[llvm-commits] [llvm] r169060 - /llvm/trunk/lib/CodeGen/MachineCopyPropagation.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Fri Nov 30 17:53:00 2012
New Revision: 169060

URL: http://llvm.org/viewvc/llvm-project?rev=169060&view=rev
Log:
Convert COPY instructions into KILLs if they have implicit defs.

MachineCopyPropagation doesn't understand super-register liveness well
enough to be able to remove implicit defs of super-registers.

This fixes a problem in ARM/2012-01-26-CopyPropKills.ll that is exposed
by an future TwoAddressInstructionPass change. The KILL instructions are
removed before the machine code is emitted.

Modified:
    llvm/trunk/lib/CodeGen/MachineCopyPropagation.cpp

Modified: llvm/trunk/lib/CodeGen/MachineCopyPropagation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineCopyPropagation.cpp?rev=169060&r1=169059&r2=169060&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineCopyPropagation.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineCopyPropagation.cpp Fri Nov 30 17:53:00 2012
@@ -17,6 +17,7 @@
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -32,6 +33,7 @@
 namespace {
   class MachineCopyPropagation : public MachineFunctionPass {
     const TargetRegisterInfo *TRI;
+    const TargetInstrInfo *TII;
     MachineRegisterInfo *MRI;
 
   public:
@@ -50,6 +52,7 @@
                                  SourceMap &SrcMap,
                                  DenseMap<unsigned, MachineInstr*> &AvailCopyMap);
     bool CopyPropagateBlock(MachineBasicBlock &MBB);
+    void removeCopy(MachineInstr *MI);
   };
 }
 char MachineCopyPropagation::ID = 0;
@@ -123,6 +126,16 @@
   return false;
 }
 
+// Remove MI from the function because it has been determined it is dead.
+// Turn it into a noop KILL instruction if it has super-register liveness
+// adjustments.
+void MachineCopyPropagation::removeCopy(MachineInstr *MI) {
+  if (MI->getNumOperands() == 2)
+    MI->eraseFromParent();
+  else
+    MI->setDesc(TII->get(TargetOpcode::KILL));
+}
+
 bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
   SmallSetVector<MachineInstr*, 8> MaybeDeadCopies;  // Candidates for deletion
   DenseMap<unsigned, MachineInstr*> AvailCopyMap;    // Def -> available copies map
@@ -168,7 +181,7 @@
           for (MachineBasicBlock::iterator I = CopyMI, E = MI; I != E; ++I)
             I->clearRegisterKills(Def, TRI);
 
-          MI->eraseFromParent();
+          removeCopy(MI);
           Changed = true;
           ++NumDeletes;
           continue;
@@ -261,7 +274,7 @@
         unsigned Reg = (*DI)->getOperand(0).getReg();
         if (MRI->isReserved(Reg) || !MaskMO.clobbersPhysReg(Reg))
           continue;
-        (*DI)->eraseFromParent();
+        removeCopy(*DI);
         Changed = true;
         ++NumDeletes;
       }
@@ -297,7 +310,7 @@
            DI = MaybeDeadCopies.begin(), DE = MaybeDeadCopies.end();
          DI != DE; ++DI) {
       if (!MRI->isReserved((*DI)->getOperand(0).getReg())) {
-        (*DI)->eraseFromParent();
+        removeCopy(*DI);
         Changed = true;
         ++NumDeletes;
       }
@@ -311,6 +324,7 @@
   bool Changed = false;
 
   TRI = MF.getTarget().getRegisterInfo();
+  TII = MF.getTarget().getInstrInfo();
   MRI = &MF.getRegInfo();
 
   for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)