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/TargetInstrInfo.h" 19 20 using namespace llvm; 21 22 static X86::FirstMacroFusionInstKind classifyFirst(const MachineInstr &MI) { 23 return X86::classifyFirstOpcodeInMacroFusion(MI.getOpcode()); 24 } 25 26 static X86::SecondMacroFusionInstKind classifySecond(const MachineInstr &MI) { 27 X86::CondCode CC = X86::getCondFromBranch(MI); 28 return X86::classifySecondCondCodeInMacroFusion(CC); 29 } 30 31 /// Check if the instr pair, FirstMI and SecondMI, should be fused 32 /// together. Given SecondMI, when FirstMI is unspecified, then check if 33 /// SecondMI may be part of a fused pair at all. 34 static bool shouldScheduleAdjacent(const TargetInstrInfo &TII, 35 const TargetSubtargetInfo &TSI, 36 const MachineInstr *FirstMI, 37 const MachineInstr &SecondMI) { 38 const X86Subtarget &ST = static_cast<const X86Subtarget &>(TSI); 39 40 // Check if this processor supports any kind of fusion. 41 if (!(ST.hasBranchFusion() || ST.hasMacroFusion())) 42 return false; 43 44 const X86::SecondMacroFusionInstKind BranchKind = classifySecond(SecondMI); 45 46 if (BranchKind == X86::SecondMacroFusionInstKind::Invalid) 47 return false; // Second cannot be fused with anything. 48 49 if (FirstMI == nullptr) 50 return true; // We're only checking whether Second can be fused at all. 51 52 const X86::FirstMacroFusionInstKind TestKind = classifyFirst(*FirstMI); 53 54 if (ST.hasBranchFusion()) { 55 // Branch fusion can merge CMP and TEST with all conditional jumps. 56 return (TestKind == X86::FirstMacroFusionInstKind::Cmp || 57 TestKind == X86::FirstMacroFusionInstKind::Test); 58 } 59 60 if (ST.hasMacroFusion()) { 61 return X86::isMacroFused(TestKind, BranchKind); 62 } 63 64 llvm_unreachable("unknown fusion type"); 65 } 66 67 namespace llvm { 68 69 std::unique_ptr<ScheduleDAGMutation> 70 createX86MacroFusionDAGMutation () { 71 return createBranchMacroFusionDAGMutation(shouldScheduleAdjacent); 72 } 73 74 } // end namespace llvm 75