//===-- X86EncodingOptimization.cpp - X86 Encoding optimization -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the implementation of the X86 encoding optimization
//
//===----------------------------------------------------------------------===//
#include "X86EncodingOptimization.h"
#include "X86BaseInfo.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/Support/Casting.h"
using namespace llvm;
bool X86::optimizeInstFromVEX3ToVEX2(MCInst &MI, const MCInstrDesc &Desc) {
unsigned OpIdx1, OpIdx2;
unsigned Opcode = MI.getOpcode();
unsigned NewOpc = 0;
#define FROM_TO(FROM, TO, IDX1, IDX2) \
case X86::FROM: \
NewOpc = X86::TO; \
OpIdx1 = IDX1; \
OpIdx2 = IDX2; \
break;
#define TO_REV(FROM) FROM_TO(FROM, FROM##_REV, 0, 1)
switch (Opcode) {
default: {
// If the instruction is a commutable arithmetic instruction we might be
// able to commute the operands to get a 2 byte VEX prefix.
uint64_t TSFlags = Desc.TSFlags;
if (!Desc.isCommutable() || (TSFlags & X86II::EncodingMask) != X86II::VEX ||
(TSFlags & X86II::OpMapMask) != X86II::TB ||
(TSFlags & X86II::FormMask) != X86II::MRMSrcReg ||
(TSFlags & X86II::REX_W) || !(TSFlags & X86II::VEX_4V) ||
MI.getNumOperands() != 3)
return false;
// These two are not truly commutable.
if (Opcode == X86::VMOVHLPSrr || Opcode == X86::VUNPCKHPDrr)
return false;
OpIdx1 = 1;
OpIdx2 = 2;
break;
}
case X86::VCMPPDrri:
case X86::VCMPPDYrri:
case X86::VCMPPSrri:
case X86::VCMPPSYrri:
case X86::VCMPSDrri:
case X86::VCMPSSrri: {
switch (MI.getOperand(3).getImm() & 0x7) {
default:
return false;
case 0x00: // EQUAL
case 0x03: // UNORDERED
case 0x04: // NOT EQUAL
case 0x07: // ORDERED
OpIdx1 = 1;
OpIdx2 = 2;
break;
}
break;
}
// Commute operands to get a smaller encoding by using VEX.R instead of
// VEX.B if one of the registers is extended, but other isn't.
FROM_TO(VMOVZPQILo2PQIrr, VMOVPQI2QIrr, 0, 1)
TO_REV(VMOVAPDrr)
TO_REV(VMOVAPDYrr)
TO_REV(VMOVAPSrr)
TO_REV(VMOVAPSYrr)
TO_REV(VMOVDQArr)
TO_REV(VMOVDQAYrr)
TO_REV(VMOVDQUrr)
TO_REV(VMOVDQUYrr)
TO_REV(VMOVUPDrr)
TO_REV(VMOVUPDYrr)
TO_REV(VMOVUPSrr)
TO_REV(VMOVUPSYrr)
#undef TO_REV
#define TO_REV(FROM) FROM_TO(FROM, FROM##_REV, 0, 2)
TO_REV(VMOVSDrr)
TO_REV(VMOVSSrr)
#undef TO_REV
#undef FROM_TO
}
if (X86II::isX86_64ExtendedReg(MI.getOperand(OpIdx1).getReg()) ||
!X86II::isX86_64ExtendedReg(MI.getOperand(OpIdx2).getReg()))
return false;
if (NewOpc)
MI.setOpcode(NewOpc);
else
std::swap(MI.getOperand(OpIdx1), MI.getOperand(OpIdx2));
return true;
}
// NOTE: We may write this as an InstAlias if it's only used by AsmParser. See
// validateTargetOperandClass.
