Fixes to r153903. Added missing explanation of behaviour when the VirtRegMap is NULL. Also changed it in this case to just avoid updating the map, but live ranges or intervals will still get updated and created

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153914 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 10 insertions, 5 deletions

diff --git a/include/llvm/CodeGen/LiveRangeEdit.h b/include/llvm/CodeGen/LiveRangeEdit.h
index 909130ff61..57a619389f 100644
--- a/include/llvm/CodeGen/LiveRangeEdit.h
+++ b/include/llvm/CodeGen/LiveRangeEdit.h
@@ -94,6 +94,11 @@ public:
   /// @param parent The register being spilled or split.
   /// @param newRegs List to receive any new registers created. This needn't be
   ///                empty initially, any existing registers are ignored.
+  /// @param MF The MachineFunction the live range edit is taking place in.
+  /// @param lis The collection of all live intervals in this function.
+  /// @param vrm Map of virtual registers to physical registers for this
+  ///            function.  If NULL, no virtual register map updates will
+  ///            be done.  This could be the case if called before Regalloc.
   LiveRangeEdit(LiveInterval &parent,
                 SmallVectorImpl<LiveInterval*> &newRegs,
                 MachineFunction &MF,
diff --git a/lib/CodeGen/LiveRangeEdit.cpp b/lib/CodeGen/LiveRangeEdit.cpp
index 52e366cb7d..4ecb2d9a60 100644
--- a/lib/CodeGen/LiveRangeEdit.cpp
+++ b/lib/CodeGen/LiveRangeEdit.cpp
@@ -33,8 +33,10 @@ void LiveRangeEdit::Delegate::anchor() { }
 
 LiveInterval &LiveRangeEdit::createFrom(unsigned OldReg) {
   unsigned VReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
-  VRM->grow();
-  VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg));
+  if (VRM) {
+    VRM->grow();
+    VRM->setIsSplitFromReg(VReg, VRM->getOriginal(OldReg));
+  }
   LiveInterval &LI = LIS.getOrCreateInterval(VReg);
   newRegs_.push_back(&LI);
   return LI;
@@ -270,8 +272,6 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
       delegate_->LRE_WillShrinkVirtReg(LI->reg);
     if (!LIS.shrinkToUses(LI, &Dead))
       continue;
-    if (!VRM)
-      continue;
     
     // Don't create new intervals for a register being spilled.
     // The new intervals would have to be spilled anyway so its not worth it.
@@ -295,7 +295,7 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
     if (NumComp <= 1)
       continue;
     ++NumFracRanges;
-    bool IsOriginal = VRM->getOriginal(LI->reg) == LI->reg;
+    bool IsOriginal = VRM && VRM->getOriginal(LI->reg) == LI->reg;
     DEBUG(dbgs() << NumComp << " components: " << *LI << '\n');
     SmallVector<LiveInterval*, 8> Dups(1, LI);
     for (unsigned i = 1; i != NumComp; ++i) {