llvm/lib/Target/SPIRV/SPIRVTargetMachine.cpp

//===- SPIRVTargetMachine.cpp - Define TargetMachine for SPIR-V -*- 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
//
//===----------------------------------------------------------------------===//
//
// Implements the info about SPIR-V target spec.
//
//===----------------------------------------------------------------------===//

#include "SPIRVTargetMachine.h"
#include "Analysis/SPIRVConvergenceRegionAnalysis.h"
#include "SPIRV.h"
#include "SPIRVGlobalRegistry.h"
#include "SPIRVLegalizerInfo.h"
#include "SPIRVTargetObjectFile.h"
#include "SPIRVTargetTransformInfo.h"
#include "TargetInfo/SPIRVTargetInfo.h"
#include "llvm/CodeGen/GlobalISel/IRTranslator.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
#include "llvm/CodeGen/GlobalISel/Legalizer.h"
#include "llvm/CodeGen/GlobalISel/RegBankSelect.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/InitializePasses.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Pass.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Transforms/IPO/ExpandVariadics.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils.h"
#include <optional>

using namespace llvm;

extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void LLVMInitializeSPIRVTarget() {
  // Register the target.
  RegisterTargetMachine<SPIRVTargetMachine> X(getTheSPIRV32Target());
  RegisterTargetMachine<SPIRVTargetMachine> Y(getTheSPIRV64Target());
  RegisterTargetMachine<SPIRVTargetMachine> Z(getTheSPIRVLogicalTarget());

  PassRegistry &PR = *PassRegistry::getPassRegistry();
  initializeGlobalISel(PR);
  initializeSPIRVModuleAnalysisWrapperPassPass(PR);
  initializeSPIRVAsmPrinterPass(PR);
  initializeSPIRVConvergenceRegionAnalysisWrapperPassPass(PR);
  initializeSPIRVStructurizerPass(PR);
  initializeSPIRVCBufferAccessLegacyPass(PR);
  initializeSPIRVPushConstantAccessLegacyPass(PR);
  initializeSPIRVPreLegalizerCombinerLegacyPass(PR);
  initializeSPIRVLegalizePointerCastLegacyPass(PR);
  initializeSPIRVLegalizeZeroSizeArraysLegacyPass(PR);
  initializeSPIRVRegularizerLegacyPass(PR);
  initializeSPIRVPreLegalizerLegacyPass(PR);
  initializeSPIRVPostLegalizerLegacyPass(PR);
  initializeSPIRVPrepareModuleAnalysisLegacyPass(PR);
  initializeSPIRVMergeRegionExitTargetsLegacyPass(PR);
  initializeSPIRVEmitIntrinsicsLegacyPass(PR);
  initializeSPIRVPrepareFunctionsLegacyPass(PR);
  initializeSPIRVPrepareGlobalsLegacyPass(PR);
  initializeSPIRVLegalizeResourceBindingLegacyPass(PR);
  initializeSPIRVCtorDtorLoweringLegacyPass(PR);
  initializeSPIRVFinalizeShaderLinkageLegacyPass(PR);
}

static Reloc::Model getEffectiveRelocModel(std::optional<Reloc::Model> RM) {
  if (!RM)
    return Reloc::PIC_;
  return *RM;
}

// Pin SPIRVTargetObjectFile's vtables to this file.
SPIRVTargetObjectFile::~SPIRVTargetObjectFile() = default;

