121 lines
4.1 KiB
C++
121 lines
4.1 KiB
C++
//===-- SnippetRepetitor.cpp ------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include <array>
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#include <string>
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#include "SnippetRepetitor.h"
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#include "Target.h"
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#include "llvm/CodeGen/TargetInstrInfo.h"
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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namespace llvm {
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namespace exegesis {
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namespace {
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class DuplicateSnippetRepetitor : public SnippetRepetitor {
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public:
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using SnippetRepetitor::SnippetRepetitor;
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// Repeats the snippet until there are at least MinInstructions in the
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// resulting code.
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FillFunction Repeat(ArrayRef<MCInst> Instructions,
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unsigned MinInstructions) const override {
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return [Instructions, MinInstructions](FunctionFiller &Filler) {
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auto Entry = Filler.getEntry();
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if (!Instructions.empty()) {
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// Add the whole snippet at least once.
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Entry.addInstructions(Instructions);
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for (unsigned I = Instructions.size(); I < MinInstructions; ++I) {
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Entry.addInstruction(Instructions[I % Instructions.size()]);
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}
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}
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Entry.addReturn();
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};
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}
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BitVector getReservedRegs() const override {
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// We're using no additional registers.
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return State.getRATC().emptyRegisters();
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}
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};
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class LoopSnippetRepetitor : public SnippetRepetitor {
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public:
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explicit LoopSnippetRepetitor(const LLVMState &State)
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: SnippetRepetitor(State),
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LoopCounter(State.getExegesisTarget().getLoopCounterRegister(
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State.getTargetMachine().getTargetTriple())) {}
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// Loop over the snippet ceil(MinInstructions / Instructions.Size()) times.
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FillFunction Repeat(ArrayRef<MCInst> Instructions,
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unsigned MinInstructions) const override {
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return [this, Instructions, MinInstructions](FunctionFiller &Filler) {
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const auto &ET = State.getExegesisTarget();
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auto Entry = Filler.getEntry();
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auto Loop = Filler.addBasicBlock();
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auto Exit = Filler.addBasicBlock();
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// Set loop counter to the right value:
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const APInt LoopCount(32, (MinInstructions + Instructions.size() - 1) /
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Instructions.size());
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for (const MCInst &Inst :
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ET.setRegTo(State.getSubtargetInfo(), LoopCounter, LoopCount))
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Entry.addInstruction(Inst);
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// Set up the loop basic block.
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Entry.MBB->addSuccessor(Loop.MBB, BranchProbability::getOne());
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Loop.MBB->addSuccessor(Loop.MBB, BranchProbability::getOne());
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// The live ins are: the loop counter, the registers that were setup by
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// the entry block, and entry block live ins.
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Loop.MBB->addLiveIn(LoopCounter);
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for (unsigned Reg : Filler.getRegistersSetUp())
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Loop.MBB->addLiveIn(Reg);
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for (const auto &LiveIn : Entry.MBB->liveins())
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Loop.MBB->addLiveIn(LiveIn);
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Loop.addInstructions(Instructions);
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ET.decrementLoopCounterAndJump(*Loop.MBB, *Loop.MBB,
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State.getInstrInfo());
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// Set up the exit basic block.
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Loop.MBB->addSuccessor(Exit.MBB, BranchProbability::getZero());
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Exit.addReturn();
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};
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}
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BitVector getReservedRegs() const override {
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// We're using a single loop counter, but we have to reserve all aliasing
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// registers.
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return State.getRATC().getRegister(LoopCounter).aliasedBits();
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}
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private:
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const unsigned LoopCounter;
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};
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} // namespace
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SnippetRepetitor::~SnippetRepetitor() {}
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std::unique_ptr<const SnippetRepetitor>
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SnippetRepetitor::Create(InstructionBenchmark::RepetitionModeE Mode,
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const LLVMState &State) {
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switch (Mode) {
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case InstructionBenchmark::Duplicate:
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return std::make_unique<DuplicateSnippetRepetitor>(State);
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case InstructionBenchmark::Loop:
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return std::make_unique<LoopSnippetRepetitor>(State);
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case InstructionBenchmark::AggregateMin:
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break;
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}
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llvm_unreachable("Unknown RepetitionModeE enum");
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}
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} // namespace exegesis
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} // namespace llvm
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