CGOpenMPRuntimeNVPTX.h

//===----- CGOpenMPRuntimeNVPTX.h - Interface to OpenMP NVPTX Runtimes ----===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This provides a class for OpenMP runtime code generation specialized to NVPTX
// targets.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_LIB_CODEGEN_CGOPENMPRUNTIMENVPTX_H
#define LLVM_CLANG_LIB_CODEGEN_CGOPENMPRUNTIMENVPTX_H

#include "CGOpenMPRuntime.h"
#include "CodeGenFunction.h"
#include "clang/AST/StmtOpenMP.h"
#include "llvm/IR/CallSite.h"

namespace clang {
namespace CodeGen {

class CGOpenMPRuntimeNVPTX : public CGOpenMPRuntime {
private:
  // Parallel outlined function work for workers to execute.
  llvm::SmallVector<llvm::Function *, 16> Work;

  struct EntryFunctionState {
    llvm::BasicBlock *ExitBB = nullptr;
  };

  class WorkerFunctionState {
  public:
    llvm::Function *WorkerFn;
    const CGFunctionInfo *CGFI;

    WorkerFunctionState(CodeGenModule &CGM);

  private:
    void createWorkerFunction(CodeGenModule &CGM);
  };

  bool isInSpmdExecutionMode() const;

  /// \brief Emit the worker function for the current target region.
  void emitWorkerFunction(WorkerFunctionState &WST);

  /// \brief Helper for worker function. Emit body of worker loop.
  void emitWorkerLoop(CodeGenFunction &CGF, WorkerFunctionState &WST);

  /// \brief Helper for generic target entry function. Guide the master and
  /// worker threads to their respective locations.
  void emitGenericEntryHeader(CodeGenFunction &CGF, EntryFunctionState &EST,
                              WorkerFunctionState &WST);

  /// \brief Signal termination of OMP execution for generic target entry
  /// function.
  void emitGenericEntryFooter(CodeGenFunction &CGF, EntryFunctionState &EST);

  /// \brief Helper for Spmd mode target directive's entry function.
  void emitSpmdEntryHeader(CodeGenFunction &CGF, EntryFunctionState &EST,
                           const OMPExecutableDirective &D);

  /// \brief Signal termination of Spmd mode execution.
  void emitSpmdEntryFooter(CodeGenFunction &CGF, EntryFunctionState &EST);

  /// \brief Returns specified OpenMP runtime function for the current OpenMP
  /// implementation.  Specialized for the NVPTX device.
  /// \param Function OpenMP runtime function.
  /// \return Specified function.
  llvm::Constant *createNVPTXRuntimeFunction(unsigned Function);

  //
  // Base class overrides.
  //

  /// \brief Creates offloading entry for the provided entry ID \a ID,
  /// address \a Addr, size \a Size, and flags \a Flags.
  void createOffloadEntry(llvm::Constant *ID, llvm::Constant *Addr,
                          uint64_t Size, int32_t Flags = 0) override;

  /// \brief Emit outlined function specialized for the Fork-Join
  /// programming model for applicable target directives on the NVPTX device.
  /// \param D Directive to emit.
  /// \param ParentName Name of the function that encloses the target region.
  /// \param OutlinedFn Outlined function value to be defined by this call.
  /// \param OutlinedFnID Outlined function ID value to be defined by this call.
  /// \param IsOffloadEntry True if the outlined function is an offload entry.
  /// An outlined function may not be an entry if, e.g. the if clause always
  /// evaluates to false.
  void emitGenericKernel(const OMPExecutableDirective &D, StringRef ParentName,
                         llvm::Function *&OutlinedFn,
                         llvm::Constant *&OutlinedFnID, bool IsOffloadEntry,
                         const RegionCodeGenTy &CodeGen);

