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//===-- Transform/Utils/BasicBlockUtils.h - BasicBlock Utils ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This family of functions perform manipulations on basic blocks, and
// instructions contained within basic blocks.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_UTILS_BASICBLOCK_H
#define LLVM_TRANSFORMS_UTILS_BASICBLOCK_H
// FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock
#include "llvm/BasicBlock.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/DebugLoc.h"
namespace llvm {
class AliasAnalysis;
class Instruction;
class Pass;
class ReturnInst;
/// DeleteDeadBlock - Delete the specified block, which must have no
/// predecessors.
void DeleteDeadBlock(BasicBlock *BB);
/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
/// any single-entry PHI nodes in it, fold them away. This handles the case
/// when all entries to the PHI nodes in a block are guaranteed equal, such as
/// when the block has exactly one predecessor.
void FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P = 0);
/// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
/// is dead. Also recursively delete any operands that become dead as
/// a result. This includes tracing the def-use list from the PHI to see if
/// it is ultimately unused or if it reaches an unused cycle. Return true
/// if any PHIs were deleted.
bool DeleteDeadPHIs(BasicBlock *BB);
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
bool MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P = 0);
// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
// with a value, then remove and delete the original instruction.
//
void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Value *V);
// ReplaceInstWithInst - Replace the instruction specified by BI with the
// instruction specified by I. The original instruction is deleted and BI is
// updated to point to the new instruction.
//
void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
BasicBlock::iterator &BI, Instruction *I);
// ReplaceInstWithInst - Replace the instruction specified by From with the
// instruction specified by To.
//
void ReplaceInstWithInst(Instruction *From, Instruction *To);
/// FindFunctionBackedges - Analyze the specified function to find all of the
/// loop backedges in the function and return them. This is a relatively cheap
/// (compared to computing dominators and loop info) analysis.
///
/// The output is added to Result, as pairs of <from,to> edge info.
void FindFunctionBackedges(const Function &F,
SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result);
/// GetSuccessorNumber - Search for the specified successor of basic block BB
/// and return its position in the terminator instruction's list of
/// successors. It is an error to call this with a block that is not a
/// successor.
unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ);
/// isCriticalEdge - Return true if the specified edge is a critical edge.
/// Critical edges are edges from a block with multiple successors to a block
/// with multiple predecessors.
///
bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
bool AllowIdenticalEdges = false);
/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge. This will update DominatorTree and
/// DominatorFrontier information if it is available, thus calling this pass
/// will not invalidate either of them. This returns the new block if the edge
/// was split, null otherwise.
///
/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
/// specified successor will be merged into the same critical edge block.
/// This is most commonly interesting with switch instructions, which may
/// have many edges to any one destination. This ensures that all edges to that
/// dest go to one block instead of each going to a different block, but isn't
/// the standard definition of a "critical edge".
///
/// It is invalid to call this function on a critical edge that starts at an
/// IndirectBrInst. Splitting these edges will almost always create an invalid
/// program because the address of the new block won't be the one that is jumped
/// to.
///
BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
Pass *P = 0, bool MergeIdenticalEdges = false,
bool DontDeleteUselessPHIs = false);
inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI,
Pass *P = 0) {
return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P);
}
/// SplitCriticalEdge - If the edge from *PI to BB is not critical, return
/// false. Otherwise, split all edges between the two blocks and return true.
/// This updates all of the same analyses as the other SplitCriticalEdge
/// function. If P is specified, it updates the analyses
/// described above.
inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, Pass *P = 0) {
bool MadeChange = false;
TerminatorInst *TI = (*PI)->getTerminator();
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
if (TI->getSuccessor(i) == Succ)
MadeChange |= !!SplitCriticalEdge(TI, i, P);
return MadeChange;
}
/// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge
/// and return true, otherwise return false. This method requires that there be
/// an edge between the two blocks. If P is specified, it updates the analyses
/// described above.
inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst,
Pass *P = 0,
bool MergeIdenticalEdges = false,
bool DontDeleteUselessPHIs = false) {
TerminatorInst *TI = Src->getTerminator();
unