SPIRVLowerSPIRBlocks.cpp

//===- SPIRVLowerSPIRBlocks.cpp - Lower SPIR 2.0 blocks ---------*- C++ -*-===//
//
//                     The LLVM/SPIR-V Translator
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
// Copyright (c) 2014 Advanced Micro Devices, Inc. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal with the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimers.
// Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimers in the documentation
// and/or other materials provided with the distribution.
// Neither the names of Advanced Micro Devices, Inc., nor the names of its
// contributors may be used to endorse or promote products derived from this
// Software without specific prior written permission.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// THE SOFTWARE.
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file implements lowering of SPIR 2.0 blocks to functions.
///
//===----------------------------------------------------------------------===//

#include "OCLUtil.h"
#include "SPIRVInternal.h"

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
#include <iostream>
#include <list>
#include <memory>
#include <set>
#include <sstream>
#include <vector>

#define DEBUG_TYPE "spv-lower-spir-blocks"

using namespace llvm;
using namespace SPIRV;
using namespace OCLUtil;

namespace SPIRV {

/// Lower SPIR2 blocks to function calls.
///
/// SPIR2 representation of blocks:
///
/// block = spir_block_bind(bitcast(block_func), context_len, context_align,
///   context)
/// block_func_ptr = bitcast(spir_get_block_invoke(block))
/// context_ptr = spir_get_block_context(block)
/// ret = block_func_ptr(context_ptr, args)
///
/// Propagates block_func to each spir_get_block_invoke through def-use chain of
/// spir_block_bind, so that
/// ret = block_func(context, args)
class SPIRVLowerSPIRBlocks : public ModulePass {
public:
  SPIRVLowerSPIRBlocks() : ModulePass(ID), M(nullptr) {
    initializeSPIRVLowerSPIRBlocksPass(*PassRegistry::getPassRegistry());
  }

  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.addRequired<CallGraphWrapperPass>();
    AU.addRequired<AAResultsWrapperPass>();
    AU.addRequired<AssumptionCacheTracker>();
  }

  bool runOnModule(Module &Module) override {
    M = &Module;
    if (!lowerBlockBind()) {
      // There are no SPIR2 blocks in the module.
      return false;
    }
    lowerGetBlockInvoke();
    lowerGetBlockContext();
    eraseUselessGlobalVars();
    eliminateDeadArgs();
    erase(M->getFunction(SPIR_INTRINSIC_GET_BLOCK_INVOKE));
    erase(M->getFunction(SPIR_INTRINSIC_GET_BLOCK_CONTEXT));
    erase(M->getFunction(SPIR_INTRINSIC_BLOCK_BIND));
    LLVM_DEBUG(dbgs() << "------- After OCLLowerBlocks ------------\n"
                      << *M << '\n');
    return true;
  }

  static char ID;

private:
  const static int MaxIter = 1000;
  Module *M;

  bool lowerBlockBind() {
    auto F = M->getFunction(SPIR_INTRINSIC_BLOCK_BIND);
    if (!F)
      return false;
    int Iter = MaxIter;
    while (lowerBlockBind(F) && Iter > 0) {
      Iter--;
      LLVM_DEBUG(dbgs() << "-------------- after iteration " << MaxIter - Iter
                        << " --------------\n"
                        << *M << '\n');
    }
    assert(Iter > 0 && "Too many iterations");
    return true;
  }

  bool eraseUselessFunctions() {
    bool Changed = false;
    for (auto I = M->begin(), E = M->end(); I != E;) {
      Function *F = &(*I++);
      if (!GlobalValue::isInternalLinkage(F->getLinkage()) &&
          !F->isDeclaration())
        continue;

      dumpUsers(F, "[eraseUselessFunctions] ");
      for (auto UI = F->user_begin(), UE = F->user_end(); UI != UE;) {
        auto U = *UI++;
        if (auto CE = dyn_cast<ConstantExpr>(U)) {
          if (CE->use_empty()) {
            CE->dropAllReferences();
            Changed = true;
          }
        }
      }

      if (!F->use_empty()) {
        continue;
      }

      auto &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
      CallGraphNode *CGN = CG[F];

      if (CGN->getNumReferences() != 0) {
        continue;
      }

      erase(F);
      Changed = true;
    }
    return Changed;
  }

  void lowerGetBlockInvoke() {
    if (auto F = M->getFunction(SPIR_INTRINSIC_GET_BLOCK_INVOKE)) {
      for (auto UI = F->user_begin(), UE = F->user_end(); UI != UE;) {
        auto CI = dyn_cast<CallInst>(*UI++);
        assert(CI && "Invalid usage of spir_get_block_invoke");
        lowerGetBlockInvoke(CI);
      }
    }
  }

