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767 lines
30 KiB
767 lines
30 KiB
//===- CodeExtractor.cpp - Pull code region into a new function -----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the interface to tear out a code region, such as an
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// individual loop or a parallel section, into a new function, replacing it with
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// a call to the new function.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/CodeExtractor.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/RegionInfo.h"
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#include "llvm/Analysis/RegionIterator.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Verifier.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include <algorithm>
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#include <set>
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using namespace llvm;
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#define DEBUG_TYPE "code-extractor"
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// Provide a command-line option to aggregate function arguments into a struct
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// for functions produced by the code extractor. This is useful when converting
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// extracted functions to pthread-based code, as only one argument (void*) can
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// be passed in to pthread_create().
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static cl::opt<bool>
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AggregateArgsOpt("aggregate-extracted-args", cl::Hidden,
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cl::desc("Aggregate arguments to code-extracted functions"));
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/// \brief Test whether a block is valid for extraction.
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static bool isBlockValidForExtraction(const BasicBlock &BB) {
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// Landing pads must be in the function where they were inserted for cleanup.
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if (BB.isEHPad())
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return false;
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// Don't hoist code containing allocas, invokes, or vastarts.
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for (BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
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if (isa<AllocaInst>(I) || isa<InvokeInst>(I))
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return false;
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if (const CallInst *CI = dyn_cast<CallInst>(I))
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if (const Function *F = CI->getCalledFunction())
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if (F->getIntrinsicID() == Intrinsic::vastart)
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return false;
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}
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return true;
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}
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/// \brief Build a set of blocks to extract if the input blocks are viable.
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template <typename IteratorT>
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static SetVector<BasicBlock *> buildExtractionBlockSet(IteratorT BBBegin,
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IteratorT BBEnd) {
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SetVector<BasicBlock *> Result;
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assert(BBBegin != BBEnd);
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// Loop over the blocks, adding them to our set-vector, and aborting with an
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// empty set if we encounter invalid blocks.
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do {
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if (!Result.insert(*BBBegin))
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llvm_unreachable("Repeated basic blocks in extraction input");
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if (!isBlockValidForExtraction(**BBBegin)) {
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Result.clear();
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return Result;
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}
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} while (++BBBegin != BBEnd);
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#ifndef NDEBUG
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for (SetVector<BasicBlock *>::iterator I = std::next(Result.begin()),
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E = Result.end();
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I != E; ++I)
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for (pred_iterator PI = pred_begin(*I), PE = pred_end(*I);
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PI != PE; ++PI)
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assert(Result.count(*PI) &&
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"No blocks in this region may have entries from outside the region"
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" except for the first block!");
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#endif
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return Result;
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}
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/// \brief Helper to call buildExtractionBlockSet with an ArrayRef.
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static SetVector<BasicBlock *>
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buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs) {
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return buildExtractionBlockSet(BBs.begin(), BBs.end());
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}
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/// \brief Helper to call buildExtractionBlockSet with a RegionNode.
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static SetVector<BasicBlock *>
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buildExtractionBlockSet(const RegionNode &RN) {
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if (!RN.isSubRegion())
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// Just a single BasicBlock.
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return buildExtractionBlockSet(RN.getNodeAs<BasicBlock>());
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const Region &R = *RN.getNodeAs<Region>();
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return buildExtractionBlockSet(R.block_begin(), R.block_end());
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}
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CodeExtractor::CodeExtractor(BasicBlock *BB, bool AggregateArgs)
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: DT(nullptr), AggregateArgs(AggregateArgs||AggregateArgsOpt),
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Blocks(buildExtractionBlockSet(BB)), NumExitBlocks(~0U) {}
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CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
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bool AggregateArgs)
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: DT(DT), AggregateArgs(AggregateArgs||AggregateArgsOpt),
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Blocks(buildExtractionBlockSet(BBs)), NumExitBlocks(~0U) {}
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CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs)
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: DT(&DT), AggregateArgs(AggregateArgs||AggregateArgsOpt),
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Blocks(buildExtractionBlockSet(L.getBlocks())), NumExitBlocks(~0U) {}
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CodeExtractor::CodeExtractor(DominatorTree &DT, const RegionNode &RN,
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bool AggregateArgs)
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: DT(&DT), AggregateArgs(AggregateArgs||AggregateArgsOpt),
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Blocks(buildExtractionBlockSet(RN)), NumExitBlocks(~0U) {}
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/// definedInRegion - Return true if the specified value is defined in the
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/// extracted region.
