lib/DXIL/DxilUtilDbgInfoAndMisc.cpp

///////////////////////////////////////////////////////////////////////////////
//                                                                           //
// DxilUtilDbgInfoAndMisc.cpp                                                //
// Copyright (C) Microsoft Corporation. All rights reserved.                 //
// This file is distributed under the University of Illinois Open Source     //
// License. See LICENSE.TXT for details.                                     //
//                                                                           //
// Dxil helper functions.                                                    //
//                                                                           //
///////////////////////////////////////////////////////////////////////////////

#include "dxc/DXIL/DxilModule.h"
#include "dxc/DXIL/DxilOperations.h"
#include "dxc/DXIL/DxilTypeSystem.h"
#include "dxc/DXIL/DxilUtil.h"
#include "dxc/HLSL/DxilConvergentName.h"
#include "dxc/Support/Global.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;
using namespace hlsl;

namespace {

// Attempt to merge the two GEPs into a single GEP.
//
// If `AsCast` is non-null the merged GEP will be wrapped
// in an addrspacecast before replacing users. This allows
// merging GEPs of the form
//
//      gep(addrspacecast(gep(p0, gep_args0) to p1*), gep_args1)
// into
//      addrspacecast(gep(p0, gep_args0+gep_args1) to p1*)
//
Value *MergeGEP(GEPOperator *SrcGEP, GEPOperator *GEP,
                AddrSpaceCastOperator *AsCast) {
  IRBuilder<> Builder(GEP->getContext());
  StringRef Name = "";
  if (Instruction *I = dyn_cast<Instruction>(GEP)) {
    Builder.SetInsertPoint(I);
    Name = GEP->getName();
  }
  SmallVector<Value *, 8> Indices;

  // Find out whether the last index in the source GEP is a sequential idx.
  bool EndsWithSequential = false;
  for (gep_type_iterator I = gep_type_begin(*SrcGEP), E = gep_type_end(*SrcGEP);
       I != E; ++I)
    EndsWithSequential = !(*I)->isStructTy();
  if (EndsWithSequential) {
    Value *Sum;
    Value *SO1 = SrcGEP->getOperand(SrcGEP->getNumOperands() - 1);
    Value *GO1 = GEP->getOperand(1);
    if (SO1 == Constant::getNullValue(SO1->getType())) {
      Sum = GO1;
    } else if (GO1 == Constant::getNullValue(GO1->getType())) {
      Sum = SO1;
    } else {
      // If they aren't the same type, then the input hasn't been processed
      // by the loop above yet (which canonicalizes sequential index types to
      // intptr_t).  Just avoid transforming this until the input has been
      // normalized.
      if (SO1->getType() != GO1->getType())
        return nullptr;
      // Only do the combine when GO1 and SO1 are both constants. Only in
      // this case, we are sure the cost after the merge is never more than
      // that before the merge.
      if (!isa<Constant>(GO1) || !isa<Constant>(SO1))
        return nullptr;
      Sum = Builder.CreateAdd(SO1, GO1);
    }

    // Update the GEP in place if possible.
    if (SrcGEP->getNumOperands() == 2 && !AsCast) {
      GEP->setOperand(0, SrcGEP->getOperand(0));
      GEP->setOperand(1, Sum);
      return GEP;
    }
    Indices.append(SrcGEP->op_begin() + 1, SrcGEP->op_end() - 1);
    Indices.push_back(Sum);
    Indices.append(GEP->op_begin() + 2, GEP->op_end());
  } else if (isa<Constant>(*GEP->idx_begin()) &&
             cast<Constant>(*GEP->idx_begin())->isNullValue() &&
             SrcGEP->getNumOperands() != 1) {
    // Otherwise we can do the fold if the first index of the GEP is a zero
    Indices.append(SrcGEP->op_begin() + 1, SrcGEP->op_end());
    Indices.append(GEP->idx_begin() + 1, GEP->idx_end());
  }

