RegisterCoalescer: Improve previous fix for wrong def after.

The previous fix in r225503 was needlessly complicated. The problem goes
away as well if the arguments to MergeValueNumberInto are supplied in the
correct order.
This was previously missed because the existing code already had the
wrong order but an additional later Merge was hiding the bug for the
main liverange VNI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229424 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 5cc11ae0309d25decc4c75e74a8b28c458088567..65b0e5026f095a8c4f71f4645bec1771149bf333 100644 (file)
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -738,15 +738,14 @@ bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
       continue;
     DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
     assert(DVNI->def == DefIdx);
-    BValNo = IntB.MergeValueNumberInto(BValNo, DVNI);
+    BValNo = IntB.MergeValueNumberInto(DVNI, BValNo);
     for (LiveInterval::SubRange &S : IntB.subranges()) {
       VNInfo *SubDVNI = S.getVNInfoAt(DefIdx);
       if (!SubDVNI)
         continue;
       VNInfo *SubBValNo = S.getVNInfoAt(CopyIdx);
       assert(SubBValNo->def == CopyIdx);
-      VNInfo *Merged = S.MergeValueNumberInto(SubBValNo, SubDVNI);
-      Merged->def = CopyIdx;
+      S.MergeValueNumberInto(SubDVNI, SubBValNo);
     }
 
     ErasedInstrs.insert(UseMI);