Use VirtRegMap's Virt2SplitMap to keep track of the original live range before splitting.

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

llvm-svn: 125980

3 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/LiveRangeEdit.cpp b/llvm/lib/CodeGen/LiveRangeEdit.cpp
index 3c7d9f66e74..e23f3828343 100644
--- a/llvm/lib/CodeGen/LiveRangeEdit.cpp
+++ b/llvm/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;
diff --git a/llvm/lib/CodeGen/LiveRangeEdit.h b/llvm/lib/CodeGen/LiveRangeEdit.h
index 73f69ed6398..832a12db4f4 100644
--- a/llvm/lib/CodeGen/LiveRangeEdit.h
+++ b/llvm/lib/CodeGen/LiveRangeEdit.h
@@ -73,6 +73,10 @@ public:
   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_; }
diff --git a/llvm/lib/CodeGen/VirtRegMap.h b/llvm/lib/CodeGen/VirtRegMap.h
index a43ac5fc82d..23101ce74f9 100644
--- a/llvm/lib/CodeGen/VirtRegMap.h
+++ b/llvm/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];
     }