llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp

   1 //===- llvm/CodeGen/GlobalISel/InstructionSelector.cpp --------------------===//
   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
  10 /// This file implements the InstructionSelector class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
  15 #include "llvm/CodeGen/GlobalISel/Utils.h"
  16 #include "llvm/CodeGen/MachineInstr.h"
  17 #include "llvm/CodeGen/MachineOperand.h"
  18 #include "llvm/CodeGen/MachineRegisterInfo.h"
  19
  20 #define DEBUG_TYPE "instructionselector"
  21
  22 using namespace llvm;
  23
  24 InstructionSelector::MatcherState::MatcherState(unsigned MaxRenderers)
  25     : Renderers(MaxRenderers) {}
  26
  27 InstructionSelector::InstructionSelector() = default;
  28
  29 bool InstructionSelector::isOperandImmEqual(
  30     const MachineOperand &MO, int64_t Value,
  31     const MachineRegisterInfo &MRI) const {
  32   if (MO.isReg() && MO.getReg())
  33     if (auto VRegVal = getIConstantVRegValWithLookThrough(MO.getReg(), MRI))
  34       return VRegVal->Value.getSExtValue() == Value;
  35   return false;
  36 }
  37
  38 bool InstructionSelector::isBaseWithConstantOffset(
  39     const MachineOperand &Root, const MachineRegisterInfo &MRI) const {
  40   if (!Root.isReg())
  41     return false;
  42
  43   MachineInstr *RootI = MRI.getVRegDef(Root.getReg());
  44   if (RootI->getOpcode() != TargetOpcode::G_PTR_ADD)
  45     return false;
  46
  47   MachineOperand &RHS = RootI->getOperand(2);
  48   MachineInstr *RHSI = MRI.getVRegDef(RHS.getReg());
  49   if (RHSI->getOpcode() != TargetOpcode::G_CONSTANT)
  50     return false;
  51
  52   return true;
  53 }
  54
  55 bool InstructionSelector::isObviouslySafeToFold(MachineInstr &MI,
  56                                                 MachineInstr &IntoMI) const {
  57   // Immediate neighbours are already folded.
  58   if (MI.getParent() == IntoMI.getParent() &&
  59       std::next(MI.getIterator()) == IntoMI.getIterator())
  60     return true;
  61
  62   // Convergent instructions cannot be moved in the CFG.
  63   if (MI.isConvergent() && MI.getParent() != IntoMI.getParent())
  64     return false;
  65
  66   return !MI.mayLoadOrStore() && !MI.mayRaiseFPException() &&
  67          !MI.hasUnmodeledSideEffects() && MI.implicit_operands().empty();
  68 }