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cleaner to derive from the generic base. Thise removes a ton of boiler plate code and somewhat strange and pointless indirections. It also remove a bunch of the previously needed friend declarations. To fully remove these, I also lifted the verify logic into the generic LoopInfoBase, which seems good anyways -- it is generic and useful logic even for the machine side. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226385 91177308-0d34-0410-b5e6-96231b3b80d8
570 lines
21 KiB
C++
570 lines
21 KiB
C++
//===- llvm/Analysis/LoopInfoImpl.h - Natural Loop Calculator ---*- 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 is the generic implementation of LoopInfo used for both Loops and
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// MachineLoops.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_LOOPINFOIMPL_H
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#define LLVM_ANALYSIS_LOOPINFOIMPL_H
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/Dominators.h"
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namespace llvm {
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//===----------------------------------------------------------------------===//
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// APIs for simple analysis of the loop. See header notes.
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/// getExitingBlocks - Return all blocks inside the loop that have successors
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/// outside of the loop. These are the blocks _inside of the current loop_
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/// which branch out. The returned list is always unique.
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///
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::
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getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
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typedef GraphTraits<BlockT*> BlockTraits;
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for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
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for (typename BlockTraits::ChildIteratorType I =
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BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
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I != E; ++I)
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if (!contains(*I)) {
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// Not in current loop? It must be an exit block.
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ExitingBlocks.push_back(*BI);
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break;
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}
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}
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/// getExitingBlock - If getExitingBlocks would return exactly one block,
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/// return that block. Otherwise return null.
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template<class BlockT, class LoopT>
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BlockT *LoopBase<BlockT, LoopT>::getExitingBlock() const {
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SmallVector<BlockT*, 8> ExitingBlocks;
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getExitingBlocks(ExitingBlocks);
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if (ExitingBlocks.size() == 1)
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return ExitingBlocks[0];
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return nullptr;
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}
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/// getExitBlocks - Return all of the successor blocks of this loop. These
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/// are the blocks _outside of the current loop_ which are branched to.
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///
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::
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getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
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typedef GraphTraits<BlockT*> BlockTraits;
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for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
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for (typename BlockTraits::ChildIteratorType I =
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BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
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I != E; ++I)
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if (!contains(*I))
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// Not in current loop? It must be an exit block.
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ExitBlocks.push_back(*I);
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}
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/// getExitBlock - If getExitBlocks would return exactly one block,
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/// return that block. Otherwise return null.
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template<class BlockT, class LoopT>
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BlockT *LoopBase<BlockT, LoopT>::getExitBlock() const {
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SmallVector<BlockT*, 8> ExitBlocks;
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getExitBlocks(ExitBlocks);
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if (ExitBlocks.size() == 1)
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return ExitBlocks[0];
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return nullptr;
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}
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/// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::
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getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const {
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typedef GraphTraits<BlockT*> BlockTraits;
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for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
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for (typename BlockTraits::ChildIteratorType I =
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BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
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I != E; ++I)
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if (!contains(*I))
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// Not in current loop? It must be an exit block.
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ExitEdges.push_back(Edge(*BI, *I));
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}
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/// getLoopPreheader - If there is a preheader for this loop, return it. A
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/// loop has a preheader if there is only one edge to the header of the loop
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/// from outside of the loop. If this is the case, the block branching to the
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/// header of the loop is the preheader node.
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///
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/// This method returns null if there is no preheader for the loop.
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///
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template<class BlockT, class LoopT>
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BlockT *LoopBase<BlockT, LoopT>::getLoopPreheader() const {
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// Keep track of nodes outside the loop branching to the header...
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BlockT *Out = getLoopPredecessor();
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if (!Out) return nullptr;
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// Make sure there is only one exit out of the preheader.
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typedef GraphTraits<BlockT*> BlockTraits;
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typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
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++SI;
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if (SI != BlockTraits::child_end(Out))
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return nullptr; // Multiple exits from the block, must not be a preheader.
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// The predecessor has exactly one successor, so it is a preheader.
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return Out;
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}
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/// getLoopPredecessor - If the given loop's header has exactly one unique
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/// predecessor outside the loop, return it. Otherwise return null.
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/// This is less strict that the loop "preheader" concept, which requires
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/// the predecessor to have exactly one successor.
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///
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template<class BlockT, class LoopT>
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BlockT *LoopBase<BlockT, LoopT>::getLoopPredecessor() const {
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// Keep track of nodes outside the loop branching to the header...