  void lowerGetBlockContext() {
    if (auto F = M->getFunction(SPIR_INTRINSIC_GET_BLOCK_CONTEXT)) {
      for (auto UI = F->user_begin(), UE = F->user_end(); UI != UE;) {
        auto CI = dyn_cast<CallInst>(*UI++);
        assert(CI && "Invalid usage of spir_get_block_context");
        lowerGetBlockContext(CI);
      }
    }
  }
  /// Lower calls of spir_block_bind.
  /// Return true if the Module is changed.
  bool lowerBlockBind(Function *BlockBindFunc) {
    bool Changed = false;
    for (auto I = BlockBindFunc->user_begin(), E = BlockBindFunc->user_end();
         I != E;) {
      LLVM_DEBUG(dbgs() << "[lowerBlockBind] " << **I << '\n');
      // Handle spir_block_bind(bitcast(block_func), context_len,
      // context_align, context)
      auto CallBlkBind = cast<CallInst>(*I++);
      Function *InvF = nullptr;
      Value *Ctx = nullptr;
      Value *CtxLen = nullptr;
      Value *CtxAlign = nullptr;
      getBlockInvokeFuncAndContext(CallBlkBind, &InvF, &Ctx, &CtxLen,
                                   &CtxAlign);
      assert(Ctx && "Invalid context");
      for (auto II = CallBlkBind->user_begin(), EE = CallBlkBind->user_end();
           II != EE;) {
        auto BlkUser = *II++;
        SPIRVDBG(dbgs() << "  Block user: " << *BlkUser << '\n');
        if (auto Ret = dyn_cast<ReturnInst>(BlkUser)) {
          bool Inlined = false;
          Changed |= lowerReturnBlock(Ret, CallBlkBind, Inlined);
          if (Inlined)
            return true;
        } else if (auto CI = dyn_cast<CallInst>(BlkUser)) {
          auto CallBindF = CI->getCalledFunction();
          auto Name = CallBindF->getName();
          StringRef DemangledName;
          if (Name == SPIR_INTRINSIC_GET_BLOCK_INVOKE) {
            assert(CI->getArgOperand(0) == CallBlkBind);
            Changed |= lowerGetBlockInvoke(CI, cast<Function>(InvF));
          } else if (Name == SPIR_INTRINSIC_GET_BLOCK_CONTEXT) {
            assert(CI->getArgOperand(0) == CallBlkBind);
            // Handle context_ptr = spir_get_block_context(block)
            lowerGetBlockContext(CI, Ctx);
            Changed = true;
          } else if (oclIsBuiltin(Name, DemangledName)) {
            lowerBlockBuiltin(CI, InvF, Ctx, CtxLen, CtxAlign, DemangledName);
            Changed = true;
          } else
            llvm_unreachable("Invalid block user");
        }
      }
      erase(CallBlkBind);
    }
    Changed |= eraseUselessFunctions();
    return Changed;
  }

  void lowerGetBlockContext(CallInst *CallGetBlkCtx, Value *Ctx = nullptr) {
    if (!Ctx)
      getBlockInvokeFuncAndContext(CallGetBlkCtx->getArgOperand(0), nullptr,
                                   &Ctx);
    assert(Ctx && "Invalid context");
    CallGetBlkCtx->replaceAllUsesWith(Ctx);
    LLVM_DEBUG(dbgs() << "  [lowerGetBlockContext] " << *CallGetBlkCtx << " => "
                      << *Ctx << "\n\n");
    erase(CallGetBlkCtx);
  }

  bool lowerGetBlockInvoke(CallInst *CallGetBlkInvoke,
                           Function *InvokeF = nullptr) {
    bool Changed = false;
    for (auto UI = CallGetBlkInvoke->user_begin(),
              UE = CallGetBlkInvoke->user_end();
         UI != UE;) {
      // Handle block_func_ptr = bitcast(spir_get_block_invoke(block))
      auto CallInv = cast<Instruction>(*UI++);
      auto Cast = dyn_cast<BitCastInst>(CallInv);
      if (Cast)
        CallInv = dyn_cast<Instruction>(*CallInv->user_begin());
      LLVM_DEBUG(dbgs() << "[lowerGetBlockInvoke]  " << *CallInv);
      // Handle ret = block_func_ptr(context_ptr, args)
      auto CI = cast<CallInst>(CallInv);
      auto F = CI->getCalledOperand();
      if (InvokeF == nullptr) {
        getBlockInvokeFuncAndContext(CallGetBlkInvoke->getArgOperand(0),
                                     &InvokeF, nullptr);
        assert(InvokeF);
      }
      assert(F->getType() == InvokeF->getType());
      CI->replaceUsesOfWith(F, InvokeF);
      LLVM_DEBUG(dbgs() << " => " << *CI << "\n\n");
      erase(Cast);
      Changed = true;
    }
    erase(CallGetBlkInvoke);
    return Changed;
  }