  DXASSERT(!Indices.empty(), "must merge");
  Value *newGEP =
      Builder.CreateInBoundsGEP(nullptr, SrcGEP->getOperand(0), Indices, Name);

  // Wrap the new gep in an addrspacecast if needed.
  if (AsCast)
    newGEP = Builder.CreateAddrSpaceCast(
        newGEP, PointerType::get(GEP->getType()->getPointerElementType(),
                                 AsCast->getDestAddressSpace()));
  GEP->replaceAllUsesWith(newGEP);
  if (Instruction *I = dyn_cast<Instruction>(GEP))
    I->eraseFromParent();
  return newGEP;
}

// Examine the gep and try to merge it when the input pointer is
// itself a gep. We handle two forms here:
//
//      gep(gep(p))
//      gep(addrspacecast(gep(p)))
//
// If the gep was merged successfully then return the updated value, otherwise
// return nullptr.
//
// When the gep is sucessfully merged we will delete the gep and also try to
// delete the nested gep and addrspacecast.
static Value *TryMegeWithNestedGEP(GEPOperator *GEP) {
  // Sentinal value to return when we fail to merge.
  Value *FailedToMerge = nullptr;

  Value *Ptr = GEP->getPointerOperand();
  GEPOperator *prevGEP = dyn_cast<GEPOperator>(Ptr);
  AddrSpaceCastOperator *AsCast = nullptr;

  // If there is no directly nested gep try looking through an addrspacecast to
  // find one.
  if (!prevGEP) {
    AsCast = dyn_cast<AddrSpaceCastOperator>(Ptr);
    if (AsCast)
      prevGEP = dyn_cast<GEPOperator>(AsCast->getPointerOperand());
  }

  // Not a nested gep expression.
  if (!prevGEP)
    return FailedToMerge;

  // Try merging the two geps.
  Value *newGEP = MergeGEP(prevGEP, GEP, AsCast);
  if (!newGEP)
    return FailedToMerge;

  // Delete the nested gep and addrspacecast if no more users.
  if (AsCast && AsCast->user_empty() && isa<AddrSpaceCastInst>(AsCast))
    cast<AddrSpaceCastInst>(AsCast)->eraseFromParent();

  if (prevGEP->user_empty() && isa<GetElementPtrInst>(prevGEP))
    cast<GetElementPtrInst>(prevGEP)->eraseFromParent();

  return newGEP;
}

} // namespace

namespace hlsl {

namespace dxilutil {

bool MergeGepUse(Value *V) {
  bool changed = false;
  SmallVector<Value *, 16> worklist;
  auto addUsersToWorklist = [&worklist](Value *V) {
    if (!V->user_empty()) {
      // Add users in reverse to the worklist, so they are processed in order
      // This makes it equivalent to recursive traversal
      size_t start = worklist.size();
      worklist.append(V->user_begin(), V->user_end());
      size_t end = worklist.size();
      std::reverse(worklist.data() + start, worklist.data() + end);
    }
  };
  addUsersToWorklist(V);
  while (worklist.size()) {
    V = worklist.pop_back_val();
    if (isa<BitCastOperator>(V)) {
      if (Value *NewV = dxilutil::TryReplaceBaseCastWithGep(V)) {
        changed = true;
        worklist.push_back(NewV);
      } else {
        // merge any GEP users of the untranslated bitcast
        addUsersToWorklist(V);
      }
    } else if (isa<AddrSpaceCastOperator>(V)) {
      addUsersToWorklist(V);
    } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
      if (Value *newGEP = TryMegeWithNestedGEP(GEP)) {
        changed = true;
        worklist.push_back(newGEP);
      } else {
        addUsersToWorklist(GEP);
      }
    }
  }

  return changed;
}

std::unique_ptr<llvm::Module> LoadModuleFromBitcode(llvm::MemoryBuffer *MB,
                                                    llvm::LLVMContext &Ctx,
                                                    std::string &DiagStr) {
  // Note: the DiagStr is not used.
  auto pModule = llvm::parseBitcodeFile(MB->getMemBufferRef(), Ctx);
  if (!pModule) {
    return nullptr;
  }
  return std::unique_ptr<llvm::Module>(pModule.get().release());
}

