mirror of
https://github.com/intel/intel-graphics-compiler.git
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92 lines
3.2 KiB
C++
92 lines
3.2 KiB
C++
/*========================== begin_copyright_notice ============================
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Copyright (C) 2022-2023 Intel Corporation
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SPDX-License-Identifier: MIT
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============================= end_copyright_notice ===========================*/
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//===----------------------------------------------------------------------===//
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//
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// The purpose of this pass is to add a limit for each loop,
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// so no infinite loops occur.
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//===----------------------------------------------------------------------===//
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#include "CapLoopIterationsPass.h"
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#include "IGCIRBuilder.h"
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#include "Compiler/IGCPassSupport.h"
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#include "common/LLVMWarningsPush.hpp"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "common/LLVMWarningsPop.hpp"
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using namespace llvm;
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using namespace IGC;
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// Register pass to igc-opt
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#define PASS_FLAG "cap-loop-iterations-pass"
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#define PASS_DESCRIPTION "Limit the number of iterations in each loop to UINT_MAX. Prevents inifinite loops"
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#define PASS_CFG_ONLY false
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#define PASS_ANALYSIS false
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IGC_INITIALIZE_PASS_BEGIN(CapLoopIterations, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
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IGC_INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
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IGC_INITIALIZE_PASS_END(CapLoopIterations, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
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char CapLoopIterations::ID = 0;
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CapLoopIterations::CapLoopIterations() : FunctionPass(ID), m_iterationLimit(UINT_MAX) {
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initializeCapLoopIterationsPass(*PassRegistry::getPassRegistry());
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}
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CapLoopIterations::CapLoopIterations(uint32_t iterationLimit) : FunctionPass(ID), m_iterationLimit(iterationLimit) {
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initializeCapLoopIterationsPass(*PassRegistry::getPassRegistry());
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}
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void CapLoopIterations::getAnalysisUsage(llvm::AnalysisUsage &AU) const { AU.addRequired<LoopInfoWrapperPass>(); }
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bool CapLoopIterations::runOnFunction(Function &F) {
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auto changed = false;
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auto &loopInfo = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
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auto IRB = IRBuilder(F.getContext());
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for (auto loop : loopInfo.getLoopsInPreorder()) {
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if (!loop->isLoopSimplifyForm()) // preheader is required
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continue;
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IRB.SetInsertPoint(loop->getHeader()->getFirstNonPHI());
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auto counterphi = IRB.CreatePHI(IRB.getInt32Ty(), 2, "counterphi");
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counterphi->addIncoming(IRB.getInt32(0), loop->getLoopPreheader());
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auto counter = IRB.CreateAdd(counterphi, IRB.getInt32(1), "counter");
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counterphi->addIncoming(counter, loop->getLoopLatch());
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auto forceexit = IRB.CreateICmpEQ(counter, IRB.getInt32(m_iterationLimit), "forceloopexit");
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llvm::SmallVector<std::pair<BasicBlock *, BasicBlock *>, 4> exitedges;
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loop->getExitEdges(exitedges);
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for (const auto &[exitingbb, exitbb] : exitedges) {
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if (auto br = dyn_cast<BranchInst>(exitingbb->getTerminator())) {
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if (!br->isConditional())
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continue;
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IRB.SetInsertPoint(br);
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if (br->getSuccessor(0) == exitbb) // br i1 %cond, %exit, %notexit
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{
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br->setCondition(IRB.CreateOr(forceexit, br->getCondition()));
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} else // br i1 %cond, %notexit, %exit
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{
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br->setCondition(IRB.CreateAnd(IRB.CreateNot(forceexit), br->getCondition()));
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}
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}
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}
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changed = true;
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}
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return changed;
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}
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