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llvm-mirror/lib/Target/ARM/ARMTargetMachine.cpp
David Green 1643bee451 [Scheduling][ARM] Consistently enable PostRA Machine scheduling 
In the ARM backend, for historical reasons we have only some targets
using Machine Scheduling. The rest use the old list scheduler as they
are using itinaries and the list scheduler seems to produce better code
(and not crash running out of register on v6m codes). So whether to use
the MIScheduler or not is checked at runtime from the subtarget
features.

This is fine, except for post-ra scheduling. Whether to use the old
post-ra list scheduler or the post-ra machine schedule is decided as the
pass manager is set up, in arms case from a newly constructed subtarget.
Under some situations, like LTO, this won't include the correct cpu so
can pick the wrong option. This can have a surprising effect on
performance.

To fix that, this patch overrides targetSchedulesPostRAScheduling and
addPreSched2 in the ARM backend, adding _both_ post-ra schedulers and
picking at runtime which to execute. To pick between the two I've had to
add a enablePostRAMachineScheduler() method that normally returns
enableMachineScheduler() && enablePostRAScheduler(), which can be
overridden to enable just one of PostRAMachineScheduler vs
PostRAScheduler.

Thanks to David Penry for the identifying this problem.

Differential Revision: https://reviews.llvm.org/D69775
2019-11-05 10:44:55 +00:00

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//===-- ARMTargetMachine.cpp - Define TargetMachine for ARM ---------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//
#include "ARMTargetMachine.h"
#include "ARM.h"
#include "ARMMacroFusion.h"
#include "ARMSubtarget.h"
#include "ARMTargetObjectFile.h"
#include "ARMTargetTransformInfo.h"
#include "MCTargetDesc/ARMMCTargetDesc.h"
#include "TargetInfo/ARMTargetInfo.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/CodeGen/ExecutionDomainFix.h"
#include "llvm/CodeGen/GlobalISel/CallLowering.h"
#include "llvm/CodeGen/GlobalISel/IRTranslator.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
#include "llvm/CodeGen/GlobalISel/Legalizer.h"
#include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
#include "llvm/CodeGen/GlobalISel/RegBankSelect.h"
#include "llvm/CodeGen/GlobalISel/RegisterBankInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/Pass.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TargetParser.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Transforms/CFGuard.h"
#include "llvm/Transforms/Scalar.h"
#include <cassert>
#include <memory>
#include <string>
using namespace llvm;
static cl::opt<bool>
DisableA15SDOptimization("disable-a15-sd-optimization", cl::Hidden,
cl::desc("Inhibit optimization of S->D register accesses on A15"),
cl::init(false));
static cl::opt<bool>
EnableAtomicTidy("arm-atomic-cfg-tidy", cl::Hidden,
cl::desc("Run SimplifyCFG after expanding atomic operations"
" to make use of cmpxchg flow-based information"),
cl::init(true));
static cl::opt<bool>
EnableARMLoadStoreOpt("arm-load-store-opt", cl::Hidden,
cl::desc("Enable ARM load/store optimization pass"),
cl::init(true));
// FIXME: Unify control over GlobalMerge.
static cl::opt<cl::boolOrDefault>
EnableGlobalMerge("arm-global-merge", cl::Hidden,
cl::desc("Enable the global merge pass"));
namespace llvm {
void initializeARMExecutionDomainFixPass(PassRegistry&);
}
extern "C" void LLVMInitializeARMTarget() {
// Register the target.
