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f469a1f4e3
G_INTTOPTR can prevent the localizer from moving G_CONSTANTs, but since it's essentially a side effect free cast instruction we can remat both instructions. This patch changes the localizer to enable localization of the chains by iterating over the entry block instructions in reverse order. That way, uses will localized first, and then the defs are free to be localized as well. This also changes the previous SmallPtrSet of localized instructions to use a SetVector instead. We're dealing with pointers and need deterministic iteration order. Overall, this change improves ARM64 -O0 CTMark code size by around 0.7% geomean. Differential Revision: https://reviews.llvm.org/D63630 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@364001 91177308-0d34-0410-b5e6-96231b3b80d8
93 lines
3.5 KiB
C++
93 lines
3.5 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/ADT/SetVector.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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class TargetTransformInfo;
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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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/// TTI used for getting remat costs for instructions.
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TargetTransformInfo *TTI;
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/// Check whether or not \p MI needs to be moved close to its uses.
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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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typedef SmallSetVector<MachineInstr *, 32> LocalizedSetVecT;
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/// Do inter-block localization from the entry block.
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bool localizeInterBlock(MachineFunction &MF,
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LocalizedSetVecT &LocalizedInstrs);
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/// Do intra-block localization of already localized instructions.
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bool localizeIntraBlock(LocalizedSetVecT &LocalizedInstrs);
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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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