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static bool definedInRegion(const SetVector<BasicBlock *> &Blocks, Value *V) {
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if (Instruction *I = dyn_cast<Instruction>(V))
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if (Blocks.count(I->getParent()))
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return true;
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return false;
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}
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/// definedInCaller - Return true if the specified value is defined in the
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/// function being code extracted, but not in the region being extracted.
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/// These values must be passed in as live-ins to the function.
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static bool definedInCaller(const SetVector<BasicBlock *> &Blocks, Value *V) {
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if (isa<Argument>(V)) return true;
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if (Instruction *I = dyn_cast<Instruction>(V))
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if (!Blocks.count(I->getParent()))
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return true;
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return false;
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}
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void CodeExtractor::findInputsOutputs(ValueSet &Inputs,
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ValueSet &Outputs) const {
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for (BasicBlock *BB : Blocks) {
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// If a used value is defined outside the region, it's an input. If an
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// instruction is used outside the region, it's an output.
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for (Instruction &II : *BB) {
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for (User::op_iterator OI = II.op_begin(), OE = II.op_end(); OI != OE;
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++OI)
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if (definedInCaller(Blocks, *OI))
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Inputs.insert(*OI);
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for (User *U : II.users())
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if (!definedInRegion(Blocks, U)) {
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Outputs.insert(&II);
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break;
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}
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}
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}
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}
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/// severSplitPHINodes - If a PHI node has multiple inputs from outside of the
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/// region, we need to split the entry block of the region so that the PHI node
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/// is easier to deal with.
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void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) {
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unsigned NumPredsFromRegion = 0;
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unsigned NumPredsOutsideRegion = 0;
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if (Header != &Header->getParent()->getEntryBlock()) {
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PHINode *PN = dyn_cast<PHINode>(Header->begin());
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if (!PN) return; // No PHI nodes.
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// If the header node contains any PHI nodes, check to see if there is more
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// than one entry from outside the region. If so, we need to sever the
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// header block into two.
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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if (Blocks.count(PN->getIncomingBlock(i)))
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++NumPredsFromRegion;
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else
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++NumPredsOutsideRegion;
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// If there is one (or fewer) predecessor from outside the region, we don't
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// need to do anything special.
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if (NumPredsOutsideRegion <= 1) return;
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}
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// Otherwise, we need to split the header block into two pieces: one
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// containing PHI nodes merging values from outside of the region, and a
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// second that contains all of the code for the block and merges back any
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// incoming values from inside of the region.
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BasicBlock::iterator AfterPHIs = Header->getFirstNonPHI()->getIterator();
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BasicBlock *NewBB = Header->splitBasicBlock(AfterPHIs,
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Header->getName()+".ce");
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// We only want to code extract the second block now, and it becomes the new
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// header of the region.
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BasicBlock *OldPred = Header;
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Blocks.remove(OldPred);
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Blocks.insert(NewBB);
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Header = NewBB;
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// Okay, update dominator sets. The blocks that dominate the new one are the
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// blocks that dominate TIBB plus the new block itself.
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if (DT)
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DT->splitBlock(NewBB);
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// Okay, now we need to adjust the PHI nodes and any branches from within the
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// region to go to the new header block instead of the old header block.
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if (NumPredsFromRegion) {
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PHINode *PN = cast<PHINode>(OldPred->begin());
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// Loop over all of the predecessors of OldPred that are in the region,
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// changing them to branch to NewBB instead.
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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if (Blocks.count(PN->getIncomingBlock(i))) {
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TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator();
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TI->replaceUsesOfWith(OldPred, NewBB);
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}
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// Okay, everything within the region is now branching to the right block, we
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// just have to update the PHI nodes now, inserting PHI nodes into NewBB.
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for (AfterPHIs = OldPred->begin(); isa<PHINode>(AfterPHIs); ++AfterPHIs) {
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PHINode *PN = cast<PHINode>(AfterPHIs);
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// Create a new PHI node in the new region, which has an incoming value
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// from OldPred of PN.
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PHINode *NewPN = PHINode::Create(PN->getType(), 1 + NumPredsFromRegion,
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PN->getName() + ".ce", &NewBB->front());
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NewPN->addIncoming(PN, OldPred);
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// Loop over all of the incoming value in PN, moving them to NewPN if they
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// are from the extracted region.