std::unique_ptr<llvm::Module>
LoadModuleFromBitcodeLazy(std::unique_ptr<llvm::MemoryBuffer> &&MB,
                          llvm::LLVMContext &Ctx, std::string &DiagStr) {
  // Note: the DiagStr is not used.
  auto pModule = llvm::getLazyBitcodeModule(std::move(MB), Ctx, nullptr, true);
  if (!pModule) {
    return nullptr;
  }
  return std::unique_ptr<llvm::Module>(pModule.get().release());
}

std::unique_ptr<llvm::Module> LoadModuleFromBitcode(llvm::StringRef BC,
                                                    llvm::LLVMContext &Ctx,
                                                    std::string &DiagStr) {
  std::unique_ptr<llvm::MemoryBuffer> pBitcodeBuf(
      llvm::MemoryBuffer::getMemBuffer(BC, "", false));
  return LoadModuleFromBitcode(pBitcodeBuf.get(), Ctx, DiagStr);
}

DIGlobalVariable *FindGlobalVariableDebugInfo(GlobalVariable *GV,
                                              DebugInfoFinder &DbgInfoFinder) {
  struct GlobalFinder {
    GlobalVariable *GV;
    bool operator()(llvm::DIGlobalVariable *const arg) const {
      return arg->getVariable() == GV;
    }
  };
  GlobalFinder F = {GV};
  DebugInfoFinder::global_variable_iterator Found =
      std::find_if(DbgInfoFinder.global_variables().begin(),
                   DbgInfoFinder.global_variables().end(), F);
  if (Found != DbgInfoFinder.global_variables().end()) {
    return *Found;
  }
  return nullptr;
}

static void EmitWarningOrErrorOnInstruction(Instruction *I, Twine Msg,
                                            DiagnosticSeverity severity);

// If we don't have debug location and this is select/phi,
// try recursing users to find instruction with debug info.
// Only recurse phi/select and limit depth to prevent doing
// too much work if no debug location found.
static bool
EmitWarningOrErrorOnInstructionFollowPhiSelect(Instruction *I, Twine Msg,
                                               DiagnosticSeverity severity,
                                               unsigned depth = 0) {
  if (depth > 4)
    return false;
  if (I->getDebugLoc().get()) {
    EmitWarningOrErrorOnInstruction(I, Msg, severity);
    return true;
  }
  if (isa<PHINode>(I) || isa<SelectInst>(I)) {
    for (auto U : I->users())
      if (Instruction *UI = dyn_cast<Instruction>(U))
        if (EmitWarningOrErrorOnInstructionFollowPhiSelect(UI, Msg, severity,
                                                           depth + 1))
          return true;
  }
  return false;
}

static void EmitWarningOrErrorOnInstruction(Instruction *I, Twine Msg,
                                            DiagnosticSeverity severity) {
  const DebugLoc &DL = I->getDebugLoc();
  if (!DL.get() && (isa<PHINode>(I) || isa<SelectInst>(I))) {
    if (EmitWarningOrErrorOnInstructionFollowPhiSelect(I, Msg, severity))
      return;
  }

  I->getContext().diagnose(
      DiagnosticInfoDxil(I->getParent()->getParent(), DL.get(), Msg, severity));
}

void EmitErrorOnInstruction(Instruction *I, Twine Msg) {
  EmitWarningOrErrorOnInstruction(I, Msg, DiagnosticSeverity::DS_Error);
}

void EmitWarningOnInstruction(Instruction *I, Twine Msg) {
  EmitWarningOrErrorOnInstruction(I, Msg, DiagnosticSeverity::DS_Warning);
}

static void EmitWarningOrErrorOnFunction(llvm::LLVMContext &Ctx, Function *F,
                                         Twine Msg,
                                         DiagnosticSeverity severity) {
  DILocation *DLoc = nullptr;

