intel-graphics-compiler/IGC/Compiler/CISACodeGen/GenCodeGenModule.h

/*========================== begin_copyright_notice ============================

Copyright (C) 2017-2023 Intel Corporation

SPDX-License-Identifier: MIT

============================= end_copyright_notice ===========================*/

#pragma once
#include "Compiler/MetaDataApi/MetaDataApi.h"
#include "common/LLVMWarningsPush.hpp"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/CallGraph.h"
#include "common/LLVMWarningsPop.hpp"
#include "common/Types.hpp"
#include "Probe/Assertion.h"

namespace IGC {
class GenXFunctionGroupAnalysis;

/// \brief A module pass to initialize GenXFunctionGroupAnalysis and sort function
/// list in a module properly.
///
/// The module pass's results have two parts:
///
/// (1) GenXFunctionGroupAnalysis object, which stores information needed for vISA
///     emission. E.g, each non-empty function belongs to a uniquely defined
///     function group with a kernel function as the head.
///
/// (2) The module itself. All functions reachable from different function
///     groups will be cloned if necessary; they will be ordered such that each
///     callee will be after the caller in the module function list. When clone
///     happens, this module pass returns true, otherwise it returns false.
///     Currently, we assume no kernel functions will be called. This
///     requirement could be enforced before this pass by inlining kernels.
///
class GenXCodeGenModule : public llvm::ModulePass {
public:
  static char ID;
  GenXCodeGenModule();
  ~GenXCodeGenModule();

  GenXCodeGenModule(const GenXCodeGenModule &) = delete;
  GenXCodeGenModule &operator=(const GenXCodeGenModule &) = delete;

  virtual llvm::StringRef getPassName() const override { return "GenX CodeGen module"; }
  void getAnalysisUsage(llvm::AnalysisUsage &AU) const override;
  bool runOnModule(llvm::Module &M) override;

private:
  void processFunction(llvm::Function &F);
  void processSCC(std::vector<llvm::CallGraphNode *> *SCCNodes);
  void setFuncProperties(llvm::CallGraph &CG);
  void copyFuncProperties(llvm::Function *To, llvm::Function *From);

  GenXFunctionGroupAnalysis *FGA;
  IGC::IGCMD::MetaDataUtils *pMdUtils;
  bool Modified;
  unsigned m_FunctionCloningThreshold = 0;

  // Find the set of functions that cannot be promoted to indirect, must be cloned
  void detectUnpromotableFunctions(llvm::Module *pM);
  std::set<llvm::Function *> m_UnpromotableFuncs;
};

/// \brief A collection of functions that are reachable from a kernel.
class FunctionGroup {
public:
  friend class GenXFunctionGroupAnalysis;
  /// \brief use 2-d vector of Functions to represent FunctionGroup.
  /// Each sub-vector is a subgroup led by a kernel or a stack-call function.
  /// Element [0][0] is the group head. Element[i][0] is the sub-group head.
  typedef llvm::SmallVector<llvm::AssertingVH<llvm::Function>, 8> SubGroupContainer;
  typedef llvm::SmallVector<SubGroupContainer *, 4> FunctionGroupContainer;
  FunctionGroupContainer Functions;

  class iterator {
  public:
    enum POS { BEGIN, END };
    iterator(FunctionGroupContainer &FC, POS pos) {
      if (pos == BEGIN) {
        major = FC.begin();
        majorEnd = FC.end();
        minor = (*major)->begin();
      } else if (pos == END) {
        major = FC.end();
        majorEnd = FC.end();
        minor = FC.back()->end();
      }
    }
    iterator &operator++() {
      minor++;
      if (minor == (*major)->end()) {
        major++;
        if (major != majorEnd)
          minor = (*major)->begin();
      }
      return *this;
    }
    llvm::Function *operator*() { return *minor; }
    bool operator==(const iterator &rhs) const { return (major == rhs.major && minor == rhs.minor); }
    bool operator!=(const iterator &rhs) const { return !(*this == rhs); }

  private:
    FunctionGroupContainer::iterator major;
    FunctionGroupContainer::iterator majorEnd;
    SubGroupContainer::iterator minor;
  };

  iterator begin() { return iterator(Functions, iterator::BEGIN); }
  iterator end() { return iterator(Functions, iterator::END); }

  ~FunctionGroup() {
    for (auto F : Functions) {
      delete F;
    }
  }
  FunctionGroup() = default;
  FunctionGroup(const FunctionGroup &) = delete;
  FunctionGroup &operator=(const FunctionGroup &) = delete;