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BlockT *Out = nullptr;
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// Loop over the predecessors of the header node...
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BlockT *Header = getHeader();
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typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
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for (typename InvBlockTraits::ChildIteratorType PI =
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InvBlockTraits::child_begin(Header),
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PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) {
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typename InvBlockTraits::NodeType *N = *PI;
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if (!contains(N)) { // If the block is not in the loop...
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if (Out && Out != N)
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return nullptr; // Multiple predecessors outside the loop
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Out = N;
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}
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}
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// Make sure there is only one exit out of the preheader.
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assert(Out && "Header of loop has no predecessors from outside loop?");
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return Out;
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}
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/// getLoopLatch - If there is a single latch block for this loop, return it.
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/// A latch block is a block that contains a branch back to the header.
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template<class BlockT, class LoopT>
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BlockT *LoopBase<BlockT, LoopT>::getLoopLatch() const {
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BlockT *Header = getHeader();
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typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
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typename InvBlockTraits::ChildIteratorType PI =
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InvBlockTraits::child_begin(Header);
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typename InvBlockTraits::ChildIteratorType PE =
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InvBlockTraits::child_end(Header);
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BlockT *Latch = nullptr;
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for (; PI != PE; ++PI) {
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typename InvBlockTraits::NodeType *N = *PI;
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if (contains(N)) {
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if (Latch) return nullptr;
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Latch = N;
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}
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}
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return Latch;
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}
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//===----------------------------------------------------------------------===//
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// APIs for updating loop information after changing the CFG
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//
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/// addBasicBlockToLoop - This method is used by other analyses to update loop
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/// information. NewBB is set to be a new member of the current loop.
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/// Because of this, it is added as a member of all parent loops, and is added
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/// to the specified LoopInfo object as being in the current basic block. It
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/// is not valid to replace the loop header with this method.
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///
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::
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addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LIB) {
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assert((Blocks.empty() || LIB[getHeader()] == this) &&
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"Incorrect LI specified for this loop!");
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assert(NewBB && "Cannot add a null basic block to the loop!");
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assert(!LIB[NewBB] && "BasicBlock already in the loop!");
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LoopT *L = static_cast<LoopT *>(this);
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// Add the loop mapping to the LoopInfo object...
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LIB.BBMap[NewBB] = L;
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// Add the basic block to this loop and all parent loops...
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while (L) {
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L->addBlockEntry(NewBB);
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L = L->getParentLoop();
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}
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}
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/// replaceChildLoopWith - This is used when splitting loops up. It replaces
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/// the OldChild entry in our children list with NewChild, and updates the
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/// parent pointer of OldChild to be null and the NewChild to be this loop.
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/// This updates the loop depth of the new child.
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::
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replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild) {
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assert(OldChild->ParentLoop == this && "This loop is already broken!");
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assert(!NewChild->ParentLoop && "NewChild already has a parent!");
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typename std::vector<LoopT *>::iterator I =
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std::find(SubLoops.begin(), SubLoops.end(), OldChild);
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assert(I != SubLoops.end() && "OldChild not in loop!");
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*I = NewChild;
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OldChild->ParentLoop = nullptr;
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NewChild->ParentLoop = static_cast<LoopT *>(this);
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}
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/// verifyLoop - Verify loop structure
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::verifyLoop() const {
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#ifndef NDEBUG
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assert(!Blocks.empty() && "Loop header is missing");
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// Setup for using a depth-first iterator to visit every block in the loop.
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SmallVector<BlockT*, 8> ExitBBs;
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getExitBlocks(ExitBBs);
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llvm::SmallPtrSet<BlockT*, 8> VisitSet;
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VisitSet.insert(ExitBBs.begin(), ExitBBs.end());
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df_ext_iterator<BlockT*, llvm::SmallPtrSet<BlockT*, 8> >
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BI = df_ext_begin(getHeader(), VisitSet),
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BE = df_ext_end(getHeader(), VisitSet);
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// Keep track of the number of BBs visited.
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unsigned NumVisited = 0;
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// Check the individual blocks.