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for (unsigned i = 0; i != PN->getNumIncomingValues(); ++i) {
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if (Blocks.count(PN->getIncomingBlock(i))) {
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NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i));
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PN->removeIncomingValue(i);
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--i;
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}
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}
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}
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}
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}
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void CodeExtractor::splitReturnBlocks() {
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for (BasicBlock *Block : Blocks)
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if (ReturnInst *RI = dyn_cast<ReturnInst>(Block->getTerminator())) {
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BasicBlock *New =
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Block->splitBasicBlock(RI->getIterator(), Block->getName() + ".ret");
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if (DT) {
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// Old dominates New. New node dominates all other nodes dominated
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// by Old.
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DomTreeNode *OldNode = DT->getNode(Block);
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SmallVector<DomTreeNode *, 8> Children(OldNode->begin(),
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OldNode->end());
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DomTreeNode *NewNode = DT->addNewBlock(New, Block);
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for (DomTreeNode *I : Children)
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DT->changeImmediateDominator(I, NewNode);
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}
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}
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}
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/// constructFunction - make a function based on inputs and outputs, as follows:
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/// f(in0, ..., inN, out0, ..., outN)
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///
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Function *CodeExtractor::constructFunction(const ValueSet &inputs,
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const ValueSet &outputs,
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BasicBlock *header,
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BasicBlock *newRootNode,
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BasicBlock *newHeader,
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Function *oldFunction,
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Module *M) {
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DEBUG(dbgs() << "inputs: " << inputs.size() << "\n");
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DEBUG(dbgs() << "outputs: " << outputs.size() << "\n");
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// This function returns unsigned, outputs will go back by reference.
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switch (NumExitBlocks) {
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case 0:
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case 1: RetTy = Type::getVoidTy(header->getContext()); break;
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case 2: RetTy = Type::getInt1Ty(header->getContext()); break;
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default: RetTy = Type::getInt16Ty(header->getContext()); break;
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}
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std::vector<Type*> paramTy;
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// Add the types of the input values to the function's argument list
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for (Value *value : inputs) {
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DEBUG(dbgs() << "value used in func: " << *value << "\n");
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paramTy.push_back(value->getType());
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}
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// Add the types of the output values to the function's argument list.
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for (Value *output : outputs) {
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DEBUG(dbgs() << "instr used in func: " << *output << "\n");
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if (AggregateArgs)
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paramTy.push_back(output->getType());
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else
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paramTy.push_back(PointerType::getUnqual(output->getType()));
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}
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DEBUG({
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dbgs() << "Function type: " << *RetTy << " f(";
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for (Type *i : paramTy)
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dbgs() << *i << ", ";
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dbgs() << ")\n";
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});
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StructType *StructTy;
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if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
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StructTy = StructType::get(M->getContext(), paramTy);
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paramTy.clear();
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paramTy.push_back(PointerType::getUnqual(StructTy));
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}
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FunctionType *funcType =
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FunctionType::get(RetTy, paramTy, false);
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// Create the new function
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Function *newFunction = Function::Create(funcType,
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GlobalValue::InternalLinkage,
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oldFunction->getName() + "_" +
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header->getName(), M);
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// If the old function is no-throw, so is the new one.
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if (oldFunction->doesNotThrow())
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newFunction->setDoesNotThrow();
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newFunction->getBasicBlockList().push_back(newRootNode);
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// Create an iterator to name all of the arguments we inserted.
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Function::arg_iterator AI = newFunction->arg_begin();
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// Rewrite all users of the inputs in the extracted region to use the
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// arguments (or appropriate addressing into struct) instead.
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for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
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Value *RewriteVal;
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if (AggregateArgs) {
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Value *Idx[2];
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Idx[0] = Constant::getNullValue(Type::getInt32Ty(header->getContext()));
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Idx[1] = ConstantInt::get(Type::getInt32Ty(header->getContext()), i);
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TerminatorInst *TI = newFunction->begin()->getTerminator();
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GetElementPtrInst *GEP = GetElementPtrInst::Create(
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StructTy, &*AI, Idx, "gep_" + inputs[i]->getName(), TI);
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RewriteVal = new LoadInst(GEP, "loadgep_" + inputs[i]->getName(), TI);
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} else
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RewriteVal = &*AI++;
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std::vector<User*> Users(inputs[i]->user_begin(), inputs[i]->user_end());
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for (User *use : Users)
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if (Instruction *inst = dyn_cast<Instruction>(use))
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if (Blocks.count(inst->getParent()))
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inst->replaceUsesOfWith(inputs[i], RewriteVal);
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}
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// Set names for input and output arguments.