RegisterTargetMachine<ARMLETargetMachine> X(getTheARMLETarget());
RegisterTargetMachine<ARMLETargetMachine> A(getTheThumbLETarget());
RegisterTargetMachine<ARMBETargetMachine> Y(getTheARMBETarget());
RegisterTargetMachine<ARMBETargetMachine> B(getTheThumbBETarget());
PassRegistry &Registry = *PassRegistry::getPassRegistry();
initializeGlobalISel(Registry);
initializeARMLoadStoreOptPass(Registry);
initializeARMPreAllocLoadStoreOptPass(Registry);
initializeARMParallelDSPPass(Registry);
initializeARMCodeGenPreparePass(Registry);
initializeARMConstantIslandsPass(Registry);
initializeARMExecutionDomainFixPass(Registry);
initializeARMExpandPseudoPass(Registry);
initializeThumb2SizeReducePass(Registry);
initializeMVEVPTBlockPass(Registry);
initializeMVETailPredicationPass(Registry);
initializeARMLowOverheadLoopsPass(Registry);
}
static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
if (TT.isOSBinFormatMachO())
return std::make_unique<TargetLoweringObjectFileMachO>();
if (TT.isOSWindows())
return std::make_unique<TargetLoweringObjectFileCOFF>();
return std::make_unique<ARMElfTargetObjectFile>();
}
static ARMBaseTargetMachine::ARMABI
computeTargetABI(const Triple &TT, StringRef CPU,
const TargetOptions &Options) {
StringRef ABIName = Options.MCOptions.getABIName();
if (ABIName.empty())
ABIName = ARM::computeDefaultTargetABI(TT, CPU);
if (ABIName == "aapcs16")
return ARMBaseTargetMachine::ARM_ABI_AAPCS16;
else if (ABIName.startswith("aapcs"))
return ARMBaseTargetMachine::ARM_ABI_AAPCS;
else if (ABIName.startswith("apcs"))
return ARMBaseTargetMachine::ARM_ABI_APCS;
llvm_unreachable("Unhandled/unknown ABI Name!");
return ARMBaseTargetMachine::ARM_ABI_UNKNOWN;
}
static std::string computeDataLayout(const Triple &TT, StringRef CPU,
const TargetOptions &Options,
bool isLittle) {
auto ABI = computeTargetABI(TT, CPU, Options);
std::string Ret;
if (isLittle)
// Little endian.
Ret += "e";
else
// Big endian.
Ret += "E";
Ret += DataLayout::getManglingComponent(TT);
// Pointers are 32 bits and aligned to 32 bits.
Ret += "-p:32:32";
// Function pointers are aligned to 8 bits (because the LSB stores the
// ARM/Thumb state).
Ret += "-Fi8";
// ABIs other than APCS have 64 bit integers with natural alignment.
if (ABI != ARMBaseTargetMachine::ARM_ABI_APCS)
Ret += "-i64:64";
// We have 64 bits floats. The APCS ABI requires them to be aligned to 32
// bits, others to 64 bits. We always try to align to 64 bits.
if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
Ret += "-f64:32:64";
// We have 128 and 64 bit vectors. The APCS ABI aligns them to 32 bits, others
// to 64. We always ty to give them natural alignment.
if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
Ret += "-v64:32:64-v128:32:128";
else if (ABI != ARMBaseTargetMachine::ARM_ABI_AAPCS16)
Ret += "-v128:64:128";
// Try to align aggregates to 32 bits (the default is 64 bits, which has no
// particular hardware support on 32-bit ARM).
Ret += "-a:0:32";
// Integer registers are 32 bits.
Ret += "-n32";
// The stack is 128 bit aligned on NaCl, 64 bit aligned on AAPCS and 32 bit
// aligned everywhere else.
if (TT.isOSNaCl() || ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS16)
Ret += "-S128";
else if (ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS)
Ret += "-S64";
else
Ret += "-S32";
return Ret;
}
static Reloc::Model getEffectiveRelocModel(const Triple &TT,
Optional<Reloc::Model> RM) {
if (!RM.hasValue())
// Default relocation model on Darwin is PIC.
return TT.isOSBinFormatMachO() ? Reloc::PIC_ : Reloc::Static;
if (*RM == Reloc::ROPI || *RM == Reloc::RWPI || *RM == Reloc::ROPI_RWPI)
assert(TT.isOSBinFormatELF() &&
"ROPI/RWPI currently only supported for ELF");
// DynamicNoPIC is only used on darwin.
if (*RM == Reloc::DynamicNoPIC && !TT.isOSDarwin())
return Reloc::Static;
return *RM;
}
/// Create an ARM architecture model.