  /// \brief The entry kernel function of group.
  llvm::Function *getHead() const { return Functions.front()->front(); }
  /// \brief The tail function of a group.
  llvm::Function *back() const { return Functions.back()->back(); }
  /// \brief Only one function in this group
  bool isSingle() const { return (Functions.size() == 1 && Functions.front()->size() == 1); }
  /// \brief Only one function in this group ignoring stack overflow detection methods
  bool isSingleIgnoringStackOverflowDetection() const {
    auto isNotStackOverflowDetection = [](const llvm::Function *F) {
      return !F->getName().startswith("__stackoverflow_detection") && !F->getName().startswith("__stackoverflow_init");
    };
    return (Functions.size() == 1 &&
            std::count_if(Functions.front()->begin(), Functions.front()->end(), isNotStackOverflowDetection) == 1);
  }
  /// \brief Function group has a subroutine
  bool hasSubroutine() const { return m_hasSubroutine; }
  /// \brief Function group has a stack call (including indirect calls)
  bool hasStackCall() const { return m_hasStackCall; }
  bool hasInlineAsm() const { return m_hasInlineAsm; }
  /// \brief Function group has a variable length alloca
  bool hasVariableLengthAlloca() const { return m_hasVariableLengthAlloca; }
  /// \brief Function group has indirect calls (i.e. calls functions in the Indirect Function Group)
  bool hasIndirectCall() const { return m_hasIndirectCall; }
  /// \brief Function group has nested calls
  bool hasNestedCall() const { return m_hasNestedCall; }
  /// \brief Function group has indirect calls where the full CG is not available (e.g. calls function pointer, or
  /// callees in external module)
  bool hasPartialCallGraph() const { return m_hasPartialCallGraph; }
  /// \brief Function group has recursion
  bool hasRecursion() const { return m_hasRecursion; }

  void replaceGroupHead(llvm::Function *OH, llvm::Function *NH) {
    IGC_UNUSED(OH);
    auto headSG = Functions[0];
    llvm::AssertingVH<llvm::Function> &HVH = (*headSG)[0];
    IGC_ASSERT_MESSAGE(&(*HVH) == OH, "Group's head isn't set up correctly!");
    HVH = NH;
  }

  // For a single FG, an SIMD mode is valid only if SIMD modes of all
  // functions in that group are valid.
  bool checkSimdModeValid(SIMDMode Mode) const;
  void setSimdModeInvalid(SIMDMode Mode);

private:
  bool m_hasSubroutine = false;
  bool m_hasStackCall = false;
  bool m_hasInlineAsm = false;
  bool m_hasVariableLengthAlloca = false;
  bool m_hasIndirectCall = false;
  bool m_hasRecursion = false;
  bool m_hasNestedCall = false;
  bool m_hasPartialCallGraph = false;
  bool SIMDModeValid[3] = {true, true, true};
};

class GenXFunctionGroupAnalysis : public llvm::ImmutablePass {
  enum class FuncPropertyInfo : uint32_t {
    FPI_LEAF = 0x1 // bit 0:  1 (leaf function)
  };

  /// \brief The module being analyzed.
  llvm::Module *M;

  /// \brief Function groups constructed in this module.
  llvm::SmallVector<FunctionGroup *, 8> Groups;

  /// \brief Each function belongs to a uniquely defined function group.
  llvm::DenseMap<const llvm::Function *, FunctionGroup *> GroupMap;

  /// \brief Each function also belongs to a uniquely defined sub-group of a stack-call entry
  llvm::DenseMap<const llvm::Function *, llvm::Function *> SubGroupMap;

  /// \brief Properties for each function
  llvm::DenseMap<const llvm::Function *, uint32_t> FuncProperties;

  /// \brief Special group that contains all indirect call functions
  /// SIMD variants stored with SIMD8 in idx 0, SIMD16 in idx 1, SIMD32 in idx 2
  llvm::SmallVector<FunctionGroup *, 3> IndirectCallGroup{nullptr, nullptr, nullptr};

public:
  static char ID;
  explicit GenXFunctionGroupAnalysis();
  ~GenXFunctionGroupAnalysis() { clear(); }
  GenXFunctionGroupAnalysis(const GenXFunctionGroupAnalysis &) = delete;
  GenXFunctionGroupAnalysis &operator=(const GenXFunctionGroupAnalysis &) = delete;

  virtual llvm::StringRef getPassName() const override { return "FunctionGroup analysis"; }

  /// This function returns nullptr if no analysis is not available.
  llvm::Module *getModule() { return M; }
  void setModule(llvm::Module *Mod) { M = Mod; }
  void clear();