  /// \brief Emit outlined function specialized for the Single Program
  /// Multiple Data programming model for applicable target directives on the
  /// NVPTX device.
  /// \param D Directive to emit.
  /// \param ParentName Name of the function that encloses the target region.
  /// \param OutlinedFn Outlined function value to be defined by this call.
  /// \param OutlinedFnID Outlined function ID value to be defined by this call.
  /// \param IsOffloadEntry True if the outlined function is an offload entry.
  /// \param CodeGen Object containing the target statements.
  /// An outlined function may not be an entry if, e.g. the if clause always
  /// evaluates to false.
  void emitSpmdKernel(const OMPExecutableDirective &D, StringRef ParentName,
                      llvm::Function *&OutlinedFn,
                      llvm::Constant *&OutlinedFnID, bool IsOffloadEntry,
                      const RegionCodeGenTy &CodeGen);

  /// \brief Emit outlined function for 'target' directive on the NVPTX
  /// device.
  /// \param D Directive to emit.
  /// \param ParentName Name of the function that encloses the target region.
  /// \param OutlinedFn Outlined function value to be defined by this call.
  /// \param OutlinedFnID Outlined function ID value to be defined by this call.
  /// \param IsOffloadEntry True if the outlined function is an offload entry.
  /// An outlined function may not be an entry if, e.g. the if clause always
  /// evaluates to false.
  void emitTargetOutlinedFunction(const OMPExecutableDirective &D,
                                  StringRef ParentName,
                                  llvm::Function *&OutlinedFn,
                                  llvm::Constant *&OutlinedFnID,
                                  bool IsOffloadEntry,
                                  const RegionCodeGenTy &CodeGen) override;

  /// \brief Emits code for parallel or serial call of the \a OutlinedFn with
  /// variables captured in a record which address is stored in \a
  /// CapturedStruct.
  /// This call is for the Generic Execution Mode.
  /// \param OutlinedFn Outlined function to be run in parallel threads. Type of
  /// this function is void(*)(kmp_int32 *, kmp_int32, struct context_vars*).
  /// \param CapturedVars A pointer to the record with the references to
  /// variables used in \a OutlinedFn function.
  /// \param IfCond Condition in the associated 'if' clause, if it was
  /// specified, nullptr otherwise.
  void emitGenericParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
                               llvm::Value *OutlinedFn,
                               ArrayRef<llvm::Value *> CapturedVars,
                               const Expr *IfCond);

  /// \brief Emits code for parallel or serial call of the \a OutlinedFn with
  /// variables captured in a record which address is stored in \a
  /// CapturedStruct.
  /// This call is for a parallel directive within an SPMD target directive.
  /// \param OutlinedFn Outlined function to be run in parallel threads. Type of
  /// this function is void(*)(kmp_int32 *, kmp_int32, struct context_vars*).
  /// \param CapturedVars A pointer to the record with the references to
  /// variables used in \a OutlinedFn function.
  /// \param IfCond Condition in the associated 'if' clause, if it was
  /// specified, nullptr otherwise.
  ///
  void emitSpmdParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
                            llvm::Value *OutlinedFn,
                            ArrayRef<llvm::Value *> CapturedVars,
                            const Expr *IfCond);

protected:
  /// \brief Get the function name of an outlined region.
  //  The name can be customized depending on the target.
  //
  StringRef getOutlinedHelperName() const override {
    return "__omp_outlined__";
  }

public:
  explicit CGOpenMPRuntimeNVPTX(CodeGenModule &CGM);

  /// \brief Emits call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32
  /// global_tid, kmp_int32 num_threads) to generate code for 'num_threads'
  /// clause.
  /// \param NumThreads An integer value of threads.
  virtual void emitNumThreadsClause(CodeGenFunction &CGF,
                                    llvm::Value *NumThreads,
                                    SourceLocation Loc) override;

  /// \brief This function ought to emit, in the general case, a call to
  // the openmp runtime kmpc_push_num_teams. In NVPTX backend it is not needed
  // as these numbers are obtained through the PTX grid and block configuration.
  /// \param NumTeams An integer expression of teams.
  /// \param ThreadLimit An integer expression of threads.
  void emitNumTeamsClause(CodeGenFunction &CGF, const Expr *NumTeams,
                          const Expr *ThreadLimit, SourceLocation Loc) override;