///
ARMBaseTargetMachine::ARMBaseTargetMachine(const Target &T, const Triple &TT,
StringRef CPU, StringRef FS,
const TargetOptions &Options,
Optional<Reloc::Model> RM,
Optional<CodeModel::Model> CM,
CodeGenOpt::Level OL, bool isLittle)
: LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options, isLittle), TT,
CPU, FS, Options, getEffectiveRelocModel(TT, RM),
getEffectiveCodeModel(CM, CodeModel::Small), OL),
TargetABI(computeTargetABI(TT, CPU, Options)),
TLOF(createTLOF(getTargetTriple())), isLittle(isLittle) {
// Default to triple-appropriate float ABI
if (Options.FloatABIType == FloatABI::Default) {
if (isTargetHardFloat())
this->Options.FloatABIType = FloatABI::Hard;
else
this->Options.FloatABIType = FloatABI::Soft;
}
// Default to triple-appropriate EABI
if (Options.EABIVersion == EABI::Default ||
Options.EABIVersion == EABI::Unknown) {
// musl is compatible with glibc with regard to EABI version
if ((TargetTriple.getEnvironment() == Triple::GNUEABI ||
TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
TargetTriple.getEnvironment() == Triple::MuslEABI ||
TargetTriple.getEnvironment() == Triple::MuslEABIHF) &&
!(TargetTriple.isOSWindows() || TargetTriple.isOSDarwin()))
this->Options.EABIVersion = EABI::GNU;
else
this->Options.EABIVersion = EABI::EABI5;
}
if (TT.isOSBinFormatMachO()) {
this->Options.TrapUnreachable = true;
this->Options.NoTrapAfterNoreturn = true;
}
initAsmInfo();
}
ARMBaseTargetMachine::~ARMBaseTargetMachine() = default;
const ARMSubtarget *
ARMBaseTargetMachine::getSubtargetImpl(const Function &F) const {
Attribute CPUAttr = F.getFnAttribute("target-cpu");
Attribute FSAttr = F.getFnAttribute("target-features");
std::string CPU = !CPUAttr.hasAttribute(Attribute::None)
? CPUAttr.getValueAsString().str()
: TargetCPU;
std::string FS = !FSAttr.hasAttribute(Attribute::None)
? FSAttr.getValueAsString().str()
: TargetFS;
// FIXME: This is related to the code below to reset the target options,
// we need to know whether or not the soft float flag is set on the
// function before we can generate a subtarget. We also need to use
// it as a key for the subtarget since that can be the only difference
// between two functions.
bool SoftFloat =
F.getFnAttribute("use-soft-float").getValueAsString() == "true";
// If the soft float attribute is set on the function turn on the soft float
// subtarget feature.
if (SoftFloat)
FS += FS.empty() ? "+soft-float" : ",+soft-float";
// Use the optminsize to identify the subtarget, but don't use it in the
// feature string.
std::string Key = CPU + FS;
if (F.hasMinSize())
Key += "+minsize";
auto &I = SubtargetMap[Key];
if (!I) {
// This needs to be done before we create a new subtarget since any
// creation will depend on the TM and the code generation flags on the
// function that reside in TargetOptions.
resetTargetOptions(F);
I = std::make_unique<ARMSubtarget>(TargetTriple, CPU, FS, *this, isLittle,
F.hasMinSize());
if (!I->isThumb() && !I->hasARMOps())
F.getContext().emitError("Function '" + F.getName() + "' uses ARM "
"instructions, but the target does not support ARM mode execution.");
}
return I.get();
}
TargetTransformInfo
ARMBaseTargetMachine::getTargetTransformInfo(const Function &F) {
return TargetTransformInfo(ARMTTIImpl(this, F));
}
ARMLETargetMachine::ARMLETargetMachine(const Target &T, const Triple &TT,
StringRef CPU, StringRef FS,
const TargetOptions &Options,
Optional<Reloc::Model> RM,
Optional<CodeModel::Model> CM,
CodeGenOpt::Level OL, bool JIT)
: ARMBaseTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, true) {}
ARMBETargetMachine::ARMBETargetMachine(const Target &T, const Triple &TT,
StringRef CPU, StringRef FS,
const TargetOptions &Options,
Optional<Reloc::Model> RM,
Optional<CodeModel::Model> CM,
CodeGenOpt::Level OL, bool JIT)
: ARMBaseTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, false) {}
namespace {
/// ARM Code Generator Pass Configuration Options.
