Fix the updating of LiveIntervals after splitting a critical edge. PHI operand

live ranges should always be extended, and the only successor that should be
considered for extension of other ranges is the target of the split edge.

llvm-svn: 174935

1 files changed, 3 insertions, 12 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 7351302cc32..71d59f0b4b3 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -796,8 +796,8 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
           MachineOperand &MO = I->getOperand(ni);
           unsigned Reg = MO.getReg();
           PHISrcRegs.insert(Reg);
-          if (MO.isUndef() || !isLastMBB)
-            break;
+          if (MO.isUndef())
+            continue;
 
           LiveInterval &LI = LIS->getInterval(Reg);
           VNInfo *VNI = LI.getVNInfoAt(PrevIndex);
@@ -817,16 +817,7 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
       if (!LI.liveAt(PrevIndex))
         continue;
 
-      bool isLiveOut = false;
-      for (MachineBasicBlock::succ_iterator SI = succ_begin(),
-           SE = succ_end(); SI != SE; ++SI) {
-        MachineBasicBlock *SuccMBB = *SI == NMBB ? Succ : *SI;
-        if (LI.liveAt(LIS->getMBBStartIdx(SuccMBB))) {
-          isLiveOut = true;
-          break;
-        }
-      }
-
+      bool isLiveOut = LI.liveAt(LIS->getMBBStartIdx(Succ));
       if (isLiveOut && isLastMBB) {
         VNInfo *VNI = LI.getVNInfoAt(PrevIndex);
         assert(VNI && "LiveInterval should have VNInfo where it is live.");