  if (DISubprogram *DISP = getDISubprogram(F)) {
    DLoc = DILocation::get(F->getContext(), DISP->getLine(), 0, DISP,
                           nullptr /*InlinedAt*/);
  }
  Ctx.diagnose(DiagnosticInfoDxil(F, DLoc, Msg, severity));
}

void EmitErrorOnFunction(llvm::LLVMContext &Ctx, Function *F, Twine Msg) {
  EmitWarningOrErrorOnFunction(Ctx, F, Msg, DiagnosticSeverity::DS_Error);
}

void EmitWarningOnFunction(llvm::LLVMContext &Ctx, Function *F, Twine Msg) {
  EmitWarningOrErrorOnFunction(Ctx, F, Msg, DiagnosticSeverity::DS_Warning);
}

static void EmitWarningOrErrorOnGlobalVariable(llvm::LLVMContext &Ctx,
                                               GlobalVariable *GV, Twine Msg,
                                               DiagnosticSeverity severity) {
  DIGlobalVariable *DIV = nullptr;

  if (GV) {
    Module &M = *GV->getParent();
    if (hasDebugInfo(M)) {
      DebugInfoFinder FinderObj;
      DebugInfoFinder &Finder = FinderObj;
      // Debug modules have no dxil modules. Use it if you got it.
      if (M.HasDxilModule())
        Finder = M.GetDxilModule().GetOrCreateDebugInfoFinder();
      else
        Finder.processModule(M);
      DIV = FindGlobalVariableDebugInfo(GV, Finder);
    }
  }

  Ctx.diagnose(DiagnosticInfoDxil(nullptr /*Function*/, DIV, Msg, severity));
}

void EmitErrorOnGlobalVariable(llvm::LLVMContext &Ctx, GlobalVariable *GV,
                               Twine Msg) {
  EmitWarningOrErrorOnGlobalVariable(Ctx, GV, Msg,
                                     DiagnosticSeverity::DS_Error);
}

void EmitWarningOnGlobalVariable(llvm::LLVMContext &Ctx, GlobalVariable *GV,
                                 Twine Msg) {
  EmitWarningOrErrorOnGlobalVariable(Ctx, GV, Msg,
                                     DiagnosticSeverity::DS_Warning);
}

const char *kResourceMapErrorMsg =
    "local resource not guaranteed to map to unique global resource.";
void EmitResMappingError(Instruction *Res) {
  EmitErrorOnInstruction(Res, kResourceMapErrorMsg);
}

// Mostly just a locationless diagnostic output
static void EmitWarningOrErrorOnContext(LLVMContext &Ctx, Twine Msg,
                                        DiagnosticSeverity severity) {
  Ctx.diagnose(DiagnosticInfoDxil(nullptr /*Func*/, Msg, severity));
}

void EmitErrorOnContext(LLVMContext &Ctx, Twine Msg) {
  EmitWarningOrErrorOnContext(Ctx, Msg, DiagnosticSeverity::DS_Error);
}

void EmitWarningOnContext(LLVMContext &Ctx, Twine Msg) {
  EmitWarningOrErrorOnContext(Ctx, Msg, DiagnosticSeverity::DS_Warning);
}

void EmitNoteOnContext(LLVMContext &Ctx, Twine Msg) {
  EmitWarningOrErrorOnContext(Ctx, Msg, DiagnosticSeverity::DS_Note);
}

Value::user_iterator mdv_users_end(Value *V) { return Value::user_iterator(); }
Value::user_iterator mdv_users_begin(Value *V) {
  if (auto *L = LocalAsMetadata::getIfExists(V)) {
    if (auto *MDV = MetadataAsValue::getIfExists(L->getContext(), L)) {
      return MDV->user_begin();
    }
  }
  return mdv_users_end(V);
}

static DbgValueInst *FindDbgValueInst(Value *Val) {
  for (auto it = mdv_users_begin(Val), end = mdv_users_end(Val); it != end;
       it++) {
    if (DbgValueInst *DbgValInst = dyn_cast<DbgValueInst>(*it))
      return DbgValInst;
  }
  return nullptr;
}

void MigrateDebugValue(Value *Old, Value *New) {
  DbgValueInst *DbgValInst = FindDbgValueInst(Old);
  if (DbgValInst == nullptr)
    return;