  /// \brief This function rebuilds function groups with the assumption that
  /// no function will be directly or undirectly called from more than one
  /// kernel, and functions in the module are well-ordered. It returns false if
  /// fails to rebuild and returns true otherwise.
  ///
  bool rebuild(llvm::Module *Mod);

  // Attach all indirectly called functions to a single kernel group
  void addIndirectFuncsToKernelGroup(llvm::Module *pModule);

  // Replace OF with NF in Groups and GroupMap
  void replaceEntryFunc(llvm::Function *OF, llvm::Function *NF);

  /// \brief Verify if this analysis result is valid.
  bool verify();

  void getAnalysisUsage(llvm::AnalysisUsage &AU) const override;

  /// \brief Get the FunctionGroup containing Function F, else nullptr.
  FunctionGroup *getGroup(const llvm::Function *F);

  /// \brief Get the FunctionGroup for which Function F is the head, else
  /// nullptr.
  FunctionGroup *getGroupForHead(const llvm::Function *F);

  /// \brief Get the group head for the group to which F belongs.
  llvm::Function *getGroupHead(const llvm::Function *F) {
    auto FG = getGroup(F);
    IGC_ASSERT(nullptr != FG);
    return FG->getHead();
  }
  /// \brief Get the subgroup head for the subgroup to which F belongs
  llvm::Function *getSubGroupMap(llvm::Function *F) {
    auto I = SubGroupMap.find(F);
    if (I == SubGroupMap.end())
      return nullptr;
    return I->second;
  }

  void setSubGroupMap(llvm::Function *F, llvm::Function *SubGroupHead) { SubGroupMap[F] = SubGroupHead; }

  bool isIndirectCallGroup(const FunctionGroup *FG) {
    for (auto ICG : IndirectCallGroup) {
      if (FG && FG == ICG)
        return true;
    }
    return false;
  }

  bool isIndirectCallGroup(const llvm::Function *F) {
    IGC_ASSERT(F);
    FunctionGroup *FG = getGroup(F);
    return isIndirectCallGroup(FG);
  }

  /// \brief Check whether this is a group header.
  bool isGroupHead(const llvm::Function *F) { return getGroupForHead(F) != nullptr; }

  /// \brief Check whether this is the last function in a function group. This
  /// order is also reflected in the module function list.
  bool isGroupTail(const llvm::Function *F) {
    FunctionGroup *FG = getGroup(F);
    IGC_ASSERT_MESSAGE(nullptr != FG, "not in function group");
    return F == FG->back();
  }

  bool isLeafFunc(const llvm::Function *F) {
    auto FI = FuncProperties.find(F);
    if (FI != FuncProperties.end()) {
      return (FI->second & (uint32_t)FuncPropertyInfo::FPI_LEAF);
    }
    return false;
  }
  void setLeafFunc(const llvm::Function *F) {
    auto II = FuncProperties.find(F);
    uint32_t P = (II != FuncProperties.end()) ? II->second : 0;
    FuncProperties[F] = (P | (uint32_t)FuncPropertyInfo::FPI_LEAF);
  }
  void copyFuncProperties(const llvm::Function *To, const llvm::Function *From) {
    auto II = FuncProperties.find(From);
    if (II != FuncProperties.end()) {
      FuncProperties[To] = II->second;
    }
  }

  /// get or create the function group that holds all indirectly-called functions
  FunctionGroup *getOrCreateIndirectCallGroup(llvm::Module *pModule, int SimdSize = 0);

  /// for multi SIMD variant compilation, clone functions from the default dummy kernel group
  /// into the SIMD variant version of the dummy kernel.
  void CloneFunctionGroupForMultiSIMDCompile(llvm::Module *pModule);

  /// check if function is stack-called
  bool useStackCall(llvm::Function *F);

  /// sets function group attribute flags
  void setGroupAttributes();

  typedef llvm::SmallVectorImpl<FunctionGroup *>::iterator iterator;
  iterator begin() { return iterator(Groups.begin()); }
  iterator end() { return iterator(Groups.end()); }

  /// \brief Returns the number of groups, aka. kernels.
  size_t size() { return Groups.size(); }

  /// \brife add Function F to FunctionGroup FG.
  void addToFunctionGroup(llvm::Function *F, FunctionGroup *FG, llvm::Function *SubGrpH);

  /// \brief Create a new FunctionGroup with head F.
  FunctionGroup *createFunctionGroup(llvm::Function *F);

  void print(llvm::raw_ostream &os);

#if defined(_DEBUG)
  void dump();
#endif
};

llvm::ModulePass *createGenXCodeGenModulePass();
llvm::ImmutablePass *createGenXFunctionGroupAnalysisPass();
llvm::Pass *createSubroutineInlinerPass();

} // namespace IGC