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14cb183214
Differential revision: https://reviews.llvm.org/D23675 llvm-svn: 279102
291 lines
12 KiB
C++
291 lines
12 KiB
C++
//===-- Transform/Utils/BasicBlockUtils.h - BasicBlock Utils ----*- 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 family of functions perform manipulations on basic blocks, and
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// instructions contained within basic blocks.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
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#define LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
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// FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/InstrTypes.h"
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#include <cassert>
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namespace llvm {
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class MemoryDependenceResults;
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class DominatorTree;
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class LoopInfo;
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class Instruction;
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class MDNode;
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class ReturnInst;
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class TargetLibraryInfo;
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/// Delete the specified block, which must have no predecessors.
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void DeleteDeadBlock(BasicBlock *BB);
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/// We know that BB has one predecessor. If there are any single-entry PHI nodes
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/// in it, fold them away. This handles the case when all entries to the PHI
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/// nodes in a block are guaranteed equal, such as when the block has exactly
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/// one predecessor.
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void FoldSingleEntryPHINodes(BasicBlock *BB,
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MemoryDependenceResults *MemDep = nullptr);
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/// Examine each PHI in the given block and delete it if it is dead. Also
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/// recursively delete any operands that become dead as a result. This includes
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/// tracing the def-use list from the PHI to see if it is ultimately unused or
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/// if it reaches an unused cycle. Return true if any PHIs were deleted.
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bool DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI = nullptr);
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/// Attempts to merge a block into its predecessor, if possible. The return
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/// value indicates success or failure.
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bool MergeBlockIntoPredecessor(BasicBlock *BB, DominatorTree *DT = nullptr,
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LoopInfo *LI = nullptr,
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MemoryDependenceResults *MemDep = nullptr);
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/// Replace all uses of an instruction (specified by BI) with a value, then
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/// remove and delete the original instruction.
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void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
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BasicBlock::iterator &BI, Value *V);
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/// Replace the instruction specified by BI with the instruction specified by I.
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/// Copies DebugLoc from BI to I, if I doesn't already have a DebugLoc. The
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/// original instruction is deleted and BI is updated to point to the new
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/// instruction.
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void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
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BasicBlock::iterator &BI, Instruction *I);
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/// Replace the instruction specified by From with the instruction specified by
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/// To. Copies DebugLoc from BI to I, if I doesn't already have a DebugLoc.
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void ReplaceInstWithInst(Instruction *From, Instruction *To);
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/// Option class for critical edge splitting.
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///
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/// This provides a builder interface for overriding the default options used
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/// during critical edge splitting.
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struct CriticalEdgeSplittingOptions {
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DominatorTree *DT;
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LoopInfo *LI;
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bool MergeIdenticalEdges;
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bool DontDeleteUselessPHIs;
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bool PreserveLCSSA;
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CriticalEdgeSplittingOptions(DominatorTree *DT = nullptr,
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LoopInfo *LI = nullptr)
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: DT(DT), LI(LI), MergeIdenticalEdges(false),
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DontDeleteUselessPHIs(false), PreserveLCSSA(false) {}
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CriticalEdgeSplittingOptions &setMergeIdenticalEdges() {
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MergeIdenticalEdges = true;
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return *this;
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}
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CriticalEdgeSplittingOptions &setDontDeleteUselessPHIs() {
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DontDeleteUselessPHIs = true;
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return *this;
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}
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CriticalEdgeSplittingOptions &setPreserveLCSSA() {
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PreserveLCSSA = true;
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return *this;
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}
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};
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/// If this edge is a critical edge, insert a new node to split the critical
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/// edge. This will update the analyses passed in through the option struct.
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/// This returns the new block if the edge was split, null otherwise.
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///
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/// If MergeIdenticalEdges in the options struct is true (not the default),
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/// *all* edges from TI to the specified successor will be merged into the same
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/// critical edge block. This is most commonly interesting with switch
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/// instructions, which may have many edges to any one destination. This
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/// ensures that all edges to that dest go to one block instead of each going
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/// to a different block, but isn't the standard definition of a "critical
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/// edge".
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///
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/// It is invalid to call this function on a critical edge that starts at an
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/// IndirectBrInst. Splitting these edges will almost always create an invalid
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/// program because the address of the new block won't be the one that is jumped
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/// to.
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///
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BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
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const CriticalEdgeSplittingOptions &Options =
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CriticalEdgeSplittingOptions());
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inline BasicBlock *
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SplitCriticalEdge(BasicBlock *BB, succ_iterator SI,
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const CriticalEdgeSplittingOptions &Options =
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CriticalEdgeSplittingOptions()) {
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return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(),
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Options);
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}
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/// If the edge from *PI to BB is not critical, return false. Otherwise, split
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/// all edges between the two blocks and return true. This updates all of the
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/// same analyses as the other SplitCriticalEdge function. If P is specified, it
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/// updates the analyses described above.