bool X86::optimizeShiftRotateWithImmediateOne(MCInst &MI) {
unsigned NewOpc;
#define TO_IMM1(FROM) \
case X86::FROM##i: \
NewOpc = X86::FROM##1; \
break; \
case X86::FROM##i_EVEX: \
NewOpc = X86::FROM##1_EVEX; \
break; \
case X86::FROM##i_ND: \
NewOpc = X86::FROM##1_ND; \
break;
switch (MI.getOpcode()) {
default:
return false;
TO_IMM1(RCR8r)
TO_IMM1(RCR16r)
TO_IMM1(RCR32r)
TO_IMM1(RCR64r)
TO_IMM1(RCL8r)
TO_IMM1(RCL16r)
TO_IMM1(RCL32r)
TO_IMM1(RCL64r)
TO_IMM1(RCR8m)
TO_IMM1(RCR16m)
TO_IMM1(RCR32m)
TO_IMM1(RCR64m)
TO_IMM1(RCL8m)
TO_IMM1(RCL16m)
TO_IMM1(RCL32m)
TO_IMM1(RCL64m)
#undef TO_IMM1
#define TO_IMM1(FROM) \
case X86::FROM##i: \
NewOpc = X86::FROM##1; \
break; \
case X86::FROM##i_EVEX: \
NewOpc = X86::FROM##1_EVEX; \
break; \
case X86::FROM##i_NF: \
NewOpc = X86::FROM##1_NF; \
break; \
case X86::FROM##i_ND: \
NewOpc = X86::FROM##1_ND; \
break; \
case X86::FROM##i_NF_ND: \
NewOpc = X86::FROM##1_NF_ND; \
break;
TO_IMM1(ROR8r)
TO_IMM1(ROR16r)
TO_IMM1(ROR32r)
TO_IMM1(ROR64r)
TO_IMM1(ROL8r)
TO_IMM1(ROL16r)
TO_IMM1(ROL32r)
TO_IMM1(ROL64r)
TO_IMM1(SAR8r)
TO_IMM1(SAR16r)
TO_IMM1(SAR32r)
TO_IMM1(SAR64r)
TO_IMM1(SHR8r)
TO_IMM1(SHR16r)
TO_IMM1(SHR32r)
TO_IMM1(SHR64r)
TO_IMM1(SHL8r)
TO_IMM1(SHL16r)
TO_IMM1(SHL32r)
TO_IMM1(SHL64r)
TO_IMM1(ROR8m)
TO_IMM1(ROR16m)
TO_IMM1(ROR32m)
TO_IMM1(ROR64m)
TO_IMM1(ROL8m)
TO_IMM1(ROL16m)
TO_IMM1(ROL32m)
TO_IMM1(ROL64m)
TO_IMM1(SAR8m)
TO_IMM1(SAR16m)
TO_IMM1(SAR32m)
TO_IMM1(SAR64m)
TO_IMM1(SHR8m)
TO_IMM1(SHR16m)
TO_IMM1(SHR32m)
TO_IMM1(SHR64m)
TO_IMM1(SHL8m)
TO_IMM1(SHL16m)
TO_IMM1(SHL32m)
TO_IMM1(SHL64m)
#undef TO_IMM1
}
MCOperand &LastOp = MI.getOperand(MI.getNumOperands() - 1);
if (!LastOp.isImm() || LastOp.getImm() != 1)
return false;
MI.setOpcode(NewOpc);
MI.erase(&LastOp);
return true;
}
bool X86::optimizeVPCMPWithImmediateOneOrSix(MCInst &MI) {
unsigned Opc1;
unsigned Opc2;
#define FROM_TO(FROM, TO1, TO2) \
case X86::FROM: \
Opc1 = X86::TO1; \
Opc2 = X86::TO2; \
break;
switch (MI.getOpcode()) {
default:
return false;
FROM_TO(VPCMPBZ128rmi, VPCMPEQBZ128rm, VPCMPGTBZ128rm)
FROM_TO(VPCMPBZ128rmik, VPCMPEQBZ128rmk, VPCMPGTBZ128rmk)
