1 files changed, 46 insertions, 39 deletions

diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp
index 53141b54c9..ef5650c861 100644
--- a/lib/CodeGen/SplitKit.cpp
+++ b/lib/CodeGen/SplitKit.cpp
@@ -145,7 +145,7 @@ void SplitAnalysis::analyzeUses() {
 /// where CurLI is live.
 bool SplitAnalysis::calcLiveBlockInfo() {
   ThroughBlocks.resize(MF.getNumBlockIDs());
-  NumThroughBlocks = 0;
+  NumThroughBlocks = NumGapBlocks = 0;
   if (CurLI->empty())
     return true;
 
@@ -164,55 +164,62 @@ bool SplitAnalysis::calcLiveBlockInfo() {
     SlotIndex Start, Stop;
     tie(Start, Stop) = LIS.getSlotIndexes()->getMBBRange(BI.MBB);
 
-    // LVI is the first live segment overlapping MBB.
-    BI.LiveIn = LVI->start <= Start;
-    if (!BI.LiveIn)
-      BI.Def = LVI->start;
-
-    // Find the first and last uses in the block.
-    bool Uses = UseI != UseE && *UseI < Stop;
-    if (Uses) {
+    // If the block contains no uses, the range must be live through. At one
+    // point, SimpleRegisterCoalescing could create dangling ranges that ended
+    // mid-block.
+    if (UseI == UseE || *UseI >= Stop) {
+      ++NumThroughBlocks;
+      ThroughBlocks.set(BI.MBB->getNumber());
+      // The range shouldn't end mid-block if there are no uses. This shouldn't
+      // happen.
+      if (LVI->end < Stop)
+        return false;
+    } else {
+      // This block has uses. Find the first and last uses in the block.
       BI.FirstUse = *UseI;
       assert(BI.FirstUse >= Start);
       do ++UseI;
       while (UseI != UseE && *UseI < Stop);
       BI.LastUse = UseI[-1];
       assert(BI.LastUse < Stop);
-    }
 
-    // Look for gaps in the live range.
-    bool hasGap = false;
-    BI.LiveOut = true;
-    while (LVI->end < Stop) {
-      SlotIndex LastStop = LVI->end;
-      if (++LVI == LVE || LVI->start >= Stop) {
-        BI.Kill = LastStop;
-        BI.LiveOut = false;
-        break;
-      }
-      if (LastStop < LVI->start) {
-        hasGap = true;
-        BI.Kill = LastStop;
-        BI.Def = LVI->start;
+      // LVI is the first live segment overlapping MBB.
+      BI.LiveIn = LVI->start <= Start;
+
+      // Look for gaps in the live range.
+      BI.LiveOut = true;
+      while (LVI->end < Stop) {
+        SlotIndex LastStop = LVI->end;
+        if (++LVI == LVE || LVI->start >= Stop) {
+          BI.LiveOut = false;
+          break;
+        }
+        if (LastStop < LVI->start) {
+          // There is a gap in the live range. Create duplicate entries for the
+          // live-in snippet and the live-out snippet.
+          ++NumGapBlocks;
+
+          // Push the Live-in part.
+          BI.LiveThrough = false;
+          BI.LiveOut = false;
+          UseBlocks.push_back(BI);
+          UseBlocks.back().LastUse = LastStop;
+
+          // Set up BI for the live-out part.
+          BI.LiveIn = false;
+          BI.LiveOut = true;
+          BI.FirstUse = LVI->start;
+        }
       }
-    }
 
-    // Don't set LiveThrough when the block has a gap.
-    BI.LiveThrough = !hasGap && BI.LiveIn && BI.LiveOut;
-    if (Uses)
+      // Don't set LiveThrough when the block has a gap.
+      BI.LiveThrough = BI.LiveIn && BI.LiveOut;
       UseBlocks.push_back(BI);
-    else {
-      ++NumThroughBlocks;
-      ThroughBlocks.set(BI.MBB->getNumber());
-    }
-    // FIXME: This should never happen. The live range stops or starts without a
-    // corresponding use. An earlier pass did something wrong.
-    if (!BI.LiveThrough && !Uses)
-      return false;
 
-    // LVI is now at LVE or LVI->end >= Stop.
-    if (LVI == LVE)
-      break;
+      // LVI is now at LVE or LVI->end >= Stop.
+      if (LVI == LVE)
+        break;
+    }
 
     // Live segment ends exactly at Stop. Move to the next segment.
     if (LVI->end == Stop && ++LVI == LVE)