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if (!AggregateArgs) {
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AI = newFunction->arg_begin();
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for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI)
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AI->setName(inputs[i]->getName());
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for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI)
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AI->setName(outputs[i]->getName()+".out");
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}
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// Rewrite branches to basic blocks outside of the loop to new dummy blocks
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// within the new function. This must be done before we lose track of which
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// blocks were originally in the code region.
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std::vector<User*> Users(header->user_begin(), header->user_end());
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for (unsigned i = 0, e = Users.size(); i != e; ++i)
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// The BasicBlock which contains the branch is not in the region
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// modify the branch target to a new block
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if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i]))
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if (!Blocks.count(TI->getParent()) &&
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TI->getParent()->getParent() == oldFunction)
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TI->replaceUsesOfWith(header, newHeader);
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return newFunction;
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}
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/// FindPhiPredForUseInBlock - Given a value and a basic block, find a PHI
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/// that uses the value within the basic block, and return the predecessor
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/// block associated with that use, or return 0 if none is found.
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static BasicBlock* FindPhiPredForUseInBlock(Value* Used, BasicBlock* BB) {
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for (Use &U : Used->uses()) {
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PHINode *P = dyn_cast<PHINode>(U.getUser());
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if (P && P->getParent() == BB)
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return P->getIncomingBlock(U);
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}
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return nullptr;
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}
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/// emitCallAndSwitchStatement - This method sets up the caller side by adding
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/// the call instruction, splitting any PHI nodes in the header block as
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/// necessary.
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void CodeExtractor::
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emitCallAndSwitchStatement(Function *newFunction, BasicBlock *codeReplacer,
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ValueSet &inputs, ValueSet &outputs) {
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// Emit a call to the new function, passing in: *pointer to struct (if
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// aggregating parameters), or plan inputs and allocated memory for outputs
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std::vector<Value*> params, StructValues, ReloadOutputs, Reloads;
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LLVMContext &Context = newFunction->getContext();
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// Add inputs as params, or to be filled into the struct
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for (Value *input : inputs)
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if (AggregateArgs)
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StructValues.push_back(input);
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else
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params.push_back(input);
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// Create allocas for the outputs
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for (Value *output : outputs) {
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if (AggregateArgs) {
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StructValues.push_back(output);
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} else {
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AllocaInst *alloca =
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new AllocaInst(output->getType(), nullptr, output->getName() + ".loc",
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&codeReplacer->getParent()->front().front());
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ReloadOutputs.push_back(alloca);
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params.push_back(alloca);
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}
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}
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StructType *StructArgTy = nullptr;
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AllocaInst *Struct = nullptr;
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if (AggregateArgs && (inputs.size() + outputs.size() > 0)) {