SPIRVTargetMachine::SPIRVTargetMachine(const Target &T, const Triple &TT,
                                       StringRef CPU, StringRef FS,
                                       const TargetOptions &Options,
                                       std::optional<Reloc::Model> RM,
                                       std::optional<CodeModel::Model> CM,
                                       CodeGenOptLevel OL, bool JIT)
    : CodeGenTargetMachineImpl(T, TT, CPU, FS, Options,
                               getEffectiveRelocModel(RM),
                               getEffectiveCodeModel(CM, CodeModel::Small), OL),
      TLOF(std::make_unique<SPIRVTargetObjectFile>()),
      Subtarget(TT, CPU.str(), FS.str(), *this) {
  initAsmInfo();
  setGlobalISel(true);
  setFastISel(false);
  setO0WantsFastISel(false);
  setRequiresStructuredCFG(false);
}

namespace {
// SPIR-V Code Generator Pass Configuration Options.
class SPIRVPassConfig : public TargetPassConfig {
public:
  SPIRVPassConfig(SPIRVTargetMachine &TM, PassManagerBase &PM)
      : TargetPassConfig(TM, PM), TM(TM) {}

  SPIRVTargetMachine &getSPIRVTargetMachine() const {
    return getTM<SPIRVTargetMachine>();
  }
  void addMachineSSAOptimization() override;
  void addIRPasses() override;
  void addISelPrepare() override;

  bool addIRTranslator() override;
  void addPreLegalizeMachineIR() override;
  bool addLegalizeMachineIR() override;
  bool addRegBankSelect() override;
  bool addGlobalInstructionSelect() override;

  FunctionPass *createTargetRegisterAllocator(bool) override;
  void addFastRegAlloc() override {}
  void addOptimizedRegAlloc() override {}

  void addPostRegAlloc() override;
  void addPreEmitPass2() override;

private:
  const SPIRVTargetMachine &TM;
};
} // namespace

// We do not use physical registers, and maintain virtual registers throughout
// the entire pipeline, so return nullptr to disable register allocation.
FunctionPass *SPIRVPassConfig::createTargetRegisterAllocator(bool) {
  return nullptr;
}

// A place to disable passes that may break CFG.
void SPIRVPassConfig::addMachineSSAOptimization() {
  TargetPassConfig::addMachineSSAOptimization();
}

// Disable passes that break from assuming no virtual registers exist.
void SPIRVPassConfig::addPostRegAlloc() {
  // Do not work with vregs instead of physical regs.
  disablePass(&MachineCopyPropagationID);
  disablePass(&PostRAMachineSinkingID);
  disablePass(&PostRASchedulerID);
  disablePass(&FuncletLayoutID);
  disablePass(&StackMapLivenessID);
  disablePass(&PatchableFunctionID);
  disablePass(&ShrinkWrapID);
  disablePass(&LiveDebugValuesID);
  disablePass(&MachineLateInstrsCleanupID);
  disablePass(&RemoveLoadsIntoFakeUsesID);

  // Do not work with OpPhi.
  disablePass(&BranchFolderPassID);
  disablePass(&MachineBlockPlacementID);

  TargetPassConfig::addPostRegAlloc();
}

void SPIRVPassConfig::addPreEmitPass2() {
  addPass(createSPIRVPrepareModuleAnalysisLegacyPass());
}

TargetTransformInfo
SPIRVTargetMachine::getTargetTransformInfo(const Function &F) const {
  return TargetTransformInfo(std::make_unique<SPIRVTTIImpl>(this, F));
}

TargetPassConfig *SPIRVTargetMachine::createPassConfig(PassManagerBase &PM) {
  return new SPIRVPassConfig(*this, PM);
}

void SPIRVPassConfig::addIRPasses() {
  addPass(createAtomicExpandLegacyPass());

  TargetPassConfig::addIRPasses();

  if (TM.getSubtargetImpl()->isShader()) {
    if (getOptLevel() != CodeGenOptLevel::None)
      addPass(createSPIRVFinalizeShaderLinkagePass(TM));
  } else {
    // Variadic function calls aren't supported in shader code.
    // This needs to come before SPIRVPrepareFunctions because this
    // may introduce intrinsic calls.
    addPass(createExpandVariadicsPass(ExpandVariadicsMode::Lowering));
  }

  addPass(createSPIRVRegularizerPass());
  addPass(createSPIRVCtorDtorLoweringLegacyPass());
  addPass(createSPIRVPrepareFunctionsPass(TM));
  addPass(createSPIRVPrepareGlobalsPass());
}

void SPIRVPassConfig::addISelPrepare() {
  if (TM.getSubtargetImpl()->isShader()) {
    // Vulkan does not allow address space casts. This pass is run to remove
    // address space casts that can be removed.
    // If an address space cast is not removed while targeting Vulkan, lowering
    // will fail during MIR lowering.
    addPass(createInferAddressSpacesPass());