FROM_TO(VPCMPBZ128rri, VPCMPEQBZ128rr, VPCMPGTBZ128rr)
FROM_TO(VPCMPBZ128rrik, VPCMPEQBZ128rrk, VPCMPGTBZ128rrk)
FROM_TO(VPCMPBZ256rmi, VPCMPEQBZ256rm, VPCMPGTBZ256rm)
FROM_TO(VPCMPBZ256rmik, VPCMPEQBZ256rmk, VPCMPGTBZ256rmk)
FROM_TO(VPCMPBZ256rri, VPCMPEQBZ256rr, VPCMPGTBZ256rr)
FROM_TO(VPCMPBZ256rrik, VPCMPEQBZ256rrk, VPCMPGTBZ256rrk)
FROM_TO(VPCMPBZrmi, VPCMPEQBZrm, VPCMPGTBZrm)
FROM_TO(VPCMPBZrmik, VPCMPEQBZrmk, VPCMPGTBZrmk)
FROM_TO(VPCMPBZrri, VPCMPEQBZrr, VPCMPGTBZrr)
FROM_TO(VPCMPBZrrik, VPCMPEQBZrrk, VPCMPGTBZrrk)
FROM_TO(VPCMPDZ128rmi, VPCMPEQDZ128rm, VPCMPGTDZ128rm)
FROM_TO(VPCMPDZ128rmib, VPCMPEQDZ128rmb, VPCMPGTDZ128rmb)
FROM_TO(VPCMPDZ128rmibk, VPCMPEQDZ128rmbk, VPCMPGTDZ128rmbk)
FROM_TO(VPCMPDZ128rmik, VPCMPEQDZ128rmk, VPCMPGTDZ128rmk)
FROM_TO(VPCMPDZ128rri, VPCMPEQDZ128rr, VPCMPGTDZ128rr)
FROM_TO(VPCMPDZ128rrik, VPCMPEQDZ128rrk, VPCMPGTDZ128rrk)
FROM_TO(VPCMPDZ256rmi, VPCMPEQDZ256rm, VPCMPGTDZ256rm)
FROM_TO(VPCMPDZ256rmib, VPCMPEQDZ256rmb, VPCMPGTDZ256rmb)
FROM_TO(VPCMPDZ256rmibk, VPCMPEQDZ256rmbk, VPCMPGTDZ256rmbk)
FROM_TO(VPCMPDZ256rmik, VPCMPEQDZ256rmk, VPCMPGTDZ256rmk)
FROM_TO(VPCMPDZ256rri, VPCMPEQDZ256rr, VPCMPGTDZ256rr)
FROM_TO(VPCMPDZ256rrik, VPCMPEQDZ256rrk, VPCMPGTDZ256rrk)
FROM_TO(VPCMPDZrmi, VPCMPEQDZrm, VPCMPGTDZrm)
FROM_TO(VPCMPDZrmib, VPCMPEQDZrmb, VPCMPGTDZrmb)
FROM_TO(VPCMPDZrmibk, VPCMPEQDZrmbk, VPCMPGTDZrmbk)
FROM_TO(VPCMPDZrmik, VPCMPEQDZrmk, VPCMPGTDZrmk)
FROM_TO(VPCMPDZrri, VPCMPEQDZrr, VPCMPGTDZrr)
FROM_TO(VPCMPDZrrik, VPCMPEQDZrrk, VPCMPGTDZrrk)
FROM_TO(VPCMPQZ128rmi, VPCMPEQQZ128rm, VPCMPGTQZ128rm)
FROM_TO(VPCMPQZ128rmib, VPCMPEQQZ128rmb, VPCMPGTQZ128rmb)
FROM_TO(VPCMPQZ128rmibk, VPCMPEQQZ128rmbk, VPCMPGTQZ128rmbk)
FROM_TO(VPCMPQZ128rmik, VPCMPEQQZ128rmk, VPCMPGTQZ128rmk)
FROM_TO(VPCMPQZ128rri, VPCMPEQQZ128rr, VPCMPGTQZ128rr)
FROM_TO(VPCMPQZ128rrik, VPCMPEQQZ128rrk, VPCMPGTQZ128rrk)
FROM_TO(VPCMPQZ256rmi, VPCMPEQQZ256rm, VPCMPGTQZ256rm)
FROM_TO(VPCMPQZ256rmib, VPCMPEQQZ256rmb, VPCMPGTQZ256rmb)
FROM_TO(VPCMPQZ256rmibk, VPCMPEQQZ256rmbk, VPCMPGTQZ256rmbk)