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std::vector<Type*> ArgTypes;
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for (ValueSet::iterator v = StructValues.begin(),
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ve = StructValues.end(); v != ve; ++v)
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ArgTypes.push_back((*v)->getType());
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// Allocate a struct at the beginning of this function
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StructArgTy = StructType::get(newFunction->getContext(), ArgTypes);
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Struct = new AllocaInst(StructArgTy, nullptr, "structArg",
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&codeReplacer->getParent()->front().front());
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params.push_back(Struct);
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for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
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Value *Idx[2];
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Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context));
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Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), i);
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GetElementPtrInst *GEP = GetElementPtrInst::Create(
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StructArgTy, Struct, Idx, "gep_" + StructValues[i]->getName());
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codeReplacer->getInstList().push_back(GEP);
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StoreInst *SI = new StoreInst(StructValues[i], GEP);
|
|
codeReplacer->getInstList().push_back(SI);
|
|
}
|
|
}
|
|
|
|
// Emit the call to the function
|
|
CallInst *call = CallInst::Create(newFunction, params,
|
|
NumExitBlocks > 1 ? "targetBlock" : "");
|
|
codeReplacer->getInstList().push_back(call);
|
|
|
|
Function::arg_iterator OutputArgBegin = newFunction->arg_begin();
|
|
unsigned FirstOut = inputs.size();
|
|
if (!AggregateArgs)
|
|
std::advance(OutputArgBegin, inputs.size());
|
|
|
|
// Reload the outputs passed in by reference
|
|
for (unsigned i = 0, e = outputs.size(); i != e; ++i) {
|
|
Value *Output = nullptr;
|
|
if (AggregateArgs) {
|
|
Value *Idx[2];
|
|
Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context));
|
|
Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), FirstOut + i);
|
|
GetElementPtrInst *GEP = GetElementPtrInst::Create(
|
|
StructArgTy, Struct, Idx, "gep_reload_" + outputs[i]->getName());
|
|
codeReplacer->getInstList().push_back(GEP);
|
|
Output = GEP;
|
|
} else {
|
|
Output = ReloadOutputs[i];
|
|
}
|
|
LoadInst *load = new LoadInst(Output, outputs[i]->getName()+".reload");
|
|
Reloads.push_back(load);
|
|
codeReplacer->getInstList().push_back(load);
|
|
std::vector<User*> Users(outputs[i]->user_begin(), outputs[i]->user_end());
|
|
for (unsigned u = 0, e = Users.size(); u != e; ++u) {
|
|
Instruction *inst = cast<Instruction>(Users[u]);
|
|
if (!Blocks.count(inst->getParent()))
|
|
inst->replaceUsesOfWith(outputs[i], load);
|
|
}
|
|
}
|
|
|
|
// Now we can emit a switch statement using the call as a value.
|
|
SwitchInst *TheSwitch =
|
|
SwitchInst::Create(Constant::getNullValue(Type::getInt16Ty(Context)),
|
|
codeReplacer, 0, codeReplacer);
|
|
|
|
// Since there may be multiple exits from the original region, make the new
|
|
// function return an unsigned, switch on that number. This loop iterates
|
|
// over all of the blocks in the extracted region, updating any terminator
|
|
// instructions in the to-be-extracted region that branch to blocks that are
|
|
// not in the region to be extracted.
|
|
std::map<BasicBlock*, BasicBlock*> ExitBlockMap;
|
|
|
|
unsigned switchVal = 0;
|
|
for (BasicBlock *Block : Blocks) {
|
|
TerminatorInst *TI = Block->getTerminator();
|
|
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
|
|
if (!Blocks.count(TI->getSuccessor(i))) {
|
|
BasicBlock *OldTarget = TI->getSuccessor(i);
|
|
// add a new basic block which returns the appropriate value
|
|
BasicBlock *&NewTarget = ExitBlockMap[OldTarget];
|
|
if (!NewTarget) {
|
|
// If we don't already have an exit stub for this non-extracted
|
|
// destination, create one now!
|
|
NewTarget = BasicBlock::Create(Context,
|
|
OldTarget->getName() + ".exitStub",
|
|
newFunction);
|
|
unsigned SuccNum = switchVal++;
|
|
|
|
Value *brVal = nullptr;
|
|
switch (NumExitBlocks) {
|
|
case 0:
|
|
case 1: break; // No value needed.
|
|
case 2: // Conditional branch, return a bool
|
|
brVal = ConstantInt::get(Type::getInt1Ty(Context), !SuccNum);
|
|
break;
|
|
default:
|
|
brVal = ConstantInt::get(Type::getInt16Ty(Context), SuccNum);
|
|
break;
|
|
}
|
|
|
|
ReturnInst *NTRet = ReturnInst::Create(Context, brVal, NewTarget);
|
|
|
|
// Update the switch instruction.
|
|
TheSwitch->addCase(ConstantInt::get(Type::getInt16Ty(Context),
|
|
SuccNum),
|
|
OldTarget);
|
|
|
|
// Restore values just before we exit
|
|
Function::arg_iterator OAI = OutputArgBegin;
|
|
for (unsigned out = 0, e = outputs.size(); out != e; ++out) {
|
|
// For an invoke, the normal destination is the only one that is
|
|
// dominated by the result of the invocation
|
|
BasicBlock *DefBlock = cast<Instruction>(outputs[out])->getParent();
|
|
|
|
bool DominatesDef = true;
|
|
|
|
BasicBlock *NormalDest = nullptr;
|
|
if (auto *Invoke = dyn_cast<InvokeInst>(outputs[out]))
|
|
NormalDest = Invoke->getNormalDest();
|
|
|
|
if (NormalDest) {
|
|
DefBlock = NormalDest;
|
|
|
|
// Make sure we are looking at the original successor block, not
|
|
// at a newly inserted exit block, which won't be in the dominator
|
|
// info.