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for ( ; BI != BE; ++BI) {
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BlockT *BB = *BI;
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bool HasInsideLoopSuccs = false;
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bool HasInsideLoopPreds = false;
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SmallVector<BlockT *, 2> OutsideLoopPreds;
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typedef GraphTraits<BlockT*> BlockTraits;
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for (typename BlockTraits::ChildIteratorType SI =
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BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
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SI != SE; ++SI)
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if (contains(*SI)) {
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HasInsideLoopSuccs = true;
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break;
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}
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typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
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for (typename InvBlockTraits::ChildIteratorType PI =
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InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
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PI != PE; ++PI) {
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BlockT *N = *PI;
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if (contains(N))
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HasInsideLoopPreds = true;
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else
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OutsideLoopPreds.push_back(N);
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}
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if (BB == getHeader()) {
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assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
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} else if (!OutsideLoopPreds.empty()) {
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// A non-header loop shouldn't be reachable from outside the loop,
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// though it is permitted if the predecessor is not itself actually
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// reachable.
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BlockT *EntryBB = BB->getParent()->begin();
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for (BlockT *CB : depth_first(EntryBB))
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for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
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assert(CB != OutsideLoopPreds[i] &&
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"Loop has multiple entry points!");
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}
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assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
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assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
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assert(BB != getHeader()->getParent()->begin() &&
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"Loop contains function entry block!");
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NumVisited++;
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}
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assert(NumVisited == getNumBlocks() && "Unreachable block in loop");
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// Check the subloops.
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for (iterator I = begin(), E = end(); I != E; ++I)
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// Each block in each subloop should be contained within this loop.
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for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
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BI != BE; ++BI) {
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assert(contains(*BI) &&
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"Loop does not contain all the blocks of a subloop!");
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}
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// Check the parent loop pointer.
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if (ParentLoop) {
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assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) !=
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ParentLoop->end() &&
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"Loop is not a subloop of its parent!");
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}
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#endif
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}
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/// verifyLoop - Verify loop structure of this loop and all nested loops.
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::verifyLoopNest(
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DenseSet<const LoopT*> *Loops) const {
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Loops->insert(static_cast<const LoopT *>(this));
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// Verify this loop.
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verifyLoop();
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// Verify the subloops.
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for (iterator I = begin(), E = end(); I != E; ++I)
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(*I)->verifyLoopNest(Loops);
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}
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template<class BlockT, class LoopT>
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void LoopBase<BlockT, LoopT>::print(raw_ostream &OS, unsigned Depth) const {
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OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
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<< " containing: ";
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for (unsigned i = 0; i < getBlocks().size(); ++i) {
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if (i) OS << ",";
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BlockT *BB = getBlocks()[i];
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BB->printAsOperand(OS, false);
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if (BB == getHeader()) OS << "<header>";
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if (BB == getLoopLatch()) OS << "<latch>";
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if (isLoopExiting(BB)) OS << "<exiting>";
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}
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OS << "\n";
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for (iterator I = begin(), E = end(); I != E; ++I)
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(*I)->print(OS, Depth+2);
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}
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//===----------------------------------------------------------------------===//
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/// Stable LoopInfo Analysis - Build a loop tree using stable iterators so the
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/// result does / not depend on use list (block predecessor) order.
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///
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/// Discover a subloop with the specified backedges such that: All blocks within
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/// this loop are mapped to this loop or a subloop. And all subloops within this
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/// loop have their parent loop set to this loop or a subloop.
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template<class BlockT, class LoopT>
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static void discoverAndMapSubloop(LoopT *L, ArrayRef<BlockT*> Backedges,
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LoopInfoBase<BlockT, LoopT> *LI,
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DominatorTreeBase<BlockT> &DomTree) {
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typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
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unsigned NumBlocks = 0;
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unsigned NumSubloops = 0;
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// Perform a backward CFG traversal using a worklist.
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std::vector<BlockT *> ReverseCFGWorklist(Backedges.begin(), Backedges.end());
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while (!ReverseCFGWorklist.empty()) {
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BlockT *PredBB = ReverseCFGWorklist.back();
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ReverseCFGWorklist.pop_back();
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LoopT *Subloop = LI->getLoopFor(PredBB);
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if (!Subloop) {
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if (!DomTree.isReachableFromEntry(PredBB))
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continue;
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// This is an undiscovered block. Map it to the current loop.
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LI->changeLoopFor(PredBB, L);
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++NumBlocks;
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if (PredBB == L->getHeader())
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continue;
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// Push all block predecessors on the worklist.
