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llvm-mirror/lib/Target/AArch64/AArch64.h
Amara Emerson a5ff88d2db [AArch64][GlobalISel] Introduce a new post-isel optimization pass.
There are two optimizations here:

1. Consider the following code:
 FCMPSrr %0, %1, implicit-def $nzcv
 %sel1:gpr32 = CSELWr %_, %_, 12, implicit $nzcv
 %sub:gpr32 = SUBSWrr %_, %_, implicit-def $nzcv
 FCMPSrr %0, %1, implicit-def $nzcv
 %sel2:gpr32 = CSELWr %_, %_, 12, implicit $nzcv
This kind of code where we have 2 FCMPs each feeding a CSEL can happen
when we have a single IR fcmp being used by two selects. During selection,
to ensure that there can be no clobbering of nzcv between the fcmp and the
csel, we have to generate an fcmp immediately before each csel is
selected.

However, often we can essentially CSE these together later in MachineCSE.
This doesn't work though if there are unrelated flag-setting instructions
in between the two FCMPs. In this case, the SUBS defines NZCV
but it doesn't have any users, being overwritten by the second FCMP.

Our solution here is to try to convert flag setting operations between
a interval of identical FCMPs, so that CSE will be able to eliminate one.

2. SelectionDAG imported patterns for arithmetic ops currently select the
flag-setting ops for CSE reasons, and add the implicit-def $nzcv operand
to those instructions. However if those impdef operands are not marked as
dead, the peephole optimizations are not able to optimize them into non-flag
setting variants. The optimization here is to find these dead imp-defs and
mark them as such.

This pass is only enabled when optimizations are enabled.

Differential Revision: https://reviews.llvm.org/D89415
2020-10-23 10:18:36 -07:00

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//==-- AArch64.h - Top-level interface for AArch64 --------------*- 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
//
//===----------------------------------------------------------------------===//
//
// This file contains the entry points for global functions defined in the LLVM
// AArch64 back-end.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_TARGET_AARCH64_AARCH64_H
#define LLVM_LIB_TARGET_AARCH64_AARCH64_H
#include "MCTargetDesc/AArch64MCTargetDesc.h"
#include "Utils/AArch64BaseInfo.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Target/TargetMachine.h"
namespace llvm {
class AArch64RegisterBankInfo;
class AArch64Subtarget;
class AArch64TargetMachine;
class FunctionPass;
class InstructionSelector;
class MachineFunctionPass;
FunctionPass *createAArch64DeadRegisterDefinitions();
FunctionPass *createAArch64RedundantCopyEliminationPass();
FunctionPass *createAArch64CondBrTuning();
FunctionPass *createAArch64CompressJumpTablesPass();
FunctionPass *createAArch64ConditionalCompares();
FunctionPass *createAArch64AdvSIMDScalar();
FunctionPass *createAArch64ISelDag(AArch64TargetMachine &TM,
CodeGenOpt::Level OptLevel);
FunctionPass *createAArch64StorePairSuppressPass();
FunctionPass *createAArch64ExpandPseudoPass();
FunctionPass *createAArch64SLSHardeningPass();
FunctionPass *createAArch64IndirectThunks();
FunctionPass *createAArch64SpeculationHardeningPass();
FunctionPass *createAArch64LoadStoreOptimizationPass();
FunctionPass *createAArch64SIMDInstrOptPass();
ModulePass *createAArch64PromoteConstantPass();
FunctionPass *createAArch64ConditionOptimizerPass();
FunctionPass *createAArch64A57FPLoadBalancing();
FunctionPass *createAArch64A53Fix835769();
FunctionPass *createFalkorHWPFFixPass();
FunctionPass *createFalkorMarkStridedAccessesPass();
FunctionPass *createAArch64BranchTargetsPass();
FunctionPass *createAArch64CleanupLocalDynamicTLSPass();
FunctionPass *createAArch64CollectLOHPass();
ModulePass *createSVEIntrinsicOptsPass();
InstructionSelector *
createAArch64InstructionSelector(const AArch64TargetMachine &,
AArch64Subtarget &, AArch64RegisterBankInfo &);
FunctionPass *createAArch64PreLegalizerCombiner(bool IsOptNone);
FunctionPass *createAArch64PostLegalizerCombiner(bool IsOptNone);
FunctionPass *createAArch64PostLegalizerLowering();
FunctionPass *createAArch64PostSelectOptimize();
FunctionPass *createAArch64StackTaggingPass(bool IsOptNone);
FunctionPass *createAArch64StackTaggingPreRAPass();
void initializeAArch64A53Fix835769Pass(PassRegistry&);
void initializeAArch64A57FPLoadBalancingPass(PassRegistry&);
void initializeAArch64AdvSIMDScalarPass(PassRegistry&);
void initializeAArch64BranchTargetsPass(PassRegistry&);
void initializeAArch64CollectLOHPass(PassRegistry&);
void initializeAArch64CondBrTuningPass(PassRegistry &);
void initializeAArch64CompressJumpTablesPass(PassRegistry&);
void initializeAArch64ConditionalComparesPass(PassRegistry&);
void initializeAArch64ConditionOptimizerPass(PassRegistry&);
void initializeAArch64DeadRegisterDefinitionsPass(PassRegistry&);
void initializeAArch64ExpandPseudoPass(PassRegistry&);
void initializeAArch64SLSHardeningPass(PassRegistry&);
void initializeAArch64SpeculationHardeningPass(PassRegistry&);
void initializeAArch64LoadStoreOptPass(PassRegistry&);
void initializeAArch64SIMDInstrOptPass(PassRegistry&);
void initializeAArch64PreLegalizerCombinerPass(PassRegistry&);
void initializeAArch64PostLegalizerCombinerPass(PassRegistry &);
void initializeAArch64PostLegalizerLoweringPass(PassRegistry &);
void initializeAArch64PostSelectOptimizePass(PassRegistry &);
void initializeAArch64PromoteConstantPass(PassRegistry&);
void initializeAArch64RedundantCopyEliminationPass(PassRegistry&);
void initializeAArch64StorePairSuppressPass(PassRegistry&);
void initializeFalkorHWPFFixPass(PassRegistry&);
void initializeFalkorMarkStridedAccessesLegacyPass(PassRegistry&);
void initializeLDTLSCleanupPass(PassRegistry&);
void initializeSVEIntrinsicOptsPass(PassRegistry&);
void initializeAArch64StackTaggingPass(PassRegistry&);
void initializeAArch64StackTaggingPreRAPass(PassRegistry&);
} // end namespace llvm
#endif