  void lowerBlockBuiltin(CallInst *CI, Function *InvF, Value *Ctx,
                         Value *CtxLen, Value *CtxAlign,
                         StringRef DemangledName) {
    mutateCallInstSPIRV(M, CI, [=](CallInst *CI, std::vector<Value *> &Args) {
      size_t I = 0;
      size_t E = Args.size();
      for (; I != E; ++I) {
        if (isPointerToOpaqueStructType(Args[I]->getType(),
                                        SPIR_TYPE_NAME_BLOCK_T)) {
          break;
        }
      }
      assert(I < E);
      Args[I] = castToVoidFuncPtr(InvF);
      if (I + 1 == E) {
        Args.push_back(Ctx);
        Args.push_back(CtxLen);
        Args.push_back(CtxAlign);
      } else {
        Args.insert(Args.begin() + I + 1, CtxAlign);
        Args.insert(Args.begin() + I + 1, CtxLen);
        Args.insert(Args.begin() + I + 1, Ctx);
      }
      if (DemangledName == kOCLBuiltinName::EnqueueKernel) {
        // Insert event arguments if there are not.
        if (!isa<IntegerType>(Args[3]->getType())) {
          Args.insert(Args.begin() + 3, getInt32(M, 0));
          Args.insert(Args.begin() + 4, getOCLNullClkEventPtr());
        }
        if (!isOCLClkEventPtrType(Args[5]->getType()))
          Args.insert(Args.begin() + 5, getOCLNullClkEventPtr());
      }
      return getSPIRVFuncName(OCLSPIRVBuiltinMap::map(DemangledName.str()));
    });
  }
  /// Transform return of a block.
  /// The function returning a block is inlined since the context cannot be
  /// passed to another function.
  /// Returns true of module is changed.
  bool lowerReturnBlock(ReturnInst *Ret, Value *CallBlkBind, bool &Inlined) {
    auto F = Ret->getParent()->getParent();
    auto Changed = false;
    for (auto UI = F->user_begin(), UE = F->user_end(); UI != UE;) {
      auto U = *UI++;
      dumpUsers(U);
      auto Inst = dyn_cast<Instruction>(U);
      if (Inst && Inst->use_empty()) {
        erase(Inst);
        Changed = true;
        continue;
      }
      auto CI = dyn_cast<CallInst>(U);
      if (!CI || CI->getCalledFunction() != F)
        continue;

      LLVM_DEBUG(dbgs() << "[lowerReturnBlock] inline " << F->getName()
                        << '\n');
      auto CG = &getAnalysis<CallGraphWrapperPass>().getCallGraph();
      auto ACT = &getAnalysis<AssumptionCacheTracker>();
      std::function<AssumptionCache &(Function &)> GetAssumptionCache =
          [&](Function &F) -> AssumptionCache & {
        return ACT->getAssumptionCache(F);
      };
      InlineFunctionInfo IFI(CG, GetAssumptionCache);
      InlineFunction(*cast<CallBase>(CI), IFI);
      Inlined = true;
    }
    return Changed || Inlined;
  }

  /// Looking for a global variables initialized by opencl.block*. If found,
  /// check
  /// its users. If users are trivially dead, erase them. If the global variable
  /// has no users left after that, erase it too.
  void eraseUselessGlobalVars() {
    std::vector<GlobalVariable *> GlobalVarsToDelete;
    for (GlobalVariable &G : M->globals()) {
      if (!G.hasInitializer())
        continue;
      Type *T = G.getInitializer()->getType();
      if (!T->isPointerTy())
        continue;
      T = cast<PointerType>(T)->getElementType();
      if (!T->isStructTy())
        continue;
      StringRef STName = cast<StructType>(T)->getName();
      if (STName != "opencl.block")
        continue;

      std::vector<User *> UsersToDelete;
      for (User *U : G.users())
        if (U->use_empty())
          UsersToDelete.push_back(U);
      for (User *U : UsersToDelete)
        erase(dyn_cast<Instruction>(U));

      if (G.use_empty()) {
        GlobalVarsToDelete.push_back(&G);
      }
    }
    for (GlobalVariable *G : GlobalVarsToDelete) {
      if (G->hasInitializer()) {
        Constant *Init = G->getInitializer();
        G->setInitializer(nullptr);
        if (llvm::isSafeToDestroyConstant(Init))
          Init->destroyConstant();
      }
      M->getGlobalList().erase(G);
    }
  }