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ReverseCFGWorklist.insert(ReverseCFGWorklist.end(),
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InvBlockTraits::child_begin(PredBB),
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InvBlockTraits::child_end(PredBB));
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}
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else {
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// This is a discovered block. Find its outermost discovered loop.
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while (LoopT *Parent = Subloop->getParentLoop())
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Subloop = Parent;
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// If it is already discovered to be a subloop of this loop, continue.
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if (Subloop == L)
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continue;
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// Discover a subloop of this loop.
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Subloop->setParentLoop(L);
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++NumSubloops;
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NumBlocks += Subloop->getBlocks().capacity();
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PredBB = Subloop->getHeader();
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// Continue traversal along predecessors that are not loop-back edges from
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// within this subloop tree itself. Note that a predecessor may directly
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// reach another subloop that is not yet discovered to be a subloop of
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// this loop, which we must traverse.
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for (typename InvBlockTraits::ChildIteratorType PI =
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InvBlockTraits::child_begin(PredBB),
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PE = InvBlockTraits::child_end(PredBB); PI != PE; ++PI) {
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if (LI->getLoopFor(*PI) != Subloop)
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ReverseCFGWorklist.push_back(*PI);
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}
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}
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}
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L->getSubLoopsVector().reserve(NumSubloops);
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L->reserveBlocks(NumBlocks);
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}
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namespace {
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/// Populate all loop data in a stable order during a single forward DFS.
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template<class BlockT, class LoopT>
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class PopulateLoopsDFS {
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typedef GraphTraits<BlockT*> BlockTraits;
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typedef typename BlockTraits::ChildIteratorType SuccIterTy;
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LoopInfoBase<BlockT, LoopT> *LI;
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DenseSet<const BlockT *> VisitedBlocks;
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std::vector<std::pair<BlockT*, SuccIterTy> > DFSStack;
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public:
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PopulateLoopsDFS(LoopInfoBase<BlockT, LoopT> *li):
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LI(li) {}
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void traverse(BlockT *EntryBlock);
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protected:
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void insertIntoLoop(BlockT *Block);
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BlockT *dfsSource() { return DFSStack.back().first; }
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SuccIterTy &dfsSucc() { return DFSStack.back().second; }
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SuccIterTy dfsSuccEnd() { return BlockTraits::child_end(dfsSource()); }
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void pushBlock(BlockT *Block) {
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DFSStack.push_back(std::make_pair(Block, BlockTraits::child_begin(Block)));
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}
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};
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} // anonymous
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/// Top-level driver for the forward DFS within the loop.
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template<class BlockT, class LoopT>
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void PopulateLoopsDFS<BlockT, LoopT>::traverse(BlockT *EntryBlock) {
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pushBlock(EntryBlock);
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VisitedBlocks.insert(EntryBlock);
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while (!DFSStack.empty()) {
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// Traverse the leftmost path as far as possible.
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while (dfsSucc() != dfsSuccEnd()) {
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BlockT *BB = *dfsSucc();
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++dfsSucc();
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if (!VisitedBlocks.insert(BB).second)
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continue;
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// Push the next DFS successor onto the stack.
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pushBlock(BB);
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}
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// Visit the top of the stack in postorder and backtrack.
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insertIntoLoop(dfsSource());
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DFSStack.pop_back();
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}
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}
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/// Add a single Block to its ancestor loops in PostOrder. If the block is a
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/// subloop header, add the subloop to its parent in PostOrder, then reverse the
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/// Block and Subloop vectors of the now complete subloop to achieve RPO.
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template<class BlockT, class LoopT>
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void PopulateLoopsDFS<BlockT, LoopT>::insertIntoLoop(BlockT *Block) {
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LoopT *Subloop = LI->getLoopFor(Block);
|
|
if (Subloop && Block == Subloop->getHeader()) {
|
|
// We reach this point once per subloop after processing all the blocks in
|
|
// the subloop.
|
|
if (Subloop->getParentLoop())
|
|
Subloop->getParentLoop()->getSubLoopsVector().push_back(Subloop);
|
|
else
|
|
LI->addTopLevelLoop(Subloop);
|
|
|
|
// For convenience, Blocks and Subloops are inserted in postorder. Reverse
|
|
// the lists, except for the loop header, which is always at the beginning.
