Tell the register allocator about new unused virtual registers.

This allows the allocator to free any resources used by the virtual register,
including physical register assignments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127560 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index 86fd108167..57119aacd2 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -161,6 +161,7 @@ public:
 
 private:
   void LRE_WillEraseInstruction(MachineInstr*);
+  bool LRE_CanEraseVirtReg(unsigned);
 
   bool checkUncachedInterference(LiveInterval&, unsigned);
   LiveInterval *getSingleInterference(LiveInterval&, unsigned);
@@ -249,6 +250,15 @@ void RAGreedy::LRE_WillEraseInstruction(MachineInstr *MI) {
   VRM->RemoveMachineInstrFromMaps(MI);
 }
 
+bool RAGreedy::LRE_CanEraseVirtReg(unsigned VirtReg) {
+  if (unsigned PhysReg = VRM->getPhys(VirtReg)) {
+    unassign(LIS->getInterval(VirtReg), PhysReg);
+    return true;
+  }
+  // Unassigned virtreg is probably in the priority queue.
+  // RegAllocBase will erase it after dequeueing.
+  return false;
+}
 
 void RAGreedy::releaseMemory() {
   SpillerInstance.reset(0);