1 files changed, 7 insertions, 1 deletions
diff --git a/llvm/lib/CodeGen/RegisterCoalescer.cpp b/llvm/lib/CodeGen/RegisterCoalescer.cpp
index 1803ea2b924..7b3a5d5c5ff 100644
--- a/llvm/lib/CodeGen/RegisterCoalescer.cpp
+++ b/llvm/lib/CodeGen/RegisterCoalescer.cpp
@@ -2666,11 +2666,17 @@ void JoinVals::pruneSubRegValues(LiveInterval &LI, LaneBitmask &ShrinkMask) {
   // Look for values being erased.
   bool DidPrune = false;
   for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
-    if (Vals[i].Resolution != CR_Erase)
+    // We should trigger in all cases in which eraseInstrs() does something.
+    // match what eraseInstrs() is doing, print a message so
+    if (Vals[i].Resolution != CR_Erase &&
+        (Vals[i].Resolution != CR_Keep || !Vals[i].ErasableImplicitDef ||
+         !Vals[i].Pruned))
       continue;
 
     // Check subranges at the point where the copy will be removed.
     SlotIndex Def = LR.getValNumInfo(i)->def;
+    // Print message so mismatches with eraseInstrs() can be diagnosed.
+    DEBUG(dbgs() << "\t\tExpecting instruction removal at " << Def << '\n');
     for (LiveInterval::SubRange &S : LI.subranges()) {
       LiveQueryResult Q = S.Query(Def);