Make tail merging the default, except on powerPC. There was no prior art

for a target-dependent default with a command-line override; this way
should be generally usable.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37285 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/Passes.h

@@ -79,7 +79,7 @@ namespace llvm {
   /// optimizations to delete branches to branches, eliminate branches to
   /// successor blocks (creating fall throughs), and eliminating branches over
   /// branches.
-  FunctionPass *createBranchFoldingPass();
+  FunctionPass *createBranchFoldingPass(bool DefaultEnableTailMerge);
 
   /// IfConverter Pass - This pass performs machine code if conversion.
   FunctionPass *createIfConverterPass();