76 lines · cpp
1//===- X86MacroFusion.cpp - X86 Macro Fusion ------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9/// \file This file contains the X86 implementation of the DAG scheduling10/// mutation to pair instructions back to back.11//12//===----------------------------------------------------------------------===//13 14#include "X86MacroFusion.h"15#include "MCTargetDesc/X86BaseInfo.h"16#include "X86Subtarget.h"17#include "llvm/CodeGen/MacroFusion.h"18#include "llvm/CodeGen/ScheduleDAGMutation.h"19#include "llvm/CodeGen/TargetInstrInfo.h"20 21using namespace llvm;22 23static X86::FirstMacroFusionInstKind classifyFirst(const MachineInstr &MI) {24 return X86::classifyFirstOpcodeInMacroFusion(MI.getOpcode());25}26 27static X86::SecondMacroFusionInstKind classifySecond(const MachineInstr &MI) {28 X86::CondCode CC = X86::getCondFromBranch(MI);29 return X86::classifySecondCondCodeInMacroFusion(CC);30}31 32/// Check if the instr pair, FirstMI and SecondMI, should be fused33/// together. Given SecondMI, when FirstMI is unspecified, then check if34/// SecondMI may be part of a fused pair at all.35static bool shouldScheduleAdjacent(const TargetInstrInfo &TII,36 const TargetSubtargetInfo &TSI,37 const MachineInstr *FirstMI,38 const MachineInstr &SecondMI) {39 const X86Subtarget &ST = static_cast<const X86Subtarget &>(TSI);40 41 // Check if this processor supports any kind of fusion.42 if (!(ST.hasBranchFusion() || ST.hasMacroFusion()))43 return false;44 45 const X86::SecondMacroFusionInstKind BranchKind = classifySecond(SecondMI);46 47 if (BranchKind == X86::SecondMacroFusionInstKind::Invalid)48 return false; // Second cannot be fused with anything.49 50 if (FirstMI == nullptr)51 return true; // We're only checking whether Second can be fused at all.52 53 const X86::FirstMacroFusionInstKind TestKind = classifyFirst(*FirstMI);54 55 if (ST.hasBranchFusion()) {56 // Branch fusion can merge CMP and TEST with all conditional jumps.57 return (TestKind == X86::FirstMacroFusionInstKind::Cmp ||58 TestKind == X86::FirstMacroFusionInstKind::Test);59 }60 61 if (ST.hasMacroFusion()) {62 return X86::isMacroFused(TestKind, BranchKind);63 }64 65 llvm_unreachable("unknown fusion type");66}67 68namespace llvm {69 70std::unique_ptr<ScheduleDAGMutation> createX86MacroFusionDAGMutation() {71 return createMacroFusionDAGMutation(shouldScheduleAdjacent,72 /*BranchOnly=*/true);73}74 75} // end namespace llvm76