|
|
Subloop->reverseBlock(1);
|
|
std::reverse(Subloop->getSubLoopsVector().begin(),
|
|
Subloop->getSubLoopsVector().end());
|
|
|
|
Subloop = Subloop->getParentLoop();
|
|
}
|
|
for (; Subloop; Subloop = Subloop->getParentLoop())
|
|
Subloop->addBlockEntry(Block);
|
|
}
|
|
|
|
/// Analyze LoopInfo discovers loops during a postorder DominatorTree traversal
|
|
/// interleaved with backward CFG traversals within each subloop
|
|
/// (discoverAndMapSubloop). The backward traversal skips inner subloops, so
|
|
/// this part of the algorithm is linear in the number of CFG edges. Subloop and
|
|
/// Block vectors are then populated during a single forward CFG traversal
|
|
/// (PopulateLoopDFS).
|
|
///
|
|
/// During the two CFG traversals each block is seen three times:
|
|
/// 1) Discovered and mapped by a reverse CFG traversal.
|
|
/// 2) Visited during a forward DFS CFG traversal.
|
|
/// 3) Reverse-inserted in the loop in postorder following forward DFS.
|
|
///
|
|
/// The Block vectors are inclusive, so step 3 requires loop-depth number of
|
|
/// insertions per block.
|
|
template<class BlockT, class LoopT>
|
|
void LoopInfoBase<BlockT, LoopT>::
|
|
Analyze(DominatorTreeBase<BlockT> &DomTree) {
|
|
|
|
// Postorder traversal of the dominator tree.
|
|
DomTreeNodeBase<BlockT>* DomRoot = DomTree.getRootNode();
|
|
for (po_iterator<DomTreeNodeBase<BlockT>*> DomIter = po_begin(DomRoot),
|
|
DomEnd = po_end(DomRoot); DomIter != DomEnd; ++DomIter) {
|
|
|
|
BlockT *Header = DomIter->getBlock();
|
|
SmallVector<BlockT *, 4> Backedges;
|
|
|
|
// Check each predecessor of the potential loop header.
|
|
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
|
|
for (typename InvBlockTraits::ChildIteratorType PI =
|
|
InvBlockTraits::child_begin(Header),
|
|
PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) {
|
|
|
|
BlockT *Backedge = *PI;
|
|
|
|
// If Header dominates predBB, this is a new loop. Collect the backedges.
|
|
if (DomTree.dominates(Header, Backedge)
|
|
&& DomTree.isReachableFromEntry(Backedge)) {
|
|
Backedges.push_back(Backedge);
|
|
}
|
|
}
|
|
// Perform a backward CFG traversal to discover and map blocks in this loop.
|
|
if (!Backedges.empty()) {
|
|
LoopT *L = new LoopT(Header);
|
|
discoverAndMapSubloop(L, ArrayRef<BlockT*>(Backedges), this, DomTree);
|
|
}
|
|
}
|
|
// Perform a single forward CFG traversal to populate block and subloop
|
|
// vectors for all loops.
|
|
PopulateLoopsDFS<BlockT, LoopT> DFS(this);
|
|
DFS.traverse(DomRoot->getBlock());
|
|
}
|
|
|
|
// Debugging
|
|
template<class BlockT, class LoopT>
|
|
void LoopInfoBase<BlockT, LoopT>::print(raw_ostream &OS) const {
|
|
for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
|
|
TopLevelLoops[i]->print(OS);
|
|
#if 0
|
|
for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
|
|
E = BBMap.end(); I != E; ++I)
|
|
OS << "BB '" << I->first->getName() << "' level = "
|
|
<< I->second->getLoopDepth() << "\n";
|
|
#endif
|
|
}
|
|
|
|
template<class BlockT, class LoopT>
|
|
void LoopInfoBase<BlockT, LoopT>::verify() const {
|
|
DenseSet<const LoopT*> Loops;
|
|
for (iterator I = begin(), E = end(); I != E; ++I) {
|
|
assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
|
|
(*I)->verifyLoopNest(&Loops);
|
|
}
|
|
|
|
// Verify that blocks are mapped to valid loops.
|
|
#ifndef NDEBUG
|
|
for (auto &Entry : BBMap) {
|
|
BlockT *BB = Entry.first;
|
|
LoopT *L = Entry.second;
|
|
assert(Loops.count(L) && "orphaned loop");
|
|
assert(L->contains(BB) && "orphaned block");
|
|
}
|
|
#endif
|
|
}
|
|
|
|
} // End llvm namespace
|
|
|
|
#endif
|