ModuleTranslation.h

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//===- ModuleTranslation.h - MLIR to LLVM conversion ------------*- 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 implements the translation between an MLIR LLVM dialect module and
// the corresponding LLVMIR module. It only handles core LLVM IR operations.
//
//===----------------------------------------------------------------------===//

#ifndef MLIR_TARGET_LLVMIR_MODULETRANSLATION_H
#define MLIR_TARGET_LLVMIR_MODULETRANSLATION_H

#include "mlir/IR/Operation.h"
#include "mlir/IR/Value.h"
#include "mlir/Target/LLVMIR/Export.h"
#include "mlir/Target/LLVMIR/LLVMTranslationInterface.h"
#include "mlir/Target/LLVMIR/TypeToLLVM.h"

#include "llvm/ADT/SetVector.h"
#include "llvm/Frontend/OpenMP/OMPIRBuilder.h"

namespace llvm {
class BasicBlock;
class IRBuilderBase;
class Function;
class Value;
} // namespace llvm

namespace mlir {
class Attribute;
class Block;
class Location;

namespace LLVM {

namespace detail {
class DebugTranslation;
} // end namespace detail

class LLVMFuncOp;

/// Implementation class for module translation. Holds a reference to the module
/// being translated, and the mappings between the original and the translated
/// functions, basic blocks and values. It is practically easier to hold these
/// mappings in one class since the conversion of control flow operations
/// needs to look up block and function mappings.
class ModuleTranslation {
  friend std::unique_ptr<llvm::Module>
  mlir::translateModuleToLLVMIR(Operation *, llvm::LLVMContext &, StringRef);

public:
  /// Stores the mapping between a function name and its LLVM IR representation.
  void mapFunction(StringRef name, llvm::Function *func) {
    auto result = functionMapping.try_emplace(name, func);
    (void)result;
    assert(result.second &&
           "attempting to map a function that is already mapped");
  }

  /// Finds an LLVM IR function by its name.
  llvm::Function *lookupFunction(StringRef name) const {
    return functionMapping.lookup(name);
  }

  /// Stores the mapping between an MLIR value and its LLVM IR counterpart.
  void mapValue(Value mlir, llvm::Value *llvm) { mapValue(mlir) = llvm; }

  /// Provides write-once access to store the LLVM IR value corresponding to the
  /// given MLIR value.
  llvm::Value *&mapValue(Value value) {
    llvm::Value *&llvm = valueMapping[value];
    assert(llvm == nullptr &&
           "attempting to map a value that is already mapped");
    return llvm;
  }

  /// Finds an LLVM IR value corresponding to the given MLIR value.
  llvm::Value *lookupValue(Value value) const {
    return valueMapping.lookup(value);
  }

  /// Looks up remapped a list of remapped values.
  SmallVector<llvm::Value *> lookupValues(ValueRange values);

  /// Stores the mapping between an MLIR block and LLVM IR basic block.
  void mapBlock(Block *mlir, llvm::BasicBlock *llvm) {
    auto result = blockMapping.try_emplace(mlir, llvm);
    (void)result;
    assert(result.second && "attempting to map a block that is already mapped");
  }

  /// Finds an LLVM IR basic block that corresponds to the given MLIR block.
  llvm::BasicBlock *lookupBlock(Block *block) const {
    return blockMapping.lookup(block);
  }

  /// Stores the mapping between an MLIR operation with successors and a
  /// corresponding LLVM IR instruction.
  void mapBranch(Operation *mlir, llvm::Instruction *llvm) {
    auto result = branchMapping.try_emplace(mlir, llvm);
    (void)result;
    assert(result.second &&
           "attempting to map a branch that is already mapped");
  }

  /// Finds an LLVM IR instruction that corresponds to the given MLIR operation
  /// with successors.
  llvm::Instruction *lookupBranch(Operation *op) const {
    return branchMapping.lookup(op);
  }

  /// Removes the mapping for blocks contained in the region and values defined
  /// in these blocks.
  void forgetMapping(Region &region);

  /// Returns the LLVM metadata corresponding to a reference to an mlir LLVM
  /// dialect access group operation.
  llvm::MDNode *getAccessGroup(Operation &opInst,
                               SymbolRefAttr accessGroupRef) const;

  /// Returns the LLVM metadata corresponding to a reference to an mlir LLVM
  /// dialect alias scope operation
  llvm::MDNode *getAliasScope(Operation &opInst,
                              SymbolRefAttr aliasScopeRef) const;

  /// Returns the LLVM metadata corresponding to a llvm loop's codegen
  /// options attribute.
  llvm::MDNode *lookupLoopOptionsMetadata(Attribute options) const {
    return loopOptionsMetadataMapping.lookup(options);
  }

  void mapLoopOptionsMetadata(Attribute options, llvm::MDNode *metadata) {
    auto result = loopOptionsMetadataMapping.try_emplace(options, metadata);
    (void)result;
    assert(result.second &&
           "attempting to map loop options that was already mapped");
  }