  /// \brief Emits inlined function for the specified OpenMP parallel
  //  directive.
  /// \a D. This outlined function has type void(*)(kmp_int32 *ThreadID,
  /// kmp_int32 BoundID, struct context_vars*).
  /// \param D OpenMP directive.
  /// \param ThreadIDVar Variable for thread id in the current OpenMP region.
  /// \param InnermostKind Kind of innermost directive (for simple directives it
  /// is a directive itself, for combined - its innermost directive).
  /// \param CodeGen Code generation sequence for the \a D directive.
  llvm::Value *
  emitParallelOutlinedFunction(const OMPExecutableDirective &D,
                               const VarDecl *ThreadIDVar,
                               OpenMPDirectiveKind InnermostKind,
                               const RegionCodeGenTy &CodeGen) override;

  /// \brief Emits inlined function for the specified OpenMP teams
  //  directive.
  /// \a D. This outlined function has type void(*)(kmp_int32 *ThreadID,
  /// kmp_int32 BoundID, struct context_vars*).
  /// \param D OpenMP directive.
  /// \param ThreadIDVar Variable for thread id in the current OpenMP region.
  /// \param InnermostKind Kind of innermost directive (for simple directives it
  /// is a directive itself, for combined - its innermost directive).
  /// \param CodeGen Code generation sequence for the \a D directive.
  llvm::Value *
  emitTeamsOutlinedFunction(const OMPExecutableDirective &D,
                            const VarDecl *ThreadIDVar,
                            OpenMPDirectiveKind InnermostKind,
                            const RegionCodeGenTy &CodeGen) override;

  /// \brief Emits code for teams call of the \a OutlinedFn with
  /// variables captured in a record which address is stored in \a
  /// CapturedStruct.
  /// \param OutlinedFn Outlined function to be run by team masters. Type of
  /// this function is void(*)(kmp_int32 *, kmp_int32, struct context_vars*).
  /// \param CapturedVars A pointer to the record with the references to
  /// variables used in \a OutlinedFn function.
  ///
  void emitTeamsCall(CodeGenFunction &CGF, const OMPExecutableDirective &D,
                     SourceLocation Loc, llvm::Value *OutlinedFn,
                     ArrayRef<llvm::Value *> CapturedVars) override;

  /// \brief Emits code for parallel or serial call of the \a OutlinedFn with
  /// variables captured in a record which address is stored in \a
  /// CapturedStruct.
  /// \param OutlinedFn Outlined function to be run in parallel threads. Type of
  /// this function is void(*)(kmp_int32 *, kmp_int32, struct context_vars*).
  /// \param CapturedVars A pointer to the record with the references to
  /// variables used in \a OutlinedFn function.
  /// \param IfCond Condition in the associated 'if' clause, if it was
  /// specified, nullptr otherwise.
  void emitParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
                        llvm::Value *OutlinedFn,
                        ArrayRef<llvm::Value *> CapturedVars,
                        const Expr *IfCond) override;

public:
  /// Target codegen is specialized based on two programming models: the
  /// 'generic' fork-join model of OpenMP, and a more GPU efficient 'spmd'
  /// model for constructs like 'target parallel' that support it.
  enum ExecutionMode {
    /// Single Program Multiple Data.
    Spmd,
    /// Generic codegen to support fork-join model.
    Generic,
    Unknown,
  };

private:
  // Track the execution mode when codegening directives within a target
  // region. The appropriate mode (generic/spmd) is set on entry to the
  // target region and used by containing directives such as 'parallel'
  // to emit optimized code.
  ExecutionMode CurrentExecutionMode;
};

} // CodeGen namespace.
} // clang namespace.

#endif // LLVM_CLANG_LIB_CODEGEN_CGOPENMPRUNTIMENVPTX_H