0;
       if (AI->isArrayAllocation())
         return 0;   // FIXME: we can also inline fixed size array allocas!
       if (AI->getParent() != &AI->getParent()->getParent()->getEntryBlock())