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 21 using namespace llvm; 22 23 static X86::FirstMacroFusionInstKind classifyFirst(const MachineInstr &MI) { 24 return X86::classifyFirstOpcodeInMacroFusion(MI.getOpcode()); 25 } 26 27 static 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. 35 static 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 68 namespace llvm { 69 70 std::unique_ptr<ScheduleDAGMutation> 71 createX86MacroFusionDAGMutation () { 72 return createBranchMacroFusionDAGMutation(shouldScheduleAdjacent); 73 } 74 75 } // end namespace llvm 76