| //===- X86InstrInfo.cpp - X86 Instruction Information -----------*- C++ -*-===// |
| // |
| // 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. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains the X86 implementation of the TargetInstrInfo class. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "X86InstrInfo.h" |
| #include "X86.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| |
| #include "X86GenInstrInfo.inc" |
| |
| using namespace llvm; |
| |
| X86InstrInfo::X86InstrInfo() |
| : TargetInstrInfo(X86Insts, sizeof(X86Insts)/sizeof(X86Insts[0]), 0) { |
| } |
| |
| |
| // createNOPinstr - returns the target's implementation of NOP, which is |
| // usually a pseudo-instruction, implemented by a degenerate version of |
| // another instruction, e.g. X86: `xchg ax, ax'; SparcV9: `sethi r0, r0, r0' |
| // |
| MachineInstr* X86InstrInfo::createNOPinstr() const { |
| return BuildMI(X86::XCHGrr16, 2).addReg(X86::AX, MOTy::UseAndDef) |
| .addReg(X86::AX, MOTy::UseAndDef); |
| } |
| |
| |
| /// isNOPinstr - not having a special NOP opcode, we need to know if a given |
| /// instruction is interpreted as an `official' NOP instr, i.e., there may be |
| /// more than one way to `do nothing' but only one canonical way to slack off. |
| // |
| bool X86InstrInfo::isNOPinstr(const MachineInstr &MI) const { |
| // Make sure the instruction is EXACTLY `xchg ax, ax' |
| if (MI.getOpcode() == X86::XCHGrr16) { |
| const MachineOperand &op0 = MI.getOperand(0), &op1 = MI.getOperand(1); |
| if (op0.isMachineRegister() && op0.getMachineRegNum() == X86::AX && |
| op1.isMachineRegister() && op1.getMachineRegNum() == X86::AX) { |
| return true; |
| } |
| } |
| // FIXME: there are several NOOP instructions, we should check for them here. |
| return false; |
| } |
| |