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//===- X86MacroFusion.cpp - X86 Macro Fusion ------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
/// \file This file contains the X86 implementation of the DAG scheduling
/// mutation to pair instructions back to back.
//
//===----------------------------------------------------------------------===//
#include "X86MacroFusion.h"
#include "MCTargetDesc/X86BaseInfo.h"
#include "X86Subtarget.h"
#include "llvm/CodeGen/MacroFusion.h"
#include "llvm/CodeGen/ScheduleDAGMutation.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
using namespace llvm;
static X86::FirstMacroFusionInstKind classifyFirst(const MachineInstr &MI) {
return X86::classifyFirstOpcodeInMacroFusion(MI.getOpcode());
}
static X86::SecondMacroFusionInstKind classifySecond(const MachineInstr &MI) {
X86::CondCode CC = X86::getCondFromBranch(MI);
return X86::classifySecondCondCodeInMacroFusion(CC);
}
/// 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 X86::SecondMacroFusionInstKind BranchKind = classifySecond(SecondMI);
if (BranchKind == X86::SecondMacroFusionInstKind::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 X86::FirstMacroFusionInstKind TestKind = classifyFirst(*FirstMI);
if (ST.hasBranchFusion()) {
// Branch fusion can merge CMP and TEST with all conditional jumps.
return (TestKind == X86::FirstMacroFusionInstKind::Cmp ||
TestKind == X86::FirstMacroFusionInstKind::Test);
}
if (ST.hasMacroFusion()) {
return X86::isMacroFused(TestKind, BranchKind);
}
llvm_unreachable("unknown fusion type");
}
namespace llvm {
std::unique_ptr<ScheduleDAGMutation>
createX86MacroFusionDAGMutation () {
return createBranchMacroFusionDAGMutation(shouldScheduleAdjacent);
}
} // end namespace llvm
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