Use VirtRegMap's Virt2SplitMap to keep track of the original live ran…

…ge before splitting.

All new virtual registers created for spilling or splitting point back to their original.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125980 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveRangeEdit.cpp

@@ -19,12 +19,18 @@
 
 using namespace llvm;
 
+unsigned LiveRangeEdit::getOriginal(const VirtRegMap &vrm) const {
+  unsigned Orig = vrm.getPreSplitReg(getReg());
+  return Orig ? Orig : getReg();
+}
+
 LiveInterval &LiveRangeEdit::create(MachineRegisterInfo &mri,
                                     LiveIntervals &lis,
                                     VirtRegMap &vrm) {
-  const TargetRegisterClass *RC = mri.getRegClass(parent_.reg);
+  const TargetRegisterClass *RC = mri.getRegClass(getReg());
   unsigned VReg = mri.createVirtualRegister(RC);
   vrm.grow();
+  vrm.setIsSplitFromReg(VReg, getOriginal(vrm));
   LiveInterval &li = lis.getOrCreateInterval(VReg);
   newRegs_.push_back(&li);
   return li;

lib/CodeGen/LiveRangeEdit.h

@@ -73,6 +73,10 @@ class LiveRangeEdit {
   LiveInterval &getParent() const { return parent_; }
   unsigned getReg() const { return parent_.reg; }
 
+  /// getOriginal - Return the original virtual register that parent descends
+  /// from through splitting. The original was not created by splitting.
+  unsigned getOriginal(const VirtRegMap&) const;
+
   /// Iterator for accessing the new registers added by this edit.
   typedef SmallVectorImpl<LiveInterval*>::const_iterator iterator;
   iterator begin() const { return newRegs_.begin()+firstNew_; }

lib/CodeGen/VirtRegMap.h

@@ -214,7 +214,7 @@ namespace llvm {
     }
 
     /// @brief returns the live interval virtReg is split from.
-    unsigned getPreSplitReg(unsigned virtReg) {
+    unsigned getPreSplitReg(unsigned virtReg) const {
       return Virt2SplitMap[virtReg];
     }