| //===-- PeepholeOpts.cpp --------------------------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Support for performing several peephole opts in one or a few passes over the |
| // machine code of a method. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "SparcInternals.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| #include "llvm/BasicBlock.h" |
| #include "llvm/Pass.h" |
| |
| namespace llvm { |
| |
| //************************* Internal Functions *****************************/ |
| |
| static inline void |
| DeleteInstruction(MachineBasicBlock& mvec, |
| MachineBasicBlock::iterator& BBI, |
| const TargetMachine& target) { |
| // Check if this instruction is in a delay slot of its predecessor. |
| if (BBI != mvec.begin()) { |
| const TargetInstrInfo& mii = target.getInstrInfo(); |
| MachineInstr* predMI = *(BBI-1); |
| if (unsigned ndelay = mii.getNumDelaySlots(predMI->getOpCode())) { |
| // This instruction is in a delay slot of its predecessor, so |
| // replace it with a nop. By replacing in place, we save having |
| // to update the I-I maps. |
| // |
| assert(ndelay == 1 && "Not yet handling multiple-delay-slot targets"); |
| (*BBI)->replace(mii.getNOPOpCode(), 0); |
| return; |
| } |
| } |
| |
| // The instruction is not in a delay slot, so we can simply erase it. |
| mvec.erase(BBI); |
| BBI = mvec.end(); |
| } |
| |
| //******************* Individual Peephole Optimizations ********************/ |
| |
| //---------------------------------------------------------------------------- |
| // Function: IsUselessCopy |
| // Decide whether a machine instruction is a redundant copy: |
| // -- ADD with g0 and result and operand are identical, or |
| // -- OR with g0 and result and operand are identical, or |
| // -- FMOVS or FMOVD and result and operand are identical. |
| // Other cases are possible but very rare that they would be useless copies, |
| // so it's not worth analyzing them. |
| //---------------------------------------------------------------------------- |
| |
| static bool IsUselessCopy(const TargetMachine &target, const MachineInstr* MI) { |
| if (MI->getOpCode() == V9::FMOVS || MI->getOpCode() == V9::FMOVD) { |
| return (/* both operands are allocated to the same register */ |
| MI->getOperand(0).getAllocatedRegNum() == |
| MI->getOperand(1).getAllocatedRegNum()); |
| } else if (MI->getOpCode() == V9::ADDr || MI->getOpCode() == V9::ORr || |
| MI->getOpCode() == V9::ADDi || MI->getOpCode() == V9::ORi) { |
| unsigned srcWithDestReg; |
| |
| for (srcWithDestReg = 0; srcWithDestReg < 2; ++srcWithDestReg) |
| if (MI->getOperand(srcWithDestReg).hasAllocatedReg() && |
| MI->getOperand(srcWithDestReg).getAllocatedRegNum() |
| == MI->getOperand(2).getAllocatedRegNum()) |
| break; |
| |
| if (srcWithDestReg == 2) |
| return false; |
| else { |
| /* else source and dest are allocated to the same register */ |
| unsigned otherOp = 1 - srcWithDestReg; |
| return (/* either operand otherOp is register %g0 */ |
| (MI->getOperand(otherOp).hasAllocatedReg() && |
| MI->getOperand(otherOp).getAllocatedRegNum() == |
| target.getRegInfo().getZeroRegNum()) || |
| |
| /* or operand otherOp == 0 */ |
| (MI->getOperand(otherOp).getType() |
| == MachineOperand::MO_SignExtendedImmed && |
| MI->getOperand(otherOp).getImmedValue() == 0)); |
| } |
| } |
| else |
| return false; |
| } |
| |
| inline bool |
| RemoveUselessCopies(MachineBasicBlock& mvec, |
| MachineBasicBlock::iterator& BBI, |
| const TargetMachine& target) { |
| if (IsUselessCopy(target, *BBI)) { |
| DeleteInstruction(mvec, BBI, target); |
| return true; |
| } |
| return false; |
| } |
| |
| |
| //************************ Class Implementations **************************/ |
| |
| class PeepholeOpts: public BasicBlockPass { |
| const TargetMachine ⌖ |
| bool visit(MachineBasicBlock& mvec, |
| MachineBasicBlock::iterator BBI) const; |
| public: |
| PeepholeOpts(const TargetMachine &TM): target(TM) { } |
| bool runOnBasicBlock(BasicBlock &BB); // apply this pass to each BB |
| virtual const char *getPassName() const { return "Peephole Optimization"; } |
| }; |
| |
| // Apply a list of peephole optimizations to this machine instruction |
| // within its local context. They are allowed to delete MI or any |
| // instruction before MI, but not |
| // |
| bool PeepholeOpts::visit(MachineBasicBlock& mvec, |
| MachineBasicBlock::iterator BBI) const { |
| /* Remove redundant copy instructions */ |
| return RemoveUselessCopies(mvec, BBI, target); |
| } |
| |
| |
| bool PeepholeOpts::runOnBasicBlock(BasicBlock &BB) { |
| // Get the machine instructions for this BB |
| // FIXME: MachineBasicBlock::get() is deprecated, hence inlining the function |
| const Function *F = BB.getParent(); |
| MachineFunction &MF = MachineFunction::get(F); |
| MachineBasicBlock *MBB = NULL; |
| for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) |
| if (I->getBasicBlock() == &BB) |
| MBB = I; |
| |
| assert(MBB && "MachineBasicBlock object not found for specified block!"); |
| MachineBasicBlock &mvec = *MBB; |
| |
| // Iterate over all machine instructions in the BB |
| // Use a reverse iterator to allow deletion of MI or any instruction after it. |
| // Insertions or deletions *before* MI are not safe. |
| // |
| for (MachineBasicBlock::reverse_iterator RI=mvec.rbegin(), |
| RE=mvec.rend(); RI != RE; ) { |
| MachineBasicBlock::iterator BBI = RI.base()-1; // save before incr |
| ++RI; // pre-increment to delete MI or after it |
| visit(mvec, BBI); |
| } |
| |
| return true; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // createPeepholeOptsPass - Public entrypoint for peephole optimization |
| // and this file as a whole... |
| // |
| FunctionPass* createPeepholeOptsPass(const TargetMachine &TM) { |
| return new PeepholeOpts(TM); |
| } |
| |
| } // End llvm namespace |