class ARMPassConfig : public TargetPassConfig {
public:
ARMPassConfig(ARMBaseTargetMachine &TM, PassManagerBase &PM)
: TargetPassConfig(TM, PM) {}
ARMBaseTargetMachine &getARMTargetMachine() const {
return getTM<ARMBaseTargetMachine>();
}
ScheduleDAGInstrs *
createMachineScheduler(MachineSchedContext *C) const override {
ScheduleDAGMILive *DAG = createGenericSchedLive(C);
// add DAG Mutations here.
const ARMSubtarget &ST = C->MF->getSubtarget<ARMSubtarget>();
if (ST.hasFusion())
DAG->addMutation(createARMMacroFusionDAGMutation());
return DAG;
}
ScheduleDAGInstrs *
createPostMachineScheduler(MachineSchedContext *C) const override {
ScheduleDAGMI *DAG = createGenericSchedPostRA(C);
// add DAG Mutations here.
const ARMSubtarget &ST = C->MF->getSubtarget<ARMSubtarget>();
if (ST.hasFusion())
DAG->addMutation(createARMMacroFusionDAGMutation());
return DAG;
}
void addIRPasses() override;
void addCodeGenPrepare() override;
bool addPreISel() override;
bool addInstSelector() override;
bool addIRTranslator() override;
bool addLegalizeMachineIR() override;
bool addRegBankSelect() override;
bool addGlobalInstructionSelect() override;
void addPreRegAlloc() override;
void addPreSched2() override;
void addPreEmitPass() override;
std::unique_ptr<CSEConfigBase> getCSEConfig() const override;
};
class ARMExecutionDomainFix : public ExecutionDomainFix {
public:
static char ID;
ARMExecutionDomainFix() : ExecutionDomainFix(ID, ARM::DPRRegClass) {}
StringRef getPassName() const override {
return "ARM Execution Domain Fix";
}
};
char ARMExecutionDomainFix::ID;
} // end anonymous namespace
INITIALIZE_PASS_BEGIN(ARMExecutionDomainFix, "arm-execution-domain-fix",
"ARM Execution Domain Fix", false, false)
INITIALIZE_PASS_DEPENDENCY(ReachingDefAnalysis)
INITIALIZE_PASS_END(ARMExecutionDomainFix, "arm-execution-domain-fix",
"ARM Execution Domain Fix", false, false)
TargetPassConfig *ARMBaseTargetMachine::createPassConfig(PassManagerBase &PM) {
return new ARMPassConfig(*this, PM);
}
std::unique_ptr<CSEConfigBase> ARMPassConfig::getCSEConfig() const {
return getStandardCSEConfigForOpt(TM->getOptLevel());
}
void ARMPassConfig::addIRPasses() {
if (TM->Options.ThreadModel == ThreadModel::Single)
addPass(createLowerAtomicPass());
else
addPass(createAtomicExpandPass());
// Cmpxchg instructions are often used with a subsequent comparison to
// determine whether it succeeded. We can exploit existing control-flow in
// ldrex/strex loops to simplify this, but it needs tidying up.
if (TM->getOptLevel() != CodeGenOpt::None && EnableAtomicTidy)
addPass(createCFGSimplificationPass(
1, false, false, true, true, [this](const Function &F) {
const auto &ST = this->TM->getSubtarget<ARMSubtarget>(F);
return ST.hasAnyDataBarrier() && !ST.isThumb1Only();
}));
TargetPassConfig::addIRPasses();
// Run the parallel DSP pass.
if (getOptLevel() == CodeGenOpt::Aggressive)
addPass(createARMParallelDSPPass());
// Match interleaved memory accesses to ldN/stN intrinsics.
if (TM->getOptLevel() != CodeGenOpt::None)
addPass(createInterleavedAccessPass());
// Add Control Flow Guard checks.
