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//===-- llvm/CodeGen/GlobalISel/CSEMIRBuilder.cpp - MIBuilder--*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements the CSEMIRBuilder class which CSEs as it builds
/// instructions.
//===----------------------------------------------------------------------===//
//
#include "llvm/CodeGen/GlobalISel/CSEMIRBuilder.h"
#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
using namespace llvm;
bool CSEMIRBuilder::dominates(MachineBasicBlock::const_iterator A,
MachineBasicBlock::const_iterator B) const {
auto MBBEnd = getMBB().end();
if (B == MBBEnd)
return true;
assert(A->getParent() == B->getParent() &&
"Iterators should be in same block");
const MachineBasicBlock *BBA = A->getParent();
MachineBasicBlock::const_iterator I = BBA->begin();
for (; &*I != A && &*I != B; ++I)
;
return &*I == A;
}
MachineInstrBuilder
CSEMIRBuilder::getDominatingInstrForID(FoldingSetNodeID &ID,
void *&NodeInsertPos) {
GISelCSEInfo *CSEInfo = getCSEInfo();
assert(CSEInfo && "Can't get here without setting CSEInfo");
MachineBasicBlock *CurMBB = &getMBB();
MachineInstr *MI =
CSEInfo->getMachineInstrIfExists(ID, CurMBB, NodeInsertPos);
if (MI) {
CSEInfo->countOpcodeHit(MI->getOpcode());
auto CurrPos = getInsertPt();
if (!dominates(MI, CurrPos))
CurMBB->splice(CurrPos, CurMBB, MI);
return MachineInstrBuilder(getMF(), MI);
}
return MachineInstrBuilder();
}
bool CSEMIRBuilder::canPerformCSEForOpc(unsigned Opc) const {
const GISelCSEInfo *CSEInfo = getCSEInfo();
if (!CSEInfo || !CSEInfo->shouldCSE(Opc))
return false;
return true;
}
void CSEMIRBuilder::profileDstOp(const DstOp &Op,
GISelInstProfileBuilder &B) const {
switch (Op.getDstOpKind()) {
case DstOp::DstType::Ty_RC:
B.addNodeIDRegType(Op.getRegClass());
break;
default:
B.addNodeIDRegType(Op.getLLTTy(*getMRI()));
break;
}
}
void CSEMIRBuilder::profileSrcOp(const SrcOp &Op,
GISelInstProfileBuilder &B) const {
switch (Op.getSrcOpKind()) {
case SrcOp::SrcType::Ty_Predicate:
B.addNodeIDImmediate(static_cast<int64_t>(Op.getPredicate()));
break;
default:
B.addNodeIDRegType(Op.getReg());
break;
}
}
void CSEMIRBuilder::profileMBBOpcode(GISelInstProfileBuilder &B,
unsigned Opc) const {
// First add the MBB (Local CSE).
B.addNodeIDMBB(&getMBB());
// Then add the opcode.
B.addNodeIDOpcode(Opc);
}
void CSEMIRBuilder::profileEverything(unsigned Opc, ArrayRef<DstOp> DstOps,
ArrayRef<SrcOp> SrcOps,
Optional<unsigned> Flags,
GISelInstProfileBuilder &B) const {
profileMBBOpcode(B, Opc);
// Then add the DstOps.
profileDstOps(DstOps, B);
// Then add the SrcOps.
profileSrcOps(SrcOps, B);
// Add Flags if passed in.
if (Flags)
B.addNodeIDFlag(*Flags);
}
MachineInstrBuilder CSEMIRBuilder::memoizeMI(MachineInstrBuilder MIB,
void *NodeInsertPos) {
assert(canPerformCSEForOpc(MIB->getOpcode()) &&
"Attempting to CSE illegal op");
MachineInstr *MIBInstr = MIB;
getCSEInfo()->insertInstr(MIBInstr, NodeInsertPos);
return MIB;
}
bool CSEMIRBuilder::checkCopyToDefsPossible(ArrayRef<DstOp> DstOps) {
if (DstOps.size() == 1)
return true; // always possible to emit copy to just 1 vreg.
