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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
88 lines
3.7 KiB
C++
88 lines
3.7 KiB
C++
//===- OrderedBasicBlock.cpp --------------------------------- -*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the OrderedBasicBlock class. OrderedBasicBlock
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// maintains an interface where clients can query if one instruction comes
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// before another in a BasicBlock. Since BasicBlock currently lacks a reliable
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// way to query relative position between instructions one can use
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// OrderedBasicBlock to do such queries. OrderedBasicBlock is lazily built on a
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// source BasicBlock and maintains an internal Instruction -> Position map. A
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// OrderedBasicBlock instance should be discarded whenever the source
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// BasicBlock changes.
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//
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// It's currently used by the CaptureTracker in order to find relative
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// positions of a pair of instructions inside a BasicBlock.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/OrderedBasicBlock.h"
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#include "llvm/IR/Instruction.h"
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using namespace llvm;
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OrderedBasicBlock::OrderedBasicBlock(const BasicBlock *BasicB)
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: NextInstPos(0), BB(BasicB) {
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LastInstFound = BB->end();
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}
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/// Given no cached results, find if \p A comes before \p B in \p BB.
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/// Cache and number out instruction while walking \p BB.
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bool OrderedBasicBlock::comesBefore(const Instruction *A,
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const Instruction *B) {
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const Instruction *Inst = nullptr;
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assert(!(LastInstFound == BB->end() && NextInstPos != 0) &&
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"Instruction supposed to be in NumberedInsts");
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assert(A->getParent() == BB && "Instruction supposed to be in the block!");
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assert(B->getParent() == BB && "Instruction supposed to be in the block!");
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// Start the search with the instruction found in the last lookup round.
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auto II = BB->begin();
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auto IE = BB->end();
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if (LastInstFound != IE)
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II = std::next(LastInstFound);
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// Number all instructions up to the point where we find 'A' or 'B'.
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for (; II != IE; ++II) {
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Inst = cast<Instruction>(II);
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NumberedInsts[Inst] = NextInstPos++;
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if (Inst == A || Inst == B)
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break;
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}
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assert(II != IE && "Instruction not found?");
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assert((Inst == A || Inst == B) && "Should find A or B");
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LastInstFound = II;
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return Inst != B;
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}
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/// Find out whether \p A dominates \p B, meaning whether \p A
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/// comes before \p B in \p BB. This is a simplification that considers
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/// cached instruction positions and ignores other basic blocks, being
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/// only relevant to compare relative instructions positions inside \p BB.
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bool OrderedBasicBlock::dominates(const Instruction *A, const Instruction *B) {
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assert(A->getParent() == B->getParent() &&
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"Instructions must be in the same basic block!");
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assert(A->getParent() == BB && "Instructions must be in the tracked block!");
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// First we lookup the instructions. If they don't exist, lookup will give us
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// back ::end(). If they both exist, we compare the numbers. Otherwise, if NA
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// exists and NB doesn't, it means NA must come before NB because we would
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// have numbered NB as well if it didn't. The same is true for NB. If it
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// exists, but NA does not, NA must come after it. If neither exist, we need
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// to number the block and cache the results (by calling comesBefore).
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auto NAI = NumberedInsts.find(A);
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auto NBI = NumberedInsts.find(B);
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if (NAI != NumberedInsts.end() && NBI != NumberedInsts.end())
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return NAI->second < NBI->second;
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if (NAI != NumberedInsts.end())
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return true;
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if (NBI != NumberedInsts.end())
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return false;
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return comesBefore(A, B);
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}
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