forked from OSchip/llvm-project
[LoopDist/LoopVer] Move LoopVersioning to a new module, NFC
Summary: The class will obviously need improvement down the road. For one, there is no reason that addPHINodes would have to be exposed like that. I will make this and other improvements in follow-up patches. The main goal is to be able to share this functionality. The LoopLoadElimination pass I am working on needs it too. Later we can move other clients as well (LV and Ashutosh's LICMVer). Reviewers: hfinkel, ashutosh.nema Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D10577 llvm-svn: 241932
This commit is contained in:
Adam Nemet
parent
1a689188c4
commit
215746b45a
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//===- LoopVersioning.h - Utility to version a loop -------------*- C++ -*-===//
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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 defines a utility class to perform loop versioning. The versioned
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// loop speculates that otherwise may-aliasing memory accesses don't overlap and
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// emits checks to prove this.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_LOOPVERSIONING_H
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#define LLVM_TRANSFORMS_UTILS_LOOPVERSIONING_H
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#include "llvm/Transforms/Utils/ValueMapper.h"
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namespace llvm {
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class Loop;
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class LoopAccessInfo;
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class LoopInfo;
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/// \brief This class emits a version of the loop where run-time checks ensure
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/// that may-alias pointers can't overlap.
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///
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/// It currently only supports single-exit loops and assumes that the loop
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/// already has a preheader.
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class LoopVersioning {
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public:
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LoopVersioning(const LoopAccessInfo &LAI, Loop *L, LoopInfo *LI,
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DominatorTree *DT,
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const SmallVector<int, 8> *PtrToPartition = nullptr);
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/// \brief Returns true if we need memchecks to disambiguate may-aliasing
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/// accesses.
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bool needsRuntimeChecks() const;
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/// \brief Performs the CFG manipulation part of versioning the loop including
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/// the DominatorTree and LoopInfo updates.
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///
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/// The loop that was used to construct the class will be the "versioned" loop
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/// i.e. the loop that will receive control if all the memchecks pass.
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///
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/// This allows the loop transform pass to operate on the same loop regardless
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/// of whether versioning was necessary or not:
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///
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/// for each loop L:
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/// analyze L
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/// if versioning is necessary version L
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/// transform L
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void versionLoop(Pass *P);
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/// \brief Adds the necessary PHI nodes for the versioned loops based on the
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/// loop-defined values used outside of the loop.
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///
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/// This needs to be called after versionLoop if there are defs in the loop
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/// that are used outside the loop. FIXME: this should be invoked internally
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/// by versionLoop and made private.
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void addPHINodes(const SmallVectorImpl<Instruction *> &DefsUsedOutside);
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/// \brief Returns the versioned loop. Control flows here if pointers in the
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/// loop don't alias (i.e. all memchecks passed). (This loop is actually the
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/// same as the original loop that we got constructed with.)
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Loop *getVersionedLoop() { return VersionedLoop; }
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/// \brief Returns the fall-back loop. Control flows here if pointers in the
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/// loop may alias (i.e. one of the memchecks failed).
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Loop *getNonVersionedLoop() { return NonVersionedLoop; }
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private:
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/// \brief The original loop. This becomes the "versioned" one. I.e.,
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/// control flows here if pointers in the loop don't alias.
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Loop *VersionedLoop;
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/// \brief The fall-back loop. I.e. control flows here if pointers in the
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/// loop may alias (memchecks failed).
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Loop *NonVersionedLoop;
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/// \brief For each memory pointer it contains the partitionId it is used in.
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/// If nullptr, no partitioning is used.
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///
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/// The I-th entry corresponds to I-th entry in LAI.getRuntimePointerCheck().
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/// If the pointer is used in multiple partitions the entry is set to -1.
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const SmallVector<int, 8> *PtrToPartition;
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/// \brief This maps the instructions from VersionedLoop to their counterpart
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/// in NonVersionedLoop.
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ValueToValueMapTy VMap;
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/// \brief Analyses used.
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const LoopAccessInfo &LAI;
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LoopInfo *LI;
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DominatorTree *DT;
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};
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}
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#endif
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@ -34,6 +34,7 @@
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#include "llvm/Support/Debug.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Transforms/Utils/LoopVersioning.h"
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#include <list>
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#define LDIST_NAME "loop-distribute"
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@ -567,121 +568,6 @@ private:
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AccessesType Accesses;
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};
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/// \brief Handles the loop versioning based on memchecks.
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class LoopVersioning {
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public:
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LoopVersioning(const LoopAccessInfo &LAI, Loop *L, LoopInfo *LI,
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DominatorTree *DT,
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const SmallVector<int, 8> *PtrToPartition = nullptr)
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: VersionedLoop(L), NonVersionedLoop(nullptr),
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PtrToPartition(PtrToPartition), LAI(LAI), LI(LI), DT(DT) {}
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/// \brief Returns true if we need memchecks to disambiguate may-aliasing
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/// accesses.
