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//===-- llvm/CodeGen/GlobalISel/CSEMIRBuilder.h --*- C++ -*-==//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// \file
/// This file implements a version of MachineIRBuilder which CSEs insts within
/// a MachineBasicBlock.
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
namespace llvm {
class GISelInstProfileBuilder;
/// Defines a builder that does CSE of MachineInstructions using GISelCSEInfo.
/// Eg usage.
/// GISelCSEInfo *Info =
/// &getAnalysis<GISelCSEAnalysisWrapperPass>().getCSEInfo(); CSEMIRBuilder
/// CB(Builder.getState()); CB.setCSEInfo(Info); auto A = CB.buildConstant(s32,
/// 42); auto B = CB.buildConstant(s32, 42); assert(A == B); unsigned CReg =
/// MRI.createGenericVirtualRegister(s32); auto C = CB.buildConstant(CReg, 42);
/// assert(C->getOpcode() == TargetOpcode::COPY);
/// Explicitly passing in a register would materialize a copy if possible.
/// CSEMIRBuilder also does trivial constant folding for binary ops.
class CSEMIRBuilder : public MachineIRBuilder {
/// Returns true if A dominates B (within the same basic block).
/// Both iterators must be in the same basic block.
// TODO: Another approach for checking dominance is having two iterators and
// making them go towards each other until they meet or reach begin/end. Which
// approach is better? Should this even change dynamically? For G_CONSTANTS
// most of which will be at the top of the BB, the top down approach would be
// a better choice. Does IRTranslator placing constants at the beginning still
// make sense? Should this change based on Opcode?
bool dominates(MachineBasicBlock::const_iterator A,
MachineBasicBlock::const_iterator B) const;
/// For given ID, find a machineinstr in the CSE Map. If found, check if it
/// dominates the current insertion point and if not, move it just before the
/// current insertion point and return it. If not found, return Null
/// MachineInstrBuilder.
MachineInstrBuilder getDominatingInstrForID(FoldingSetNodeID &ID,
void *&NodeInsertPos);
/// Simple check if we can CSE (we have the CSEInfo) or if this Opcode is
/// safe to CSE.
bool canPerformCSEForOpc(unsigned Opc) const;
void profileDstOp(const DstOp &Op, GISelInstProfileBuilder &B) const;
void profileDstOps(ArrayRef<DstOp> Ops, GISelInstProfileBuilder &B) const {
for (const DstOp &Op : Ops)
profileDstOp(Op, B);
void profileSrcOp(const SrcOp &Op, GISelInstProfileBuilder &B) const;
void profileSrcOps(ArrayRef<SrcOp> Ops, GISelInstProfileBuilder &B) const {
for (const SrcOp &Op : Ops)
profileSrcOp(Op, B);
void profileMBBOpcode(GISelInstProfileBuilder &B, unsigned Opc) const;
void profileEverything(unsigned Opc, ArrayRef<DstOp> DstOps,
ArrayRef<SrcOp> SrcOps, std::optional<unsigned> Flags,
GISelInstProfileBuilder &B) const;
// Takes a MachineInstrBuilder and inserts it into the CSEMap using the
// NodeInsertPos.
MachineInstrBuilder memoizeMI(MachineInstrBuilder MIB, void *NodeInsertPos);
// If we have can CSE an instruction, but still need to materialize to a VReg,
// we emit a copy from the CSE'd inst to the VReg.
MachineInstrBuilder generateCopiesIfRequired(ArrayRef<DstOp> DstOps,
MachineInstrBuilder &MIB);
// If we have can CSE an instruction, but still need to materialize to a VReg,
// check if we can generate copies. It's not possible to return a single MIB,
// while emitting copies to multiple vregs.
bool checkCopyToDefsPossible(ArrayRef<DstOp> DstOps);
// Pull in base class constructors.
using MachineIRBuilder::MachineIRBuilder;
// Unhide buildInstr
buildInstr(unsigned Opc, ArrayRef<DstOp> DstOps, ArrayRef<SrcOp> SrcOps,
std::optional<unsigned> Flag = std::nullopt) override;
// Bring in the other overload from the base class.
using MachineIRBuilder::buildConstant;
MachineInstrBuilder buildConstant(const DstOp &Res,
const ConstantInt &Val) override;
// Bring in the other overload from the base class.
using MachineIRBuilder::buildFConstant;
MachineInstrBuilder buildFConstant(const DstOp &Res,
const ConstantFP &Val) override;
} // namespace llvm