From: Matthias Braun <matze@braunis.de>
Date: Mon, 16 Feb 2015 19:34:27 +0000 (+0000)
Subject: RegisterCoalescer: Improve previous fix for wrong def after.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6f750267066c1f724452dc7b20344097987eff21;p=oota-llvm.git

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 5cc11ae0309..65b0e5026f0 100644
--- 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);