[LiveRange] Reset the VNIs when splitting subranges

When splitting a subrange we end up with two different subranges covering
two different, non overlapping, lanes.
As part of this splitting the VNIs of the original live-range need
to be dispatched to the subranges according to which lanes they are
actually defining.

Prior to this patch we were assuming that all values were defining
all lanes. This was wrong as demonstrated by llvm.org/PR40835.

Differential Revision: https://reviews.llvm.org/D59731

llvm-svn: 357032

1 files changed, 26 insertions, 22 deletions

diff --git a/llvm/lib/CodeGen/RegisterCoalescer.cpp b/llvm/lib/CodeGen/RegisterCoalescer.cpp
index 4f1077787c9..40b7e8ba788 100644
--- a/llvm/lib/CodeGen/RegisterCoalescer.cpp
+++ b/llvm/lib/CodeGen/RegisterCoalescer.cpp
@@ -924,23 +924,25 @@ RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
     }
     SlotIndex AIdx = CopyIdx.getRegSlot(true);
     LaneBitmask MaskA;
+    const SlotIndexes &Indexes = *LIS->getSlotIndexes();
     for (LiveInterval::SubRange &SA : IntA.subranges()) {
       VNInfo *ASubValNo = SA.getVNInfoAt(AIdx);
       assert(ASubValNo != nullptr);
       MaskA |= SA.LaneMask;
 
-      IntB.refineSubRanges(Allocator, SA.LaneMask,
-          [&Allocator,&SA,CopyIdx,ASubValNo,&ShrinkB]
-            (LiveInterval::SubRange &SR) {
-        VNInfo *BSubValNo = SR.empty()
-          ? SR.getNextValue(CopyIdx, Allocator)
-          : SR.getVNInfoAt(CopyIdx);
-        assert(BSubValNo != nullptr);
-        auto P = addSegmentsWithValNo(SR, BSubValNo, SA, ASubValNo);
-        ShrinkB |= P.second;
-        if (P.first)
-          BSubValNo->def = ASubValNo->def;
-      });
+      IntB.refineSubRanges(
+          Allocator, SA.LaneMask,
+          [&Allocator, &SA, CopyIdx, ASubValNo,
+           &ShrinkB](LiveInterval::SubRange &SR) {
+            VNInfo *BSubValNo = SR.empty() ? SR.getNextValue(CopyIdx, Allocator)
+                                           : SR.getVNInfoAt(CopyIdx);
+            assert(BSubValNo != nullptr);
+            auto P = addSegmentsWithValNo(SR, BSubValNo, SA, ASubValNo);
+            ShrinkB |= P.second;
+            if (P.first)
+              BSubValNo->def = ASubValNo->def;
+          },
+          Indexes, *TRI);
     }
     // Go over all subranges of IntB that have not been covered by IntA,
     // and delete the segments starting at CopyIdx. This can happen if
@@ -3262,16 +3264,18 @@ void RegisterCoalescer::mergeSubRangeInto(LiveInterval &LI,
                                           LaneBitmask LaneMask,
                                           CoalescerPair &CP) {
   BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
-  LI.refineSubRanges(Allocator, LaneMask,
-      [this,&Allocator,&ToMerge,&CP](LiveInterval::SubRange &SR) {
-    if (SR.empty()) {
-      SR.assign(ToMerge, Allocator);
-    } else {
-      // joinSubRegRange() destroys the merged range, so we need a copy.
-      LiveRange RangeCopy(ToMerge, Allocator);
-      joinSubRegRanges(SR, RangeCopy, SR.LaneMask, CP);
-    }
-  });
+  LI.refineSubRanges(
+      Allocator, LaneMask,
+      [this, &Allocator, &ToMerge, &CP](LiveInterval::SubRange &SR) {
+        if (SR.empty()) {
+          SR.assign(ToMerge, Allocator);
+        } else {
+          // joinSubRegRange() destroys the merged range, so we need a copy.
+          LiveRange RangeCopy(ToMerge, Allocator);
+          joinSubRegRanges(SR, RangeCopy, SR.LaneMask, CP);
+        }
+      },
+      *LIS->getSlotIndexes(), *TRI);
 }
 
 bool RegisterCoalescer::isHighCostLiveInterval(LiveInterval &LI) {