return std::all_of(DstOps.begin(), DstOps.end(), [](const DstOp &Op) {
DstOp::DstType DT = Op.getDstOpKind();
return DT == DstOp::DstType::Ty_LLT || DT == DstOp::DstType::Ty_RC;
});
}
MachineInstrBuilder
CSEMIRBuilder::generateCopiesIfRequired(ArrayRef<DstOp> DstOps,
MachineInstrBuilder &MIB) {
assert(checkCopyToDefsPossible(DstOps) &&
"Impossible return a single MIB with copies to multiple defs");
if (DstOps.size() == 1) {
const DstOp &Op = DstOps[0];
if (Op.getDstOpKind() == DstOp::DstType::Ty_Reg)
return buildCopy(Op.getReg(), MIB->getOperand(0).getReg());
}
return MIB;
}
MachineInstrBuilder CSEMIRBuilder::buildInstr(unsigned Opc,
ArrayRef<DstOp> DstOps,
ArrayRef<SrcOp> SrcOps,
Optional<unsigned> Flag) {
switch (Opc) {
default:
break;
case TargetOpcode::G_ADD:
case TargetOpcode::G_AND:
case TargetOpcode::G_ASHR:
case TargetOpcode::G_LSHR:
case TargetOpcode::G_MUL:
case TargetOpcode::G_OR:
case TargetOpcode::G_SHL:
case TargetOpcode::G_SUB:
case TargetOpcode::G_XOR:
case TargetOpcode::G_UDIV:
case TargetOpcode::G_SDIV:
case TargetOpcode::G_UREM:
case TargetOpcode::G_SREM: {
// Try to constant fold these.
assert(SrcOps.size() == 2 && "Invalid sources");
assert(DstOps.size() == 1 && "Invalid dsts");
if (Optional<APInt> Cst = ConstantFoldBinOp(Opc, SrcOps[0].getReg(),
SrcOps[1].getReg(), *getMRI()))
return buildConstant(DstOps[0], Cst->getSExtValue());
break;
}
}
bool CanCopy = checkCopyToDefsPossible(DstOps);
if (!canPerformCSEForOpc(Opc))
return MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flag);
// If we can CSE this instruction, but involves generating copies to multiple
// regs, give up. This frequently happens to UNMERGEs.
if (!CanCopy) {
auto MIB = MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flag);
// CSEInfo would have tracked this instruction. Remove it from the temporary
// insts.
getCSEInfo()->handleRemoveInst(&*MIB);
return MIB;
}
FoldingSetNodeID ID;
GISelInstProfileBuilder ProfBuilder(ID, *getMRI());
void *InsertPos = nullptr;
profileEverything(Opc, DstOps, SrcOps, Flag, ProfBuilder);
MachineInstrBuilder MIB = getDominatingInstrForID(ID, InsertPos);
if (MIB) {
// Handle generating copies here.
return generateCopiesIfRequired(DstOps, MIB);
}
// This instruction does not exist in the CSEInfo. Build it and CSE it.
MachineInstrBuilder NewMIB =
MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flag);
return memoizeMI(NewMIB, InsertPos);
}
MachineInstrBuilder CSEMIRBuilder::buildConstant(const DstOp &Res,
const ConstantInt &Val) {
constexpr unsigned Opc = TargetOpcode::G_CONSTANT;
if (!canPerformCSEForOpc(Opc))
return MachineIRBuilder::buildConstant(Res, Val);
// For vectors, CSE the element only for now.
LLT Ty = Res.getLLTTy(*getMRI());
if (Ty.isVector())
return buildSplatVector(Res, buildConstant(Ty.getElementType(), Val));
FoldingSetNodeID ID;
GISelInstProfileBuilder ProfBuilder(ID, *getMRI());
void *InsertPos = nullptr;
profileMBBOpcode(ProfBuilder, Opc);
profileDstOp(Res, ProfBuilder);
ProfBuilder.addNodeIDMachineOperand(MachineOperand::CreateCImm(&Val));
MachineInstrBuilder MIB = getDominatingInstrForID(ID, InsertPos);
if (MIB) {
// Handle generating copies here.
return generateCopiesIfRequired({Res}, MIB);
}
MachineInstrBuilder NewMIB = MachineIRBuilder::buildConstant(Res, Val);
return memoizeMI(NewMIB, InsertPos);
}
MachineInstrBuilder CSEMIRBuilder::buildFConstant(const DstOp &Res,
const ConstantFP &Val) {
constexpr unsigned Opc = TargetOpcode::G_FCONSTANT;
if (!canPerformCSEForOpc(Opc))
return MachineIRBuilder::buildFConstant(Res, Val);
// For vectors, CSE the element only for now.
LLT Ty = Res.getLLTTy(*getMRI());
if (Ty.isVector())
return buildSplatVector(Res, buildFConstant(Ty.getElementType(), Val));
FoldingSetNodeID ID;
GISelInstProfileBuilder ProfBuilder(ID, *getMRI());
void *InsertPos = nullptr;
profileMBBOpcode(ProfBuilder, Opc);
profileDstOp(Res, ProfBuilder);
ProfBuilder.addNodeIDMachineOperand(MachineOperand::CreateFPImm(&Val));
MachineInstrBuilder MIB = getDominatingInstrForID(ID, InsertPos);
if (MIB) {
// Handle generating copies here.
return generateCopiesIfRequired({Res}, MIB);
}
MachineInstrBuilder NewMIB = MachineIRBuilder::buildFConstant(Res, Val);
return memoizeMI(NewMIB, InsertPos);
}
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