  // Sets LLVM metadata for memory operations that are in a parallel loop.
  void setAccessGroupsMetadata(Operation *op, llvm::Instruction *inst);

  // Sets LLVM metadata for memory operations that have alias scope information.
  void setAliasScopeMetadata(Operation *op, llvm::Instruction *inst);

  /// Converts the type from MLIR LLVM dialect to LLVM.
  llvm::Type *convertType(Type type);

  /// Returns the MLIR context of the module being translated.
  MLIRContext &getContext() { return *mlirModule->getContext(); }

  /// Returns the LLVM context in which the IR is being constructed.
  llvm::LLVMContext &getLLVMContext() const { return llvmModule->getContext(); }

  /// Finds an LLVM IR global value that corresponds to the given MLIR operation
  /// defining a global value.
  llvm::GlobalValue *lookupGlobal(Operation *op) {
    return globalsMapping.lookup(op);
  }

  /// Returns the OpenMP IR builder associated with the LLVM IR module being
  /// constructed.
  llvm::OpenMPIRBuilder *getOpenMPBuilder() {
    if (!ompBuilder) {
      ompBuilder = std::make_unique<llvm::OpenMPIRBuilder>(*llvmModule);
      ompBuilder->initialize();
    }
    return ompBuilder.get();
  }

  /// Translates the given location.
  const llvm::DILocation *translateLoc(Location loc, llvm::DILocalScope *scope);

  /// Translates the contents of the given block to LLVM IR using this
  /// translator. The LLVM IR basic block corresponding to the given block is
  /// expected to exist in the mapping of this translator. Uses `builder` to
  /// translate the IR, leaving it at the end of the block. If `ignoreArguments`
  /// is set, does not produce PHI nodes for the block arguments. Otherwise, the
  /// PHI nodes are constructed for block arguments but are _not_ connected to
  /// the predecessors that may not exist yet.
  LogicalResult convertBlock(Block &bb, bool ignoreArguments,
                             llvm::IRBuilderBase &builder);

  /// Gets the named metadata in the LLVM IR module being constructed, creating
  /// it if it does not exist.
  llvm::NamedMDNode *getOrInsertNamedModuleMetadata(StringRef name);

  /// Common CRTP base class for ModuleTranslation stack frames.
  class StackFrame {
  public:
    virtual ~StackFrame() {}
    TypeID getTypeID() const { return typeID; }

  protected:
    explicit StackFrame(TypeID typeID) : typeID(typeID) {}

  private:
    const TypeID typeID;
    virtual void anchor();
  };

  /// Concrete CRTP base class for ModuleTranslation stack frames. When
  /// translating operations with regions, users of ModuleTranslation can store
  /// state on ModuleTranslation stack before entering the region and inspect
  /// it when converting operations nested within that region. Users are
  /// expected to derive this class and put any relevant information into fields
  /// of the derived class. The usual isa/dyn_cast functionality is available
  /// for instances of derived classes.
  template <typename Derived>
  class StackFrameBase : public StackFrame {
  public:
    explicit StackFrameBase() : StackFrame(TypeID::get<Derived>()) {}
  };

  /// Creates a stack frame of type `T` on ModuleTranslation stack. `T` must
  /// be derived from `StackFrameBase<T>` and constructible from the provided
  /// arguments. Doing this before entering the region of the op being
  /// translated makes the frame available when translating ops within that
  /// region.
  template <typename T, typename... Args>
  void stackPush(Args &&...args) {
    static_assert(
        std::is_base_of<StackFrame, T>::value,
        "can only push instances of StackFrame on ModuleTranslation stack");
    stack.push_back(std::make_unique<T>(std::forward<Args>(args)...));
  }

  /// Pops the last element from the ModuleTranslation stack.
  void stackPop() { stack.pop_back(); }

  /// Calls `callback` for every ModuleTranslation stack frame of type `T`
  /// starting from the top of the stack.
  template <typename T>
  WalkResult
  stackWalk(llvm::function_ref<WalkResult(const T &)> callback) const {
    static_assert(std::is_base_of<StackFrame, T>::value,
                  "expected T derived from StackFrame");
    if (!callback)
      return WalkResult::skip();
    for (const std::unique_ptr<StackFrame> &frame : llvm::reverse(stack)) {
      if (T *ptr = dyn_cast_or_null<T>(frame.get())) {
        WalkResult result = callback(*ptr);
        if (result.wasInterrupted())
          return result;
      }
    }
    return WalkResult::advance();
  }

  /// RAII object calling stackPush/stackPop on construction/destruction.
  template <typename T>
  struct SaveStack {
    template <typename... Args>
    explicit SaveStack(ModuleTranslation &m, Args &&...args)
        : moduleTranslation(m) {
      moduleTranslation.stackPush<T>(std::forward<Args>(args)...);
    }
    ~SaveStack() { moduleTranslation.stackPop(); }

  private:
    ModuleTranslation &moduleTranslation;
  };

private:
  ModuleTranslation(Operation *module,
                    std::unique_ptr<llvm::Module> llvmModule);
  ~ModuleTranslation();

