vendor/llvm/llvm-trunk-r307894

1 files changed, 28 insertions, 0 deletions

diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index ff9bca092dbe..a67d07b36474 100644
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -1227,6 +1227,34 @@ bool RegisterCoalescer::reMaterializeTrivialDef(const CoalescerPair &CP,
         SR->createDeadDef(DefIndex, Alloc);
       }
     }
+
+    // Make sure that the subrange for resultant undef is removed
+    // For example:
+    //   vreg1:sub1<def,read-undef> = LOAD CONSTANT 1
+    //   vreg2<def> = COPY vreg1
+    // ==>
+    //   vreg2:sub1<def, read-undef> = LOAD CONSTANT 1
+    //     ; Correct but need to remove the subrange for vreg2:sub0
+    //     ; as it is now undef
+    if (NewIdx != 0 && DstInt.hasSubRanges()) {
+      // The affected subregister segments can be removed.
+      SlotIndex CurrIdx = LIS->getInstructionIndex(NewMI);
+      LaneBitmask DstMask = TRI->getSubRegIndexLaneMask(NewIdx);
+      bool UpdatedSubRanges = false;
+      for (LiveInterval::SubRange &SR : DstInt.subranges()) {
+        if ((SR.LaneMask & DstMask).none()) {
+          DEBUG(dbgs() << "Removing undefined SubRange "
+                << PrintLaneMask(SR.LaneMask) << " : " << SR << "\n");
+          // VNI is in ValNo - remove any segments in this SubRange that have this ValNo
+          if (VNInfo *RmValNo = SR.getVNInfoAt(CurrIdx.getRegSlot())) {
+            SR.removeValNo(RmValNo);
+            UpdatedSubRanges = true;
+          }
+        }
+      }
+      if (UpdatedSubRanges)
+        DstInt.removeEmptySubRanges();
+    }
   } else if (NewMI.getOperand(0).getReg() != CopyDstReg) {
     // The New instruction may be defining a sub-register of what's actually
     // been asked for. If so it must implicitly define the whole thing.