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/*========================== begin_copyright_notice ============================
Copyright (C) 2019-2021 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
#include "Compiler/IGCPassSupport.h"
#include "Compiler/Optimizer/IndirectCallOptimization.hpp"
#include "Compiler/CodeGenPublic.h"
#include "common/IGCIRBuilder.h"
#include "common/LLVMWarningsPush.hpp"
#include <llvmWrapper/IR/Instructions.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/InstIterator.h>
#include <llvm/Transforms/Utils/BasicBlockUtils.h>
#include "common/LLVMWarningsPop.hpp"
#include <map>
#include "Probe/Assertion.h"
using namespace llvm;
#define PASS_FLAG "indirect-call-optimization"
#define PASS_DESCRIPTION "Changes indirect calls to direct calls if possible"
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
namespace IGC
{
// Register pass to igc-opt
IGC_INITIALIZE_PASS_BEGIN(IndirectCallOptimization, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
IGC_INITIALIZE_PASS_END(IndirectCallOptimization, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
char IndirectCallOptimization::ID = 0;
IndirectCallOptimization::IndirectCallOptimization() : FunctionPass(ID)
{
initializeIndirectCallOptimizationPass(*PassRegistry::getPassRegistry());
}
bool IndirectCallOptimization::runOnFunction(Function& F)
{
bool modified = false;
auto BI = F.begin(), BE = F.end();
for (; BI != BE; BI++)
{
auto II = BI->begin(), IE = BI->end();
while (II != IE)
{
if (CallInst* call = dyn_cast<CallInst>(&*II))
{
if (visitCallInst(*call))
{
// Iterators have been invalidated, so we need to update them
II = call->getNextNode()->getIterator();
IE = call->getParent()->getTerminator()->getIterator();
BI = call->getParent()->getIterator();
BE = F.end();
call->eraseFromParent();
modified = true;
continue;
}
}
II++;
}
}
return modified;
}
inline bool CompareCallFuncSignature(CallInst* call, Function* func)
{
if (func->getReturnType() != call->getType())
return false;
if (func->arg_size() != IGCLLVM::getNumArgOperands(call))
return false;
unsigned index = 0;
for (auto ai = func->arg_begin(), ei = func->arg_end(); ai != ei; ai++)
{
if (ai->getType() != call->getArgOperand(index++)->getType())
{
return false;
}
}
return true;
}
bool IndirectCallOptimization::visitCallInst(CallInst &CI)
{
// Not an indirect call
if (CI.getCalledFunction() || CI.isInlineAsm()) return false;
Function* currFunc = CI.getParent()->getParent();
Module* pModule = currFunc->getParent();
SmallSet<Function*, 8> CallableFuncs;
// function groups are stored in the !callees metadata
if (MDNode* callmd = CI.getMetadata("callees"))
{
for (auto& op : callmd->operands())
{
if (Function* F = mdconst::dyn_extract<Function>(op))
{
if (F->hasFnAttribute("referenced-indirectly") && CompareCallFuncSignature(&CI, F))
{
CallableFuncs.insert(F);
continue;
}
}
IGC_ASSERT_MESSAGE(0, "Invalid function in function group!");
return false;
}
}
if (CallableFuncs.empty())
{
// Nothing to do
return false;
}
else if (CallableFuncs.size() == 1)
{
// Trivial case, replace with the direct call
Function* F = *CallableFuncs.begin();
SmallVector<Value*, 8> callArgs(CI.arg_begin(), CI.arg_end());
IGCIRBuilder<> IRB(pModule->getContext());
IRB.SetInsertPoint(&CI);
CallInst* dirCall = IRB.CreateCall(F, callArgs);
CI.replaceAllUsesWith(dirCall);
return true;
}
// Add some checks to determine if inlining is profitable
// Limit the number of branches
if (CallableFuncs.size() > 4)
return false;
// Limit max number of instructions added after inlining all functions
unsigned maxInlinedInsts = 0;
for (auto pFunc : CallableFuncs)
{
maxInlinedInsts += pFunc->getInstructionCount();
// Use the OCLInlineThreshold for now
if (maxInlinedInsts > IGC_GET_FLAG_VALUE(OCLInlineThreshold))
{
return false;
}
}
SmallVector<std::pair<Value*, BasicBlock*>, 8> callToBBPair;
SmallVector<Value*, 8> callArgs(CI.arg_begin(), CI.arg_end());
IGCIRBuilder<> IRB(pModule->getContext());
IRB.SetInsertPoint(&CI);
Value* calledAddr = IRB.CreatePtrToInt(IGCLLVM::getCalledValue(CI), IRB.getInt64Ty());
BasicBlock* beginBlock = CI.getParent();
BasicBlock* endBlock = beginBlock->splitBasicBlock(&CI, "endIndirectCallBB");
// Remove the original terminator created during the splitBasicBlock. We will replace it with a conditional branch
beginBlock->getTerminator()->eraseFromParent();
std::map<Function*, std::pair<BasicBlock*, BasicBlock*>> funcToBBPairMap;
for (auto pFunc : CallableFuncs)
{
BasicBlock* callBlock = BasicBlock::Create(pModule->getContext(), "funcThen", currFunc, endBlock);
BasicBlock* condBlock = BasicBlock::Create(pModule->getContext(), "funcElse", currFunc, endBlock);
funcToBBPairMap[pFunc] = std::make_pair(callBlock, condBlock);
}
IRB.SetInsertPoint(beginBlock);
for (auto it = CallableFuncs.begin(), ie = CallableFuncs.end(); it != ie; it++)
{
Function* pFunc = *it;
Value* funcAddr = IRB.CreatePtrToInt(pFunc, IRB.getInt64Ty());
Value* cnd = IRB.CreateICmpEQ(calledAddr, funcAddr);
auto brPair = funcToBBPairMap[pFunc];
IRB.CreateCondBr(cnd, brPair.first, brPair.second);
IRB.SetInsertPoint(brPair.first);
CallInst* directCall = IRB.CreateCall(pFunc, callArgs);
callToBBPair.push_back(std::make_pair(directCall, brPair.first));
IRB.CreateBr(endBlock);
IRB.SetInsertPoint(brPair.second);
if (std::distance(it, ie) == 1)
{
// In the final "else" block, if none of the addresses match, do nothing and create undef value
callToBBPair.push_back(std::make_pair(UndefValue::get(CI.getType()), brPair.second));
IRB.CreateBr(endBlock);
}
}
// Return values have to be selected based on which block the function was called
if (callToBBPair.size() > 0 && CI.getType() != IRB.getVoidTy())
{
IRB.SetInsertPoint(&*(endBlock->begin()));
PHINode* phi = IRB.CreatePHI(CI.getType(), callToBBPair.size());
for (auto it : callToBBPair)
{
phi->addIncoming(it.first, it.second);
}
CI.replaceAllUsesWith(phi);
}
return true;
}
}
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