Commit 409a1aa0 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

MachineCopyPropagation: Respect implicit operands of COPY 

Cherry pick llvm r294088 to 4.0 branch with slight changes to the way
undef operands are handled.

llvm-svn: 294473
parent 8f870305

llvm/lib/CodeGen/MachineCopyPropagation.cpp

+31 −17
Original line number Diff line number Diff line
@@ -61,6 +61,7 @@ namespace { 


  private:

    void ClobberRegister(unsigned Reg);

    void ReadRegister(unsigned Reg);

    void CopyPropagateBlock(MachineBasicBlock &MBB);

    bool eraseIfRedundant(MachineInstr &Copy, unsigned Src, unsigned Def);
@@ -120,6 +121,18 @@ void MachineCopyPropagation::ClobberRegister(unsigned Reg) { 
  }

}



void MachineCopyPropagation::ReadRegister(unsigned Reg) {

  // If 'Reg' is defined by a copy, the copy is no longer a candidate

  // for elimination.

  for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {

    Reg2MIMap::iterator CI = CopyMap.find(*AI);

    if (CI != CopyMap.end()) {

      DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());

      MaybeDeadCopies.remove(CI->second);

    }

  }

}



/// Return true if \p PreviousCopy did copy register \p Src to register \p Def.

/// This fact may have been obscured by sub register usage or may not be true at

/// all even though Src and Def are subregisters of the registers used in
@@ -212,12 +225,14 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) { 


      // If Src is defined by a previous copy, the previous copy cannot be

      // eliminated.

      for (MCRegAliasIterator AI(Src, TRI, true); AI.isValid(); ++AI) {

        Reg2MIMap::iterator CI = CopyMap.find(*AI);

        if (CI != CopyMap.end()) {

          DEBUG(dbgs() << "MCP: Copy is no longer dead: "; CI->second->dump());

          MaybeDeadCopies.remove(CI->second);

        }

      ReadRegister(Src);

      for (const MachineOperand &MO : MI->implicit_operands()) {

        if (!MO.isReg() || !MO.readsReg())

          continue;

        unsigned Reg = MO.getReg();

        if (!Reg)

          continue;

        ReadRegister(Reg);

      }



      DEBUG(dbgs() << "MCP: Copy is a deletion candidate: "; MI->dump());
@@ -234,6 +249,14 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) { 
      // ...

      // %xmm2<def> = copy %xmm9

      ClobberRegister(Def);

      for (const MachineOperand &MO : MI->implicit_operands()) {

        if (!MO.isReg() || !MO.isDef())

          continue;

        unsigned Reg = MO.getReg();

        if (!Reg)

          continue;

        ClobberRegister(Reg);

      }



      // Remember Def is defined by the copy.

      for (MCSubRegIterator SR(Def, TRI, /*IncludeSelf=*/true); SR.isValid();
@@ -268,17 +291,8 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) { 


      if (MO.isDef()) {

        Defs.push_back(Reg);

        continue;

      }



      // If 'Reg' is defined by a copy, the copy is no longer a candidate

      // for elimination.

      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {

        Reg2MIMap::iterator CI = CopyMap.find(*AI);

        if (CI != CopyMap.end()) {

          DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());

          MaybeDeadCopies.remove(CI->second);

        }

      } else {

        ReadRegister(Reg);

      }

      // Treat undef use like defs for copy propagation but not for

      // dead copy. We would need to do a liveness check to be sure the copy