|
|
for (const auto &I : ExitBlockMap)
|
|
if (DefBlock == I.second) {
|
|
DefBlock = I.first;
|
|
break;
|
|
}
|
|
|
|
// In the extract block case, if the block we are extracting ends
|
|
// with an invoke instruction, make sure that we don't emit a
|
|
// store of the invoke value for the unwind block.
|
|
if (!DT && DefBlock != OldTarget)
|
|
DominatesDef = false;
|
|
}
|
|
|
|
if (DT) {
|
|
DominatesDef = DT->dominates(DefBlock, OldTarget);
|
|
|
|
// If the output value is used by a phi in the target block,
|
|
// then we need to test for dominance of the phi's predecessor
|
|
// instead. Unfortunately, this a little complicated since we
|
|
// have already rewritten uses of the value to uses of the reload.
|
|
BasicBlock* pred = FindPhiPredForUseInBlock(Reloads[out],
|
|
OldTarget);
|
|
if (pred && DT && DT->dominates(DefBlock, pred))
|
|
DominatesDef = true;
|
|
}
|
|
|
|
if (DominatesDef) {
|
|
if (AggregateArgs) {
|
|
Value *Idx[2];
|
|
Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context));
|
|
Idx[1] = ConstantInt::get(Type::getInt32Ty(Context),
|
|
FirstOut+out);
|
|
GetElementPtrInst *GEP = GetElementPtrInst::Create(
|
|
StructArgTy, &*OAI, Idx, "gep_" + outputs[out]->getName(),
|
|
NTRet);
|
|
new StoreInst(outputs[out], GEP, NTRet);
|
|
} else {
|
|
new StoreInst(outputs[out], &*OAI, NTRet);
|
|
}
|
|
}
|
|
// Advance output iterator even if we don't emit a store
|
|
if (!AggregateArgs) ++OAI;
|
|
}
|
|
}
|
|
|
|
// rewrite the original branch instruction with this new target
|
|
TI->setSuccessor(i, NewTarget);
|
|
}
|
|
}
|
|
|
|
// Now that we've done the deed, simplify the switch instruction.
|
|
Type *OldFnRetTy = TheSwitch->getParent()->getParent()->getReturnType();
|
|
switch (NumExitBlocks) {
|
|
case 0:
|
|
// There are no successors (the block containing the switch itself), which
|
|
// means that previously this was the last part of the function, and hence
|
|
// this should be rewritten as a `ret'
|
|
|
|
// Check if the function should return a value
|
|
if (OldFnRetTy->isVoidTy()) {
|
|
ReturnInst::Create(Context, nullptr, TheSwitch); // Return void
|
|
} else if (OldFnRetTy == TheSwitch->getCondition()->getType()) {
|
|
// return what we have
|
|
ReturnInst::Create(Context, TheSwitch->getCondition(), TheSwitch);
|
|
} else {
|
|
// Otherwise we must have code extracted an unwind or something, just
|
|
// return whatever we want.
|
|
ReturnInst::Create(Context,
|
|
Constant::getNullValue(OldFnRetTy), TheSwitch);
|
|
}
|
|
|
|
TheSwitch->eraseFromParent();
|
|
break;
|
|
case 1:
|
|
// Only a single destination, change the switch into an unconditional
|
|
// branch.
|
|
BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch);
|
|
TheSwitch->eraseFromParent();
|
|
break;
|
|
case 2:
|
|
BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch->getSuccessor(2),
|
|
call, TheSwitch);
|
|
TheSwitch->eraseFromParent();
|
|
break;
|
|
default:
|
|
// Otherwise, make the default destination of the switch instruction be one
|
|
// of the other successors.