  /// This method identifies F as an enqueued function iff:
  /// 1. F is bitcasted to a pointer, and
  /// 2. is passed to a function call of _Z21__spirv_EnqueueKernel
  /// Returns true if F is enqueued function, false otherwise.
  bool isEnqueuedFunction(Function &F) const {
    for (User *U : F.users()) {
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
        if (CE->getOpcode() != Instruction::BitCast)
          continue;
        if (!CE->getType()->isPointerTy())
          continue;
        // lowerBlockBind() should already have substituted last argument
        // of enqueue_kernel() call with arguments of spir_block_bind().
        for (User *UU : CE->users())
          if (CallInst *C = dyn_cast<CallInst>(UU))
            if (Function *CF = C->getCalledFunction())
              if (CF->getName().startswith("_Z21__spirv_EnqueueKernel"))
                return true;
      }
    }
    return false;
  }

  /// Looking for functions which first argument is i8* %.block_descriptor
  /// If users of this argument are dead, erase them.
  /// After that clone the found function, removing its first argument
  /// Then adjust all users/callers of the function with new arguments
  /// Implementation of this function is based on
  /// the dead argument elimination pass.
  void eliminateDeadArgs() {
    std::vector<Function *> FunctionsToDelete;
    for (Function &F : M->functions()) {
      if (F.arg_size() < 1)
        continue;
      auto FirstArg = F.arg_begin();
      if (FirstArg->getName() != ".block_descriptor")
        continue;

      // Skip the function if it is an enqueued kernel, because per SPIR-V spec,
      // function invoked with OpEnqueueKernel must have at least one argument
      // of type i8*
      if (isEnqueuedFunction(F))
        continue;

      std::vector<User *> UsersToDelete;
      for (User *U : FirstArg->users())
        if (U->use_empty())
          UsersToDelete.push_back(U);

      for (User *U : UsersToDelete)
        erase(dyn_cast<Instruction>(U));
      UsersToDelete.clear();

      if (!FirstArg->use_empty())
        continue;

      // Create new function without block descriptor argument.
      ValueToValueMapTy VMap;
      // If any of the arguments to the function are in the VMap,
      // the arguments are deleted from the resultant function.
      VMap[&*FirstArg] = llvm::UndefValue::get(FirstArg->getType());
      Function *NF = CloneFunction(&F, VMap);
      NF->takeName(&F);

      // Redirect all users of the old function to the new one.
      for (User *U : F.users()) {
        ConstantExpr *CE = dyn_cast<ConstantExpr>(U);
        if (CE && CE->getOpcode() == Instruction::BitCast) {
          Constant *NewCE = ConstantExpr::getBitCast(NF, CE->getType());
          U->replaceAllUsesWith(NewCE);
        } else if (auto *Call = dyn_cast<CallInst>(U)) {
          std::vector<Value *> Args;
          auto I = Call->arg_begin();
          Args.assign(++I, Call->arg_end()); // Skip first argument.
          CallInst *New = CallInst::Create(NF, Args, "", Call);
          assert(New->getType() == Call->getType());
          New->setCallingConv(Call->getCallingConv());
          New->setAttributes(NF->getAttributes());
          if (Call->isTailCall())
            New->setTailCall();
          New->setDebugLoc(Call->getDebugLoc());
          New->takeName(Call);
          Call->replaceAllUsesWith(New);
          UsersToDelete.push_back(Call);
        } else {
          llvm_unreachable("Unexpected user of function");
        }
      }
      for (User *U : UsersToDelete)
        erase(cast<Instruction>(U));
      UsersToDelete.clear();
      FunctionsToDelete.push_back(&F);
    } // iteration over module's functions.