  /// Converts individual components.
  LogicalResult convertOperation(Operation &op, llvm::IRBuilderBase &builder);
  LogicalResult convertFunctionSignatures();
  LogicalResult convertFunctions();
  LogicalResult convertGlobals();
  LogicalResult convertOneFunction(LLVMFuncOp func);

  /// Process access_group LLVM Metadata operations and create LLVM
  /// metadata nodes.
  LogicalResult createAccessGroupMetadata();

  /// Process alias.scope LLVM Metadata operations and create LLVM
  /// metadata nodes for them and their domains.
  LogicalResult createAliasScopeMetadata();

  /// Translates dialect attributes attached to the given operation.
  LogicalResult convertDialectAttributes(Operation *op);

  /// Original and translated module.
  Operation *mlirModule;
  std::unique_ptr<llvm::Module> llvmModule;
  /// A converter for translating debug information.
  std::unique_ptr<detail::DebugTranslation> debugTranslation;

  /// Builder for LLVM IR generation of OpenMP constructs.
  std::unique_ptr<llvm::OpenMPIRBuilder> ompBuilder;

  /// Mappings between llvm.mlir.global definitions and corresponding globals.
  DenseMap<Operation *, llvm::GlobalValue *> globalsMapping;

  /// A stateful object used to translate types.
  TypeToLLVMIRTranslator typeTranslator;

  /// A dialect interface collection used for dispatching the translation to
  /// specific dialects.
  LLVMTranslationInterface iface;

  /// Mappings between original and translated values, used for lookups.
  llvm::StringMap<llvm::Function *> functionMapping;
  DenseMap<Value, llvm::Value *> valueMapping;
  DenseMap<Block *, llvm::BasicBlock *> blockMapping;

  /// A mapping between MLIR LLVM dialect terminators and LLVM IR terminators
  /// they are converted to. This allows for connecting PHI nodes to the source
  /// values after all operations are converted.
  DenseMap<Operation *, llvm::Instruction *> branchMapping;

  /// Mapping from an access group metadata operation to its LLVM metadata.
  /// This map is populated on module entry and is used to annotate loops (as
  /// identified via their branches) and contained memory accesses.
  DenseMap<Operation *, llvm::MDNode *> accessGroupMetadataMapping;

  /// Mapping from an attribute describing loop codegen options to its LLVM
  /// metadata. The metadata is attached to Latch block branches with this
  /// attribute.
  DenseMap<Attribute, llvm::MDNode *> loopOptionsMetadataMapping;

  /// Mapping from an access scope metadata operation to its LLVM metadata.
  /// This map is populated on module entry.
  DenseMap<Operation *, llvm::MDNode *> aliasScopeMetadataMapping;

  /// Stack of user-specified state elements, useful when translating operations
  /// with regions.
  SmallVector<std::unique_ptr<StackFrame>> stack;
};

namespace detail {
/// For all blocks in the region that were converted to LLVM IR using the given
/// ModuleTranslation, connect the PHI nodes of the corresponding LLVM IR blocks
/// to the results of preceding blocks.
void connectPHINodes(Region &region, const ModuleTranslation &state);

/// Get a topologically sorted list of blocks of the given region.
SetVector<Block *> getTopologicallySortedBlocks(Region &region);

/// Create an LLVM IR constant of `llvmType` from the MLIR attribute `attr`.
/// This currently supports integer, floating point, splat and dense element
/// attributes and combinations thereof. Also, an array attribute with two
/// elements is supported to represent a complex constant.  In case of error,
/// report it to `loc` and return nullptr.
llvm::Constant *getLLVMConstant(llvm::Type *llvmType, Attribute attr,
                                Location loc,
                                const ModuleTranslation &moduleTranslation,
                                bool isTopLevel = true);

/// Creates a call to an LLVM IR intrinsic function with the given arguments.
llvm::Value *createIntrinsicCall(llvm::IRBuilderBase &builder,
                                 llvm::Intrinsic::ID intrinsic,
                                 ArrayRef<llvm::Value *> args = {},
                                 ArrayRef<llvm::Type *> tys = {});
} // namespace detail

} // namespace LLVM
} // namespace mlir

namespace llvm {
template <typename T>
struct isa_impl<T, ::mlir::LLVM::ModuleTranslation::StackFrame> {
  static inline bool
  doit(const ::mlir::LLVM::ModuleTranslation::StackFrame &frame) {
    return frame.getTypeID() == ::mlir::TypeID::get<T>();
  }
};
} // namespace llvm

#endif // MLIR_TARGET_LLVMIR_MODULETRANSLATION_H