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bool needsRuntimeChecks() const {
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return LAI.getRuntimePointerCheck()->needsAnyChecking(PtrToPartition);
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}
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/// \brief Performs the CFG manipulation part of versioning the loop including
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/// the DominatorTree and LoopInfo updates.
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void versionLoop(Pass *P) {
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Instruction *FirstCheckInst;
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Instruction *MemRuntimeCheck;
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// Add the memcheck in the original preheader (this is empty initially).
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BasicBlock *MemCheckBB = VersionedLoop->getLoopPreheader();
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std::tie(FirstCheckInst, MemRuntimeCheck) =
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LAI.addRuntimeCheck(MemCheckBB->getTerminator(), PtrToPartition);
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assert(MemRuntimeCheck && "called even though needsAnyChecking = false");
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// Rename the block to make the IR more readable.
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MemCheckBB->setName(VersionedLoop->getHeader()->getName() +
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".lver.memcheck");
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// Create empty preheader for the loop (and after cloning for the
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// non-versioned loop).
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BasicBlock *PH =
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SplitBlock(MemCheckBB, MemCheckBB->getTerminator(), DT, LI);
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PH->setName(VersionedLoop->getHeader()->getName() + ".ph");
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// Clone the loop including the preheader.
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//
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// FIXME: This does not currently preserve SimplifyLoop because the exit
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// block is a join between the two loops.
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SmallVector<BasicBlock *, 8> NonVersionedLoopBlocks;
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NonVersionedLoop =
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cloneLoopWithPreheader(PH, MemCheckBB, VersionedLoop, VMap,
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".lver.orig", LI, DT, NonVersionedLoopBlocks);
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remapInstructionsInBlocks(NonVersionedLoopBlocks, VMap);
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// Insert the conditional branch based on the result of the memchecks.
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Instruction *OrigTerm = MemCheckBB->getTerminator();
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BranchInst::Create(NonVersionedLoop->getLoopPreheader(),
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VersionedLoop->getLoopPreheader(), MemRuntimeCheck,
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OrigTerm);
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OrigTerm->eraseFromParent();
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// The loops merge in the original exit block. This is now dominated by the
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// memchecking block.
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DT->changeImmediateDominator(VersionedLoop->getExitBlock(), MemCheckBB);
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}
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/// \brief Adds the necessary PHI nodes for the versioned loops based on the
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/// loop-defined values used outside of the loop.
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void addPHINodes(const SmallVectorImpl<Instruction *> &DefsUsedOutside) {
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BasicBlock *PHIBlock = VersionedLoop->getExitBlock();
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assert(PHIBlock && "No single successor to loop exit block");
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for (auto *Inst : DefsUsedOutside) {
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auto *NonVersionedLoopInst = cast<Instruction>(VMap[Inst]);
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PHINode *PN;
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// First see if we have a single-operand PHI with the value defined by the
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// original loop.
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for (auto I = PHIBlock->begin(); (PN = dyn_cast<PHINode>(I)); ++I) {
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assert(PN->getNumOperands() == 1 &&
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"Exit block should only have on predecessor");
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if (PN->getIncomingValue(0) == Inst)
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break;
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}
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// If not create it.
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if (!PN) {
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PN = PHINode::Create(Inst->getType(), 2, Inst->getName() + ".lver",
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PHIBlock->begin());
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for (auto *User : Inst->users())
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if (!VersionedLoop->contains(cast<Instruction>(User)->getParent()))
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User->replaceUsesOfWith(Inst, PN);
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PN->addIncoming(Inst, VersionedLoop->getExitingBlock());
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}
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// Add the new incoming value from the non-versioned loop.
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PN->addIncoming(NonVersionedLoopInst,
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NonVersionedLoop->getExitingBlock());
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}
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}
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private:
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/// \brief The original loop. This becomes the "versioned" one, i.e. control
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/// goes if the memchecks all pass.
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Loop *VersionedLoop;
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/// \brief The fall-back loop, i.e. if any of the memchecks fail.
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Loop *NonVersionedLoop;
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/// \brief For each memory pointer it contains the partitionId it is used in.
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/// If nullptr, no partitioning is used.
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///
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/// The I-th entry corresponds to I-th entry in LAI.getRuntimePointerCheck().
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/// If the pointer is used in multiple partitions the entry is set to -1.
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const SmallVector<int, 8> *PtrToPartition;
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/// \brief This maps the instructions from VersionedLoop to their counterpart
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/// in NonVersionedLoop.
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ValueToValueMapTy VMap;
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/// \brief Analyses used.
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const LoopAccessInfo &LAI;
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LoopInfo *LI;
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DominatorTree *DT;
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};
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/// \brief Returns the instructions that use values defined in the loop.
