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-exception
6//
7//===----------------------------------------------------------------------===//
8//
9/// \file This file contains the X86 implementation of the DAG scheduling
10/// 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(Opcode: 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 fused
33/// together. Given SecondMI, when FirstMI is unspecified, then check if
34/// 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 SDep *Dep) {
40 if (isNonDataDep(Dep))
41 return false;
42 const X86Subtarget &ST = static_cast<const X86Subtarget &>(TSI);
43
44 // Check if this processor supports any kind of fusion.
45 if (!(ST.hasBranchFusion() || ST.hasMacroFusion()))
46 return false;
47
48 const X86::SecondMacroFusionInstKind BranchKind = classifySecond(MI: SecondMI);
49
50 if (BranchKind == X86::SecondMacroFusionInstKind::Invalid)
51 return false; // Second cannot be fused with anything.
52
53 if (FirstMI == nullptr)
54 return true; // We're only checking whether Second can be fused at all.
55
56 const X86::FirstMacroFusionInstKind TestKind = classifyFirst(MI: *FirstMI);
57
58 if (ST.hasBranchFusion()) {
59 // Branch fusion can merge CMP and TEST with all conditional jumps.
60 return (TestKind == X86::FirstMacroFusionInstKind::Cmp ||
61 TestKind == X86::FirstMacroFusionInstKind::Test);
62 }
63
64 if (ST.hasMacroFusion()) {
65 return X86::isMacroFused(FirstKind: TestKind, SecondKind: BranchKind);
66 }
67
68 llvm_unreachable("unknown fusion type");
69}
70
71namespace llvm {
72
73std::unique_ptr<ScheduleDAGMutation> createX86MacroFusionDAGMutation() {
74 return createMacroFusionDAGMutation(Predicates: shouldScheduleAdjacent,
75 /*BranchOnly=*/true);
76}
77
78} // end namespace llvm
79