Refactor LiveRangeEdit::eliminateDeadDefs.

I want to add logic to handle more cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184571 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveRangeEdit.h

@@ -19,6 +19,7 @@
 #define LLVM_CODEGEN_LIVERANGEEDIT_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/CodeGen/LiveInterval.h"
 #include "llvm/Target/TargetMachine.h"
@@ -90,6 +91,12 @@ private:
   /// a load, eliminate the register by folding the def into the use.
   bool foldAsLoad(LiveInterval *LI, SmallVectorImpl<MachineInstr*> &Dead);
 
+  typedef SetVector<LiveInterval*,
+                    SmallVector<LiveInterval*, 8>,
+                    SmallPtrSet<LiveInterval*, 8> > ToShrinkSet;
+  /// Helper for eliminateDeadDefs.
+  void eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink);
+
 public:
   /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
   /// @param parent The register being spilled or split.

lib/CodeGen/LiveRangeEdit.cpp

@@ -13,7 +13,6 @@
 
 #define DEBUG_TYPE "regalloc"
 #include "llvm/CodeGen/LiveRangeEdit.h"
-#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/CalcSpillWeights.h"
 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
@@ -216,30 +215,22 @@ bool LiveRangeEdit::foldAsLoad(LiveInterval *LI,
   return true;
 }
 
-void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
-                                      ArrayRef<unsigned> RegsBeingSpilled) {
-  SetVector<LiveInterval*,
-            SmallVector<LiveInterval*, 8>,
-            SmallPtrSet<LiveInterval*, 8> > ToShrink;
-
-  for (;;) {
-    // Erase all dead defs.
-    while (!Dead.empty()) {
-      MachineInstr *MI = Dead.pop_back_val();
+/// Find all live intervals that need to shrink, then remove the instruction.
+void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
   assert(MI->allDefsAreDead() && "Def isn't really dead");
   SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
 
   // Never delete inline asm.
   if (MI->isInlineAsm()) {
     DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
-        continue;
+    return;
   }
 
   // Use the same criteria as DeadMachineInstructionElim.
   bool SawStore = false;
   if (!MI->isSafeToMove(&TII, 0, SawStore)) {
     DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
-        continue;
+    return;
   }
 
   DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
@@ -317,7 +308,16 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
       eraseVirtReg(Reg);
     }
   }
-    }
+}
+
+void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
+                                      ArrayRef<unsigned> RegsBeingSpilled) {
+  ToShrinkSet ToShrink;
+
+  for (;;) {
+    // Erase all dead defs.
+    while (!Dead.empty())
+      eliminateDeadDef(Dead.pop_back_val(), ToShrink);
 
     if (ToShrink.empty())
       break;