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inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI,
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const CriticalEdgeSplittingOptions &Options =
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CriticalEdgeSplittingOptions()) {
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bool MadeChange = false;
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TerminatorInst *TI = (*PI)->getTerminator();
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for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
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if (TI->getSuccessor(i) == Succ)
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MadeChange |= !!SplitCriticalEdge(TI, i, Options);
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return MadeChange;
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}
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/// If an edge from Src to Dst is critical, split the edge and return true,
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/// otherwise return false. This method requires that there be an edge between
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/// the two blocks. It updates the analyses passed in the options struct
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inline BasicBlock *
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SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst,
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const CriticalEdgeSplittingOptions &Options =
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CriticalEdgeSplittingOptions()) {
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TerminatorInst *TI = Src->getTerminator();
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unsigned i = 0;
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while (true) {
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assert(i != TI->getNumSuccessors() && "Edge doesn't exist!");
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if (TI->getSuccessor(i) == Dst)
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return SplitCriticalEdge(TI, i, Options);
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++i;
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}
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}
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/// Loop over all of the edges in the CFG, breaking critical edges as they are
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/// found. Returns the number of broken edges.
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unsigned SplitAllCriticalEdges(Function &F,
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const CriticalEdgeSplittingOptions &Options =
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CriticalEdgeSplittingOptions());
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/// Split the edge connecting specified block.
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BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To,
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DominatorTree *DT = nullptr, LoopInfo *LI = nullptr);
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/// Split the specified block at the specified instruction - everything before
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/// SplitPt stays in Old and everything starting with SplitPt moves to a new
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/// block. The two blocks are joined by an unconditional branch and the loop
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/// info is updated.
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BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt,
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DominatorTree *DT = nullptr, LoopInfo *LI = nullptr);
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/// This method introduces at least one new basic block into the function and
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/// moves some of the predecessors of BB to be predecessors of the new block.
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/// The new predecessors are indicated by the Preds array. The new block is
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/// given a suffix of 'Suffix'. Returns new basic block to which predecessors
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/// from Preds are now pointing.
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///
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/// If BB is a landingpad block then additional basicblock might be introduced.
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/// It will have Suffix+".split_lp". See SplitLandingPadPredecessors for more
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/// details on this case.
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///
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/// This currently updates the LLVM IR, DominatorTree, LoopInfo, and LCCSA but
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/// no other analyses. In particular, it does not preserve LoopSimplify
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/// (because it's complicated to handle the case where one of the edges being
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/// split is an exit of a loop with other exits).
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///
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BasicBlock *SplitBlockPredecessors(BasicBlock *BB, ArrayRef<BasicBlock *> Preds,
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const char *Suffix,
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DominatorTree *DT = nullptr,
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LoopInfo *LI = nullptr,
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bool PreserveLCSSA = false);
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/// This method transforms the landing pad, OrigBB, by introducing two new basic
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/// blocks into the function. One of those new basic blocks gets the
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/// predecessors listed in Preds. The other basic block gets the remaining
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/// predecessors of OrigBB. The landingpad instruction OrigBB is clone into both
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/// of the new basic blocks. The new blocks are given the suffixes 'Suffix1' and
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/// 'Suffix2', and are returned in the NewBBs vector.
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///
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/// This currently updates the LLVM IR, DominatorTree, LoopInfo, and LCCSA but
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/// no other analyses. In particular, it does not preserve LoopSimplify
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/// (because it's complicated to handle the case where one of the edges being
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/// split is an exit of a loop with other exits).
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///
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void SplitLandingPadPredecessors(BasicBlock *OrigBB,
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ArrayRef<BasicBlock *> Preds,
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const char *Suffix, const char *Suffix2,
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SmallVectorImpl<BasicBlock *> &NewBBs,
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DominatorTree *DT = nullptr,
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LoopInfo *LI = nullptr,
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bool PreserveLCSSA = false);
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/// This method duplicates the specified return instruction into a predecessor
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/// which ends in an unconditional branch. If the return instruction returns a
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/// value defined by a PHI, propagate the right value into the return. It
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/// returns the new return instruction in the predecessor.
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ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
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BasicBlock *Pred);
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/// Split the containing block at the specified instruction - everything before
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/// and including SplitBefore stays in the old basic block, and everything after
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/// SplitBefore is moved to a new block. The two blocks are connected by a
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/// conditional branch (with value of Cmp being the condition).
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/// Before:
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/// Head
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/// SplitBefore
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/// Tail
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/// After:
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/// Head
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/// if (Cond)
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/// ThenBlock
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/// SplitBefore
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/// Tail
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///
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/// If Unreachable is true, then ThenBlock ends with
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/// UnreachableInst, otherwise it branches to Tail.
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/// Returns the NewBasicBlock's terminator.
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///
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/// Updates DT and LI if given.
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TerminatorInst *SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore,
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bool Unreachable,
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MDNode *BranchWeights = nullptr,
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DominatorTree *DT = nullptr,
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LoopInfo *LI = nullptr);
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/// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen,
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/// but also creates the ElseBlock.
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/// Before:
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/// Head
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/// SplitBefore
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/// Tail
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/// After:
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/// Head
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/// if (Cond)
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/// ThenBlock
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/// else
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/// ElseBlock
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/// SplitBefore
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/// Tail
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void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore,
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TerminatorInst **ThenTerm,
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TerminatorInst **ElseTerm,
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MDNode *BranchWeights = nullptr);
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/// Check whether BB is the merge point of a if-region.
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/// If so, return the boolean condition that determines which entry into
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/// BB will be taken. Also, return by references the block that will be
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/// entered from if the condition is true, and the block that will be
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/// entered if the condition is false.
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///
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/// This does no checking to see if the true/false blocks have large or unsavory
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/// instructions in them.
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Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
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BasicBlock *&IfFalse);
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
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