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static SmallVector<Instruction *, 8> findDefsUsedOutsideOfLoop(Loop *L) {
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SmallVector<Instruction *, 8> UsedOutside;
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@ -22,6 +22,7 @@ add_llvm_library(LLVMTransformUtils
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LoopUnroll.cpp
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LoopUnrollRuntime.cpp
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LoopUtils.cpp
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LoopVersioning.cpp
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LowerInvoke.cpp
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LowerSwitch.cpp
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Mem2Reg.cpp
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@ -0,0 +1,106 @@
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//===- LoopVersioning.cpp - Utility to version a loop ---------------------===//
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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 defines a utility class to perform loop versioning. The versioned
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// loop speculates that otherwise may-aliasing memory accesses don't overlap and
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// emits checks to prove this.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/LoopAccessAnalysis.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Transforms/Utils/LoopVersioning.h"
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using namespace llvm;
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LoopVersioning::LoopVersioning(const LoopAccessInfo &LAI, Loop *L, LoopInfo *LI,
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DominatorTree *DT,
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const SmallVector<int, 8> *PtrToPartition)
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: VersionedLoop(L), NonVersionedLoop(nullptr),
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PtrToPartition(PtrToPartition), LAI(LAI), LI(LI), DT(DT) {
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assert(L->getExitBlock() && "No single exit block");
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assert(L->getLoopPreheader() && "No preheader");
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}
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bool LoopVersioning::needsRuntimeChecks() const {
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return LAI.getRuntimePointerCheck()->needsAnyChecking(PtrToPartition);
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}
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void LoopVersioning::versionLoop(Pass *P) {
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Instruction *FirstCheckInst;
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Instruction *MemRuntimeCheck;
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// Add the memcheck in the original preheader (this is empty initially).
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BasicBlock *MemCheckBB = VersionedLoop->getLoopPreheader();
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std::tie(FirstCheckInst, MemRuntimeCheck) =
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LAI.addRuntimeCheck(MemCheckBB->getTerminator(), PtrToPartition);
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assert(MemRuntimeCheck && "called even though needsAnyChecking = false");
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// Rename the block to make the IR more readable.
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MemCheckBB->setName(VersionedLoop->getHeader()->getName() + ".lver.memcheck");
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// Create empty preheader for the loop (and after cloning for the
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// non-versioned loop).
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BasicBlock *PH = SplitBlock(MemCheckBB, MemCheckBB->getTerminator(), DT, LI);
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PH->setName(VersionedLoop->getHeader()->getName() + ".ph");
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// Clone the loop including the preheader.
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//
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// FIXME: This does not currently preserve SimplifyLoop because the exit
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// block is a join between the two loops.
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SmallVector<BasicBlock *, 8> NonVersionedLoopBlocks;
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NonVersionedLoop =
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cloneLoopWithPreheader(PH, MemCheckBB, VersionedLoop, VMap, ".lver.orig",
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LI, DT, NonVersionedLoopBlocks);
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remapInstructionsInBlocks(NonVersionedLoopBlocks, VMap);
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// Insert the conditional branch based on the result of the memchecks.
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Instruction *OrigTerm = MemCheckBB->getTerminator();
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BranchInst::Create(NonVersionedLoop->getLoopPreheader(),
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VersionedLoop->getLoopPreheader(), MemRuntimeCheck,
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OrigTerm);
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OrigTerm->eraseFromParent();
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// The loops merge in the original exit block. This is now dominated by the
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// memchecking block.
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DT->changeImmediateDominator(VersionedLoop->getExitBlock(), MemCheckBB);
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}
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void LoopVersioning::addPHINodes(
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const SmallVectorImpl<Instruction *> &DefsUsedOutside) {
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BasicBlock *PHIBlock = VersionedLoop->getExitBlock();
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assert(PHIBlock && "No single successor to loop exit block");
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for (auto *Inst : DefsUsedOutside) {
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auto *NonVersionedLoopInst = cast<Instruction>(VMap[Inst]);
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PHINode *PN;
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// First see if we have a single-operand PHI with the value defined by the
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// original loop.
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for (auto I = PHIBlock->begin(); (PN = dyn_cast<PHINode>(I)); ++I) {
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assert(PN->getNumOperands() == 1 &&
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"Exit block should only have on predecessor");
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if (PN->getIncomingValue(0) == Inst)
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break;
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}
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// If not create it.
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if (!PN) {
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PN = PHINode::Create(Inst->getType(), 2, Inst->getName() + ".lver",
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PHIBlock->begin());
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for (auto *User : Inst->users())
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if (!VersionedLoop->contains(cast<Instruction>(User)->getParent()))
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User->replaceUsesOfWith(Inst, PN);
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PN->addIncoming(Inst, VersionedLoop->getExitingBlock());
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}
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// Add the new incoming value from the non-versioned loop.
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PN->addIncoming(NonVersionedLoopInst, NonVersionedLoop->getExitingBlock());
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}
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}
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