disable this entirely: it is causing use of invalidated iterators and infinite looping.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42739 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86RegisterInfo.cpp

@@ -1505,6 +1505,8 @@ static
 void mergeSPUpdatesDown(MachineBasicBlock &MBB,
                         MachineBasicBlock::iterator &MBBI,
                         unsigned StackPtr, uint64_t *NumBytes = NULL) {
+  return;
+  
   if (MBBI == MBB.end()) return;
   
   MachineBasicBlock::iterator NI = next(MBBI);