    // 1.  Simplify loop for subsequent transformations. After this steps, loops
    // have the following properties:
    //  - loops have a single entry edge (pre-header to loop header).
    //  - all loop exits are dominated by the loop pre-header.
    //  - loops have a single back-edge.
    addPass(createLoopSimplifyPass());

    // 2. Removes registers whose lifetime spans across basic blocks. Also
    // removes phi nodes. This will greatly simplify the next steps.
    addPass(createRegToMemWrapperPass());

    // 3. Merge the convergence region exit nodes into one. After this step,
    // regions are single-entry, single-exit. This will help determine the
    // correct merge block.
    addPass(createSPIRVMergeRegionExitTargetsPass());

    // 4. Structurize.
    addPass(createSPIRVStructurizerPass());

    // 5. Reduce the amount of variables required by pushing some operations
    // back to virtual registers.
    addPass(createPromoteMemoryToRegisterPass());
  } else {
    // Canonicalize loops so they have a single latch and preheader.
    // This enables OpLoopMerge emission for non-shader targets.
    addPass(createLoopSimplifyPass());
  }
  SPIRVTargetMachine &TM = getTM<SPIRVTargetMachine>();
  addPass(createStripConvergenceIntrinsicsPass());
  addPass(createSPIRVLegalizeResourceBindingPass());
  addPass(createSPIRVLegalizeZeroSizeArraysPass(TM));
  addPass(createSPIRVCBufferAccessLegacyPass());
  addPass(createSPIRVPushConstantAccessLegacyPass(&TM));
  addPass(createSPIRVEmitIntrinsicsPass(TM));
  if (TM.getSubtargetImpl()->isLogicalSPIRV())
    addPass(createSPIRVLegalizePointerCastPass(&TM));
  TargetPassConfig::addISelPrepare();
}

bool SPIRVPassConfig::addIRTranslator() {
  addPass(new IRTranslatorLegacy(getOptLevel()));
  return false;
}

void SPIRVPassConfig::addPreLegalizeMachineIR() {
  addPass(createSPIRVPreLegalizerCombinerLegacyPass());
  addPass(createSPIRVPreLegalizerLegacyPass());
}

// Use the default legalizer.
bool SPIRVPassConfig::addLegalizeMachineIR() {
  addPass(new LegalizerLegacy());
  addPass(createSPIRVPostLegalizerLegacyPass());
  return false;
}

// Do not add the RegBankSelect pass, as we only ever need virtual registers.
bool SPIRVPassConfig::addRegBankSelect() {
  disablePass(&RegBankSelectLegacy::ID);
  return false;
}

// Deprecated flag kept for backward compatibility. NSDI emission is now handled
// by SPIRVNonSemanticDebugHandler, registered in SPIRVAsmPrinter::
// doInitialization() when the module contains debug info (llvm.dbg.cu).
// TODO: Remove this option after a deprecation period. Callers that used
// -spv-emit-nonsemantic-debug-info should switch to -g.
static cl::opt<bool> SPVEnableNonSemanticDI(
    "spv-emit-nonsemantic-debug-info",
    cl::desc("Deprecated. Use -g to emit SPIR-V NonSemantic.Shader.DebugInfo "
             "instructions"),
    cl::init(false));

// Add the custom SPIRVInstructionSelect from above.
bool SPIRVPassConfig::addGlobalInstructionSelect() {
  addPass(new InstructionSelectLegacy(getOptLevel(),
                                      /*RequireRegBankSelection=*/false));
  return false;
}