|
|
TheSwitch->setCondition(call);
|
|
TheSwitch->setDefaultDest(TheSwitch->getSuccessor(NumExitBlocks));
|
|
// Remove redundant case
|
|
TheSwitch->removeCase(SwitchInst::CaseIt(TheSwitch, NumExitBlocks-1));
|
|
break;
|
|
}
|
|
}
|
|
|
|
void CodeExtractor::moveCodeToFunction(Function *newFunction) {
|
|
Function *oldFunc = (*Blocks.begin())->getParent();
|
|
Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
|
|
Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
|
|
|
|
for (BasicBlock *Block : Blocks) {
|
|
// Delete the basic block from the old function, and the list of blocks
|
|
oldBlocks.remove(Block);
|
|
|
|
// Insert this basic block into the new function
|
|
newBlocks.push_back(Block);
|
|
}
|
|
}
|
|
|
|
Function *CodeExtractor::extractCodeRegion() {
|
|
if (!isEligible())
|
|
return nullptr;
|
|
|
|
ValueSet inputs, outputs;
|
|
|
|
// Assumption: this is a single-entry code region, and the header is the first
|
|
// block in the region.
|
|
BasicBlock *header = *Blocks.begin();
|
|
|
|
// If we have to split PHI nodes or the entry block, do so now.
|
|
severSplitPHINodes(header);
|
|
|
|
// If we have any return instructions in the region, split those blocks so
|
|
// that the return is not in the region.
|
|
splitReturnBlocks();
|
|
|
|
Function *oldFunction = header->getParent();
|
|
|
|
// This takes place of the original loop
|
|
BasicBlock *codeReplacer = BasicBlock::Create(header->getContext(),
|
|
"codeRepl", oldFunction,
|
|
header);
|
|
|
|
// The new function needs a root node because other nodes can branch to the
|
|
// head of the region, but the entry node of a function cannot have preds.
|
|
BasicBlock *newFuncRoot = BasicBlock::Create(header->getContext(),
|
|
"newFuncRoot");
|
|
newFuncRoot->getInstList().push_back(BranchInst::Create(header));
|
|
|
|
// Find inputs to, outputs from the code region.
|
|
findInputsOutputs(inputs, outputs);
|
|
|
|
SmallPtrSet<BasicBlock *, 1> ExitBlocks;
|
|
for (BasicBlock *Block : Blocks)
|
|
for (succ_iterator SI = succ_begin(Block), SE = succ_end(Block); SI != SE;
|
|
++SI)
|
|
if (!Blocks.count(*SI))
|
|
ExitBlocks.insert(*SI);
|
|
NumExitBlocks = ExitBlocks.size();
|
|
|
|
// Construct new function based on inputs/outputs & add allocas for all defs.
|
|
Function *newFunction = constructFunction(inputs, outputs, header,
|
|
newFuncRoot,
|
|
codeReplacer, oldFunction,
|
|
oldFunction->getParent());
|
|
|
|
emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
|
|
|
|
moveCodeToFunction(newFunction);
|
|
|
|
// Loop over all of the PHI nodes in the header block, and change any
|
|
// references to the old incoming edge to be the new incoming edge.
|
|
for (BasicBlock::iterator I = header->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PN = cast<PHINode>(I);
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
if (!Blocks.count(PN->getIncomingBlock(i)))
|
|
PN->setIncomingBlock(i, newFuncRoot);
|
|
}
|
|
|
|
// Look at all successors of the codeReplacer block. If any of these blocks
|
|
// had PHI nodes in them, we need to update the "from" block to be the code
|
|
// replacer, not the original block in the extracted region.
|
|
std::vector<BasicBlock*> Succs(succ_begin(codeReplacer),
|
|
succ_end(codeReplacer));
|
|
for (unsigned i = 0, e = Succs.size(); i != e; ++i)
|
|
for (BasicBlock::iterator I = Succs[i]->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PN = cast<PHINode>(I);
|
|
std::set<BasicBlock*> ProcessedPreds;
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
if (Blocks.count(PN->getIncomingBlock(i))) {
|
|
if (ProcessedPreds.insert(PN->getIncomingBlock(i)).second)
|
|
PN->setIncomingBlock(i, codeReplacer);
|
|
else {
|
|
// There were multiple entries in the PHI for this block, now there
|
|
// is only one, so remove the duplicated entries.
|
|
PN->removeIncomingValue(i, false);
|
|
--i; --e;
|
|
}
|
|
}
|
|
}
|
|
|
|
//cerr << "NEW FUNCTION: " << *newFunction;
|
|
// verifyFunction(*newFunction);
|
|
|
|
// cerr << "OLD FUNCTION: " << *oldFunction;
|
|
// verifyFunction(*oldFunction);
|
|
|
|
DEBUG(if (verifyFunction(*newFunction))
|
|
report_fatal_error("verifyFunction failed!"));
|
|
return newFunction;
|
|
}
|