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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
88 lines
3.4 KiB
C++
88 lines
3.4 KiB
C++
//===- llvm/CodeGen/AntiDepBreaker.h - Anti-Dependence Breaking -*- 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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//
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// This file implements the AntiDepBreaker class, which implements
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// anti-dependence breaking heuristics for post-register-allocation scheduling.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_CODEGEN_ANTIDEPBREAKER_H
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#define LLVM_LIB_CODEGEN_ANTIDEPBREAKER_H
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#include "llvm/ADT/iterator_range.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineOperand.h"
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#include "llvm/CodeGen/ScheduleDAG.h"
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#include "llvm/Support/Compiler.h"
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#include <cassert>
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#include <utility>
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#include <vector>
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namespace llvm {
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/// This class works in conjunction with the post-RA scheduler to rename
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/// registers to break register anti-dependencies (WAR hazards).
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class LLVM_LIBRARY_VISIBILITY AntiDepBreaker {
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public:
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using DbgValueVector =
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std::vector<std::pair<MachineInstr *, MachineInstr *>>;
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virtual ~AntiDepBreaker();
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/// Initialize anti-dep breaking for a new basic block.
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virtual void StartBlock(MachineBasicBlock *BB) = 0;
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/// Identifiy anti-dependencies within a basic-block region and break them by
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/// renaming registers. Return the number of anti-dependencies broken.
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virtual unsigned BreakAntiDependencies(const std::vector<SUnit> &SUnits,
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MachineBasicBlock::iterator Begin,
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MachineBasicBlock::iterator End,
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unsigned InsertPosIndex,
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DbgValueVector &DbgValues) = 0;
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/// Update liveness information to account for the current
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/// instruction, which will not be scheduled.
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virtual void Observe(MachineInstr &MI, unsigned Count,
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unsigned InsertPosIndex) = 0;
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/// Finish anti-dep breaking for a basic block.
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virtual void FinishBlock() = 0;
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/// Update DBG_VALUE if dependency breaker is updating
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/// other machine instruction to use NewReg.
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void UpdateDbgValue(MachineInstr &MI, unsigned OldReg, unsigned NewReg) {
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assert(MI.isDebugValue() && "MI is not DBG_VALUE!");
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if (MI.getOperand(0).isReg() && MI.getOperand(0).getReg() == OldReg)
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MI.getOperand(0).setReg(NewReg);
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}
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/// Update all DBG_VALUE instructions that may be affected by the dependency
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/// breaker's update of ParentMI to use NewReg.
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void UpdateDbgValues(const DbgValueVector &DbgValues, MachineInstr *ParentMI,
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unsigned OldReg, unsigned NewReg) {
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// The following code is dependent on the order in which the DbgValues are
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// constructed in ScheduleDAGInstrs::buildSchedGraph.
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MachineInstr *PrevDbgMI = nullptr;
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for (const auto &DV : make_range(DbgValues.crbegin(), DbgValues.crend())) {
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MachineInstr *PrevMI = DV.second;
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if ((PrevMI == ParentMI) || (PrevMI == PrevDbgMI)) {
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MachineInstr *DbgMI = DV.first;
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UpdateDbgValue(*DbgMI, OldReg, NewReg);
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PrevDbgMI = DbgMI;
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} else if (PrevDbgMI) {
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break; // If no match and already found a DBG_VALUE, we're done.
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}
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}
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}
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};
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} // end namespace llvm
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#endif // LLVM_LIB_CODEGEN_ANTIDEPBREAKER_H
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