    for (Function *F : FunctionsToDelete)
      erase(F);
  }

  void getBlockInvokeFuncAndContext(Value *Blk, Function **PInvF, Value **PCtx,
                                    Value **PCtxLen = nullptr,
                                    Value **PCtxAlign = nullptr) {
    Function *InvF = nullptr;
    Value *Ctx = nullptr;
    Value *CtxLen = nullptr;
    Value *CtxAlign = nullptr;
    if (auto CallBlkBind = dyn_cast<CallInst>(Blk)) {
      assert(CallBlkBind->getCalledFunction()->getName() ==
                 SPIR_INTRINSIC_BLOCK_BIND &&
             "Invalid block");
      InvF = dyn_cast<Function>(
          CallBlkBind->getArgOperand(0)->stripPointerCasts());
      CtxLen = CallBlkBind->getArgOperand(1);
      CtxAlign = CallBlkBind->getArgOperand(2);
      Ctx = CallBlkBind->getArgOperand(3);
    } else if (auto F = dyn_cast<Function>(Blk->stripPointerCasts())) {
      InvF = F;
      Ctx = Constant::getNullValue(IntegerType::getInt8PtrTy(M->getContext()));
    } else if (auto Load = dyn_cast<LoadInst>(Blk)) {
      auto Op = Load->getPointerOperand();
      if (auto GV = dyn_cast<GlobalVariable>(Op)) {
        if (GV->isConstant()) {
          InvF = cast<Function>(GV->getInitializer()->stripPointerCasts());
          Ctx = Constant::getNullValue(
              IntegerType::getInt8PtrTy(M->getContext()));
        } else {
          llvm_unreachable("load non-constant block?");
        }
      } else {
        llvm_unreachable("Loading block from non global?");
      }
    } else {
      llvm_unreachable("Invalid block");
    }
    LLVM_DEBUG(dbgs() << "  Block invocation func: " << InvF->getName() << '\n'
                      << "  Block context: " << *Ctx << '\n');
    assert(InvF && Ctx && "Invalid block");
    if (PInvF)
      *PInvF = InvF;
    if (PCtx)
      *PCtx = Ctx;
    if (PCtxLen)
      *PCtxLen = CtxLen;
    if (PCtxAlign)
      *PCtxAlign = CtxAlign;
  }
  void erase(Instruction *I) {
    if (!I)
      return;
    if (I->use_empty()) {
      I->dropAllReferences();
      I->eraseFromParent();
    } else
      dumpUsers(I);
  }
  void erase(ConstantExpr *I) {
    if (!I)
      return;
    if (I->use_empty()) {
      I->dropAllReferences();
      I->destroyConstant();
    } else
      dumpUsers(I);
  }
  void erase(Function *F) {
    if (!F)
      return;
    if (!F->use_empty()) {
      dumpUsers(F);
      return;
    }

    F->dropAllReferences();

    auto &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
    CallGraphNode *CGN = CG[F];

    if (CGN->getNumReferences() != 0) {
      return;
    }

    CGN->removeAllCalledFunctions();
    delete CG.removeFunctionFromModule(CGN);
  }

  llvm::PointerType *getOCLClkEventType() {
    return getOrCreateOpaquePtrType(M, SPIR_TYPE_NAME_CLK_EVENT_T,
                                    SPIRAS_Global);
  }

  llvm::PointerType *getOCLClkEventPtrType() {
    return PointerType::get(getOCLClkEventType(), SPIRAS_Generic);
  }

  bool isOCLClkEventPtrType(Type *T) {
    if (auto PT = dyn_cast<PointerType>(T))
      return isPointerToOpaqueStructType(PT->getElementType(),
                                         SPIR_TYPE_NAME_CLK_EVENT_T);
    return false;
  }

  llvm::Constant *getOCLNullClkEventPtr() {
    return Constant::getNullValue(getOCLClkEventPtrType());
  }

  void dumpGetBlockInvokeUsers(StringRef Prompt) {
    LLVM_DEBUG(dbgs() << Prompt);
    dumpUsers(M->getFunction(SPIR_INTRINSIC_GET_BLOCK_INVOKE));
  }
};

char SPIRVLowerSPIRBlocks::ID = 0;
} // namespace SPIRV

INITIALIZE_PASS_BEGIN(SPIRVLowerSPIRBlocks, "spv-lower-spir-blocks",
                      "SPIR-V lower SPIR blocks", false, false)
INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_END(SPIRVLowerSPIRBlocks, "spv-lower-spir-blocks",
                    "SPIR-V lower SPIR blocks", false, false)

ModulePass *llvm::createSPIRVLowerSPIRBlocks() {
  return new SPIRVLowerSPIRBlocks();
}