if (TM->getTargetTriple().isOSWindows())
addPass(createCFGuardCheckPass());
}
void ARMPassConfig::addCodeGenPrepare() {
if (getOptLevel() != CodeGenOpt::None)
addPass(createARMCodeGenPreparePass());
TargetPassConfig::addCodeGenPrepare();
}
bool ARMPassConfig::addPreISel() {
if ((TM->getOptLevel() != CodeGenOpt::None &&
EnableGlobalMerge == cl::BOU_UNSET) ||
EnableGlobalMerge == cl::BOU_TRUE) {
// FIXME: This is using the thumb1 only constant value for
// maximal global offset for merging globals. We may want
// to look into using the old value for non-thumb1 code of
// 4095 based on the TargetMachine, but this starts to become
// tricky when doing code gen per function.
bool OnlyOptimizeForSize = (TM->getOptLevel() < CodeGenOpt::Aggressive) &&
(EnableGlobalMerge == cl::BOU_UNSET);
// Merging of extern globals is enabled by default on non-Mach-O as we
// expect it to be generally either beneficial or harmless. On Mach-O it
// is disabled as we emit the .subsections_via_symbols directive which
// means that merging extern globals is not safe.
bool MergeExternalByDefault = !TM->getTargetTriple().isOSBinFormatMachO();
addPass(createGlobalMergePass(TM, 127, OnlyOptimizeForSize,
MergeExternalByDefault));
}
if (TM->getOptLevel() != CodeGenOpt::None) {
addPass(createHardwareLoopsPass());
addPass(createMVETailPredicationPass());
}
return false;
}
bool ARMPassConfig::addInstSelector() {
addPass(createARMISelDag(getARMTargetMachine(), getOptLevel()));
return false;
}
bool ARMPassConfig::addIRTranslator() {
addPass(new IRTranslator());
return false;
}
bool ARMPassConfig::addLegalizeMachineIR() {
addPass(new Legalizer());
return false;
}
bool ARMPassConfig::addRegBankSelect() {
addPass(new RegBankSelect());
return false;
}
bool ARMPassConfig::addGlobalInstructionSelect() {
addPass(new InstructionSelect());
return false;
}
void ARMPassConfig::addPreRegAlloc() {
if (getOptLevel() != CodeGenOpt::None) {
addPass(createMLxExpansionPass());
if (EnableARMLoadStoreOpt)
addPass(createARMLoadStoreOptimizationPass(/* pre-register alloc */ true));
if (!DisableA15SDOptimization)
addPass(createA15SDOptimizerPass());
}
}
void ARMPassConfig::addPreSched2() {
if (getOptLevel() != CodeGenOpt::None) {
if (EnableARMLoadStoreOpt)
addPass(createARMLoadStoreOptimizationPass());
addPass(new ARMExecutionDomainFix());
addPass(createBreakFalseDeps());
}
// Expand some pseudo instructions into multiple instructions to allow
// proper scheduling.
addPass(createARMExpandPseudoPass());
if (getOptLevel() != CodeGenOpt::None) {
// in v8, IfConversion depends on Thumb instruction widths
addPass(createThumb2SizeReductionPass([this](const Function &F) {
return this->TM->getSubtarget<ARMSubtarget>(F).restrictIT();
}));
addPass(createIfConverter([](const MachineFunction &MF) {
return !MF.getSubtarget<ARMSubtarget>().isThumb1Only();
}));
}
addPass(createMVEVPTBlockPass());
addPass(createThumb2ITBlockPass());
// Add both scheduling passes to give the subtarget an opportunity to pick
// between them.
if (getOptLevel() != CodeGenOpt::None) {
addPass(&PostMachineSchedulerID);
addPass(&PostRASchedulerID);
}
}
void ARMPassConfig::addPreEmitPass() {
addPass(createThumb2SizeReductionPass());
// Constant island pass work on unbundled instructions.
addPass(createUnpackMachineBundles([](const MachineFunction &MF) {
return MF.getSubtarget<ARMSubtarget>().isThumb2();
}));
// Don't optimize barriers at -O0.
if (getOptLevel() != CodeGenOpt::None)
addPass(createARMOptimizeBarriersPass());
addPass(createARMConstantIslandPass());
addPass(createARMLowOverheadLoopsPass());
// Identify valid longjmp targets for Windows Control Flow Guard.
if (TM->getTargetTriple().isOSWindows())
addPass(createCFGuardLongjmpPass());
}
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