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80 lines
3.0 KiB
C++
80 lines
3.0 KiB
C++
//== llvm/CodeGen/GlobalISel/Localizer.h - Localizer -------------*- 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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/// \file This file describes the interface of the Localizer pass.
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/// This pass moves/duplicates constant-like instructions close to their uses.
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/// Its primarily goal is to workaround the deficiencies of the fast register
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/// allocator.
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/// With GlobalISel constants are all materialized in the entry block of
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/// a function. However, the fast allocator cannot rematerialize constants and
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/// has a lot more live-ranges to deal with and will most likely end up
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/// spilling a lot.
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/// By pushing the constants close to their use, we only create small
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/// live-ranges.
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_GLOBALISEL_LOCALIZER_H
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#define LLVM_CODEGEN_GLOBALISEL_LOCALIZER_H
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#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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namespace llvm {
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// Forward declarations.
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class MachineRegisterInfo;
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/// This pass implements the localization mechanism described at the
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/// top of this file. One specificity of the implementation is that
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/// it will materialize one and only one instance of a constant per
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/// basic block, thus enabling reuse of that constant within that block.
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/// Moreover, it only materializes constants in blocks where they
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/// are used. PHI uses are considered happening at the end of the
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/// related predecessor.
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class Localizer : public MachineFunctionPass {
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public:
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static char ID;
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private:
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/// MRI contains all the register class/bank information that this
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/// pass uses and updates.
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MachineRegisterInfo *MRI;
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/// Check whether or not \p MI needs to be moved close to its uses.
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static bool shouldLocalize(const MachineInstr &MI);
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/// Check if \p MOUse is used in the same basic block as \p Def.
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/// If the use is in the same block, we say it is local.
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/// When the use is not local, \p InsertMBB will contain the basic
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/// block when to insert \p Def to have a local use.
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static bool isLocalUse(MachineOperand &MOUse, const MachineInstr &Def,
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MachineBasicBlock *&InsertMBB);
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/// Initialize the field members using \p MF.
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void init(MachineFunction &MF);
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public:
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Localizer();
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StringRef getPassName() const override { return "Localizer"; }
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MachineFunctionProperties getRequiredProperties() const override {
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return MachineFunctionProperties()
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.set(MachineFunctionProperties::Property::IsSSA)
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.set(MachineFunctionProperties::Property::Legalized)
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.set(MachineFunctionProperties::Property::RegBankSelected);
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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bool runOnMachineFunction(MachineFunction &MF) override;
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};
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} // End namespace llvm.
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#endif
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