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//===- X86MacroFusion.cpp - X86 Macro Fusion ------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// \file This file contains the X86 implementation of the DAG scheduling
/// mutation to pair instructions back to back.
#include "X86MacroFusion.h"
#include "X86Subtarget.h"
#include "llvm/CodeGen/MacroFusion.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
using namespace llvm;
namespace {
// The classification for the first instruction.
enum class FirstInstrKind { Test, Cmp, And, ALU, IncDec, Invalid };
// The classification for the second instruction (jump).
enum class JumpKind {
// JE, JL, JG and variants.
// JA, JB and variants.
// JS, JP, JO and variants.
// Not a fusable jump.
} // namespace
static FirstInstrKind classifyFirst(const MachineInstr &MI) {
switch (MI.getOpcode()) {
return FirstInstrKind::Invalid;
case X86::TEST8rr:
case X86::TEST16rr:
case X86::TEST32rr:
case X86::TEST64rr:
case X86::TEST8ri:
case X86::TEST16ri:
case X86::TEST32ri:
case X86::TEST64ri32:
case X86::TEST8mr:
case X86::TEST16mr:
case X86::TEST32mr:
case X86::TEST64mr:
return FirstInstrKind::Test;
case X86::AND16ri:
case X86::AND16ri8:
case X86::AND16rm:
case X86::AND16rr:
case X86::AND32ri:
case X86::AND32ri8:
case X86::AND32rm:
case X86::AND32rr:
case X86::AND64ri32:
case X86::AND64ri8:
case X86::AND64rm:
case X86::AND64rr:
case X86::AND8ri:
case X86::AND8rm:
case X86::AND8rr:
return FirstInstrKind::And;
case X86::CMP16ri:
case X86::CMP16ri8:
case X86::CMP16rm:
case X86::CMP16rr:
case X86::CMP16mr:
case X86::CMP32ri:
case X86::CMP32ri8:
case X86::CMP32rm:
case X86::CMP32rr:
case X86::CMP32mr:
case X86::CMP64ri32:
case X86::CMP64ri8:
case X86::CMP64rm:
case X86::CMP64rr:
case X86::CMP64mr:
case X86::CMP8ri:
case X86::CMP8rm:
case X86::CMP8rr:
case X86::CMP8mr:
return FirstInstrKind::Cmp;
case X86::ADD16ri:
case X86::ADD16ri8:
case X86::ADD16ri8_DB:
case X86::ADD16ri_DB:
case X86::ADD16rm:
case X86::ADD16rr:
case X86::ADD16rr_DB:
case X86::ADD32ri:
case X86::ADD32ri8:
case X86::ADD32ri8_DB:
case X86::ADD32ri_DB:
case X86::ADD32rm:
case X86::ADD32rr:
case X86::ADD32rr_DB:
case X86::ADD64ri32:
case X86::ADD64ri32_DB:
case X86::ADD64ri8:
case X86::ADD64ri8_DB:
case X86::ADD64rm:
case X86::ADD64rr:
case X86::ADD64rr_DB:
case X86::ADD8ri:
case X86::ADD8ri_DB:
case X86::ADD8rm:
case X86::ADD8rr:
case X86::ADD8rr_DB:
case X86::SUB16ri:
case X86::SUB16ri8:
case X86::SUB16rm:
case X86::SUB16rr:
case X86::SUB32ri:
case X86::SUB32ri8:
case X86::SUB32rm:
case X86::SUB32rr:
case X86::SUB64ri32:
case X86::SUB64ri8:
case X86::SUB64rm:
case X86::SUB64rr:
case X86::SUB8ri:
case X86::SUB8rm:
case X86::SUB8rr:
return FirstInstrKind::ALU;
case X86::INC16r:
case X86::INC32r:
case X86::INC64r:
case X86::INC8r:
case X86::DEC16r:
case X86::DEC32r:
case X86::DEC64r:
case X86::DEC8r:
return FirstInstrKind::IncDec;
static JumpKind classifySecond(const MachineInstr &MI) {
X86::CondCode CC = X86::getCondFromBranch(MI);
if (CC == X86::COND_INVALID)
return JumpKind::Invalid;
switch (CC) {
return JumpKind::Invalid;
case X86::COND_E:
case X86::COND_NE:
case X86::COND_L:
case X86::COND_LE:
case X86::COND_G:
case X86::COND_GE:
return JumpKind::ELG;
case X86::COND_B:
case X86::COND_BE:
case X86::COND_A:
case X86::COND_AE:
return JumpKind::AB;
case X86::COND_S:
case X86::COND_NS:
case X86::COND_P:
case X86::COND_NP:
case X86::COND_O:
case X86::COND_NO:
return JumpKind::SPO;
/// Check if the instr pair, FirstMI and SecondMI, should be fused
/// together. Given SecondMI, when FirstMI is unspecified, then check if
/// SecondMI may be part of a fused pair at all.
static bool shouldScheduleAdjacent(const TargetInstrInfo &TII,
const TargetSubtargetInfo &TSI,
const MachineInstr *FirstMI,
const MachineInstr &SecondMI) {
const X86Subtarget &ST = static_cast<const X86Subtarget &>(TSI);
// Check if this processor supports any kind of fusion.
if (!(ST.hasBranchFusion() || ST.hasMacroFusion()))
return false;
const JumpKind BranchKind = classifySecond(SecondMI);
if (BranchKind == JumpKind::Invalid)
return false; // Second cannot be fused with anything.
if (FirstMI == nullptr)
return true; // We're only checking whether Second can be fused at all.
const FirstInstrKind TestKind = classifyFirst(*FirstMI);
if (ST.hasBranchFusion()) {
// Branch fusion can merge CMP and TEST with all conditional jumps.
return (TestKind == FirstInstrKind::Cmp ||
TestKind == FirstInstrKind::Test);
if (ST.hasMacroFusion()) {
// Macro Fusion rules are a bit more complex. See Agner Fog's
// Microarchitecture table 9.2 "Instruction Fusion".
switch (TestKind) {
case FirstInstrKind::Test:
case FirstInstrKind::And:
return true;
case FirstInstrKind::Cmp:
case FirstInstrKind::ALU:
return BranchKind == JumpKind::ELG || BranchKind == JumpKind::AB;
case FirstInstrKind::IncDec:
return BranchKind == JumpKind::ELG;
case FirstInstrKind::Invalid:
return false;
llvm_unreachable("unknown branch fusion type");
namespace llvm {
createX86MacroFusionDAGMutation () {
return createBranchMacroFusionDAGMutation(shouldScheduleAdjacent);
} // end namespace llvm