  DbgValInst->setOperand(
      0, MetadataAsValue::get(New->getContext(), ValueAsMetadata::get(New)));

  // Move the dbg value after the new instruction
  if (Instruction *NewInst = dyn_cast<Instruction>(New)) {
    if (NewInst->getNextNode() != DbgValInst) {
      DbgValInst->removeFromParent();
      DbgValInst->insertAfter(NewInst);
    }
  }
}

// Propagates any llvm.dbg.value instruction for a given vector
// to the elements that were used to create it through a series
// of insertelement instructions.
//
// This is used after lowering a vector-returning intrinsic.
// If we just keep the debug info on the recomposed vector,
// we will lose it when we break it apart again during later
// optimization stages.
void TryScatterDebugValueToVectorElements(Value *Val) {
  if (!isa<InsertElementInst>(Val) || !Val->getType()->isVectorTy())
    return;

  DbgValueInst *VecDbgValInst = FindDbgValueInst(Val);
  if (VecDbgValInst == nullptr)
    return;

  Type *ElemTy = Val->getType()->getVectorElementType();
  DIBuilder DbgInfoBuilder(*VecDbgValInst->getModule());
  unsigned ElemSizeInBits =
      VecDbgValInst->getModule()->getDataLayout().getTypeSizeInBits(ElemTy);

  DIExpression *ParentBitPiece = VecDbgValInst->getExpression();
  if (ParentBitPiece != nullptr && !ParentBitPiece->isBitPiece())
    ParentBitPiece = nullptr;

  while (InsertElementInst *InsertElt = dyn_cast<InsertElementInst>(Val)) {
    Value *NewElt = InsertElt->getOperand(1);
    unsigned EltIdx = static_cast<unsigned>(
        cast<ConstantInt>(InsertElt->getOperand(2))->getLimitedValue());
    unsigned OffsetInBits = EltIdx * ElemSizeInBits;

    if (ParentBitPiece) {
      assert(OffsetInBits + ElemSizeInBits <=
                 ParentBitPiece->getBitPieceSize() &&
             "Nested bit piece expression exceeds bounds of its parent.");
      OffsetInBits += ParentBitPiece->getBitPieceOffset();
    }

    DIExpression *DIExpr =
        DbgInfoBuilder.createBitPieceExpression(OffsetInBits, ElemSizeInBits);
    // Offset is basically unused and deprecated in later LLVM versions.
    // Emit it as zero otherwise later versions of the bitcode reader will drop
    // the intrinsic.
    DbgInfoBuilder.insertDbgValueIntrinsic(
        NewElt, /* Offset */ 0, VecDbgValInst->getVariable(), DIExpr,
        VecDbgValInst->getDebugLoc(), InsertElt);
    Val = InsertElt->getOperand(0);
  }
}

} // namespace dxilutil
} // namespace hlsl

///////////////////////////////////////////////////////////////////////////////

namespace {
class DxilLoadMetadata : public ModulePass {
public:
  static char ID; // Pass identification, replacement for typeid
  explicit DxilLoadMetadata() : ModulePass(ID) {}

  StringRef getPassName() const override {
    return "HLSL load DxilModule from metadata";
  }

  bool runOnModule(Module &M) override {
    if (!M.HasDxilModule()) {
      (void)M.GetOrCreateDxilModule();
      return true;
    }

    return false;
  }
};
} // namespace

char DxilLoadMetadata::ID = 0;

ModulePass *llvm::createDxilLoadMetadataPass() {
  return new DxilLoadMetadata();
}

INITIALIZE_PASS(DxilLoadMetadata, "hlsl-dxilload",
                "HLSL load DxilModule from metadata", false, false)