FROM_TO(VPCMPQZ256rmik, VPCMPEQQZ256rmk, VPCMPGTQZ256rmk)
FROM_TO(VPCMPQZ256rri, VPCMPEQQZ256rr, VPCMPGTQZ256rr)
FROM_TO(VPCMPQZ256rrik, VPCMPEQQZ256rrk, VPCMPGTQZ256rrk)
FROM_TO(VPCMPQZrmi, VPCMPEQQZrm, VPCMPGTQZrm)
FROM_TO(VPCMPQZrmib, VPCMPEQQZrmb, VPCMPGTQZrmb)
FROM_TO(VPCMPQZrmibk, VPCMPEQQZrmbk, VPCMPGTQZrmbk)
FROM_TO(VPCMPQZrmik, VPCMPEQQZrmk, VPCMPGTQZrmk)
FROM_TO(VPCMPQZrri, VPCMPEQQZrr, VPCMPGTQZrr)
FROM_TO(VPCMPQZrrik, VPCMPEQQZrrk, VPCMPGTQZrrk)
FROM_TO(VPCMPWZ128rmi, VPCMPEQWZ128rm, VPCMPGTWZ128rm)
FROM_TO(VPCMPWZ128rmik, VPCMPEQWZ128rmk, VPCMPGTWZ128rmk)
FROM_TO(VPCMPWZ128rri, VPCMPEQWZ128rr, VPCMPGTWZ128rr)
FROM_TO(VPCMPWZ128rrik, VPCMPEQWZ128rrk, VPCMPGTWZ128rrk)
FROM_TO(VPCMPWZ256rmi, VPCMPEQWZ256rm, VPCMPGTWZ256rm)
FROM_TO(VPCMPWZ256rmik, VPCMPEQWZ256rmk, VPCMPGTWZ256rmk)
FROM_TO(VPCMPWZ256rri, VPCMPEQWZ256rr, VPCMPGTWZ256rr)
FROM_TO(VPCMPWZ256rrik, VPCMPEQWZ256rrk, VPCMPGTWZ256rrk)
FROM_TO(VPCMPWZrmi, VPCMPEQWZrm, VPCMPGTWZrm)
FROM_TO(VPCMPWZrmik, VPCMPEQWZrmk, VPCMPGTWZrmk)
FROM_TO(VPCMPWZrri, VPCMPEQWZrr, VPCMPGTWZrr)
FROM_TO(VPCMPWZrrik, VPCMPEQWZrrk, VPCMPGTWZrrk)
#undef FROM_TO
}
MCOperand &LastOp = MI.getOperand(MI.getNumOperands() - 1);
int64_t Imm = LastOp.getImm();
unsigned NewOpc;
if (Imm == 0)
NewOpc = Opc1;
else if(Imm == 6)
NewOpc = Opc2;
else
return false;
MI.setOpcode(NewOpc);
MI.erase(&LastOp);
return true;
}
bool X86::optimizeMOVSX(MCInst &MI) {
unsigned NewOpc;
#define FROM_TO(FROM, TO, R0, R1) \
case X86::FROM: \
if (MI.getOperand(0).getReg() != X86::R0 || \
MI.getOperand(1).getReg() != X86::R1) \
return false; \
NewOpc = X86::TO; \
break;
switch (MI.getOpcode()) {
default:
return false;
FROM_TO(MOVSX16rr8, CBW, AX, AL) // movsbw %al, %ax --> cbtw
FROM_TO(MOVSX32rr16, CWDE, EAX, AX) // movswl %ax, %eax --> cwtl
FROM_TO(MOVSX64rr32, CDQE, RAX, EAX) // movslq %eax, %rax --> cltq
#undef FROM_TO
}
MI.clear();
MI.setOpcode(NewOpc);
return true;
}
bool X86::optimizeINCDEC(MCInst &MI, bool In64BitMode) {
if (In64BitMode)
return false;
unsigned NewOpc;
// If we aren't in 64-bit mode we can use the 1-byte inc/dec instructions.
#define FROM_TO(FROM, TO) \
case X86::FROM: \
NewOpc = X86::TO; \
break;
switch (MI.getOpcode()) {
default:
return false;
FROM_TO(DEC16r, DEC16r_alt)
FROM_TO(DEC32r, DEC32r_alt)
FROM_TO(INC16r, INC16r_alt)
FROM_TO(INC32r, INC32r_alt)
}
MI.setOpcode(NewOpc);
return true;
}
static bool isARegister(unsigned Reg) {
return Reg == X86::AL || Reg == X86::AX || Reg == X86::EAX || Reg == X86::RAX;
}
/// Simplify things like MOV32rm to MOV32o32a.
bool X86::optimizeMOV(MCInst &MI, bool In64BitMode) {
// Don't make these simplifications in 64-bit mode; other assemblers don't
// perform them because they make the code larger.
if (In64BitMode)
return false;
unsigned NewOpc;
// We don't currently select the correct instruction form for instructions
// which have a short %eax, etc. form. Handle this by custom lowering, for
// now.
//
// Note, we are currently not handling the following instructions:
// MOV64ao8, MOV64o8a
// XCHG16ar, XCHG32ar, XCHG64ar
switch (MI.getOpcode()) {
default:
return false;
FROM_TO(MOV8mr_NOREX, MOV8o32a)
FROM_TO(MOV8mr, MOV8o32a)
FROM_TO(MOV8rm_NOREX, MOV8ao32)
FROM_TO(MOV8rm, MOV8ao32)
FROM_TO(MOV16mr, MOV16o32a)
FROM_TO(MOV16rm, MOV16ao32)
FROM_TO(MOV32mr, MOV32o32a)
FROM_TO(MOV32rm, MOV32ao32)
}
bool IsStore = MI.getOperand(0).isReg() && MI.getOperand(1).isReg();
unsigned AddrBase = IsStore;
unsigned RegOp = IsStore ? 0 : 5;
unsigned AddrOp = AddrBase + 3;
// Check whether the destination register can be fixed.
unsigned Reg = MI.getOperand(RegOp).getReg();
if (!isARegister(Reg))
return false;
// Check whether this is an absolute address.
// FIXME: We know TLVP symbol refs aren't, but there should be a better way
// to do this here.
bool Absolute = true;
if (MI.getOperand(AddrOp).isExpr()) {
const MCExpr *MCE = MI.getOperand(AddrOp).getExpr();
if (const MCSymbolRefExpr *SRE = dyn_cast<MCSymbolRefExpr>(MCE))
if (SRE->getKind() == MCSymbolRefExpr::VK_TLVP)
Absolute = false;
}
if (Absolute && (MI.getOperand(AddrBase + X86::AddrBaseReg).getReg() != 0 ||
MI.getOperand(AddrBase + X86::AddrScaleAmt).getImm() != 1 ||
MI.getOperand(AddrBase + X86::AddrIndexReg).getReg() != 0))
return false;
// If so, rewrite the instruction.
MCOperand Saved = MI.getOperand(AddrOp);
MCOperand Seg = MI.getOperand(AddrBase + X86::AddrSegmentReg);
MI.clear();
MI.setOpcode(NewOpc);
MI.addOperand(Saved);
MI.addOperand(Seg);
return true;
}
/// Simplify FOO $imm, %{al,ax,eax,rax} to FOO $imm, for instruction with
/// a short fixed-register form.
static bool optimizeToFixedRegisterForm(MCInst &MI) {
unsigned NewOpc;
switch (MI.getOpcode()) {
default:
return false;
FROM_TO(ADC8ri, ADC8i8)
FROM_TO(ADC16ri, ADC16i16)
FROM_TO(ADC32ri, ADC32i32)
FROM_TO(ADC64ri32, ADC64i32)
FROM_TO(ADD8ri, ADD8i8)
FROM_TO(ADD16ri, ADD16i16)
FROM_TO(ADD32ri, ADD32i32)
FROM_TO(ADD64ri32, ADD64i32)
FROM_TO(AND8ri, AND8i8)
FROM_TO(AND16ri, AND16i16)
FROM_TO(AND32ri, AND32i32)
FROM_TO(AND64ri32, AND64i32)
FROM_TO(CMP8ri, CMP8i8)
FROM_TO(CMP16ri, CMP16i16)
FROM_TO(CMP32ri, CMP32i32)
FROM_TO(CMP64ri32, CMP64i32)
FROM_TO(OR8ri, OR8i8)
FROM_TO(OR16ri, OR16i16)
FROM_TO(OR32ri, OR32i32)
FROM_TO(OR64ri32, OR64i32)
FROM_TO(SBB8ri, SBB8i8)
FROM_TO(SBB16ri, SBB16i16)
FROM_TO(SBB32ri, SBB32i32)
FROM_TO(SBB64ri32, SBB64i32)
FROM_TO(SUB8ri, SUB8i8)
FROM_TO(SUB16ri, SUB16i16)
FROM_TO(SUB32ri, SUB32i32)
FROM_TO(SUB64ri32, SUB64i32)
FROM_TO(TEST8ri, TEST8i8)
FROM_TO(TEST16ri, TEST16i16)
FROM_TO(TEST32ri, TEST32i32)
FROM_TO(TEST64ri32, TEST64i32)
FROM_TO(XOR8ri, XOR8i8)
FROM_TO(XOR16ri, XOR16i16)
FROM_TO(XOR32ri, XOR32i32)
FROM_TO(XOR64ri32, XOR64i32)
}
// Check whether the destination register can be fixed.
unsigned Reg = MI.getOperand(0).getReg();
if (!isARegister(Reg))
return false;
// If so, rewrite the instruction.
MCOperand Saved = MI.getOperand(MI.getNumOperands() - 1);
MI.clear();
MI.setOpcode(NewOpc);
MI.addOperand(Saved);
return true;
}
unsigned X86::getOpcodeForShortImmediateForm(unsigned Opcode) {
#define ENTRY(LONG, SHORT) \
case X86::LONG: \
return X86::SHORT;
switch (Opcode) {
default:
return Opcode;
#include "X86EncodingOptimizationForImmediate.def"
}
}
unsigned X86::getOpcodeForLongImmediateForm(unsigned Opcode) {
#define ENTRY(LONG, SHORT) \
case X86::SHORT: \
return X86::LONG;
switch (Opcode) {
default:
return Opcode;
#include "X86EncodingOptimizationForImmediate.def"
}
}
static bool optimizeToShortImmediateForm(MCInst &MI) {
unsigned NewOpc;
#define ENTRY(LONG, SHORT) \
case X86::LONG: \
NewOpc = X86::SHORT; \
break;
switch (MI.getOpcode()) {
default:
return false;
#include "X86EncodingOptimizationForImmediate.def"
}
unsigned SkipOperands = X86::isCCMPCC(MI.getOpcode()) ? 2 : 0;
MCOperand &LastOp = MI.getOperand(MI.getNumOperands() - 1 - SkipOperands);
if (LastOp.isExpr()) {
const MCSymbolRefExpr *SRE = dyn_cast<MCSymbolRefExpr>(LastOp.getExpr());
if (!SRE || SRE->getKind() != MCSymbolRefExpr::VK_X86_ABS8)
return false;
} else if (LastOp.isImm()) {
if (!isInt<8>(LastOp.getImm()))
return false;
}
MI.setOpcode(NewOpc);
return true;
}
bool X86::optimizeToFixedRegisterOrShortImmediateForm(MCInst &MI) {
// We may optimize twice here.
bool ShortImm = optimizeToShortImmediateForm(MI);
bool FixedReg = optimizeToFixedRegisterForm(MI);
return ShortImm || FixedReg;
}