[BranchFolding] Set correct mem refs

[flyingforyou]

Summary

We might merge MBBICommon and MBBI's MMOs.

[reames]

Wow, yeah. Oops on my part.

LGTM

p.s. Can you *please* add a test case that covers this? It would have caught my typo to start with.

[flyingforyou]

Update test case.

lib/CodeGen/BranchFolding.cpp

while (CommonTailLen--) {
     while ((MBBICommon != MBBIECommon) && MBBICommon->isDebugValue())
       ++MBBICommon;
 
     assert(MBBICommon != MBBIECommon &&
            "Reached BB end within common tail length!");
     assert(MBBICommon->isIdenticalTo(&*MBBI) && "Expected matching MIIs!");
 
     if (MBBICommon->mayLoad() || MBBICommon->mayStore())
-      MBBICommon->setMemRefs(MBBI->mergeMemRefsWith(*MBBI));
+      MBBICommon->setMemRefs(MBBICommon->mergeMemRefsWith(*MBBI));
 
     ++MBBI;
     ++MBBICommon;
   }
 }
 
 // See if any of the blocks in MergePotentials (which all have a common single
 // successor, or all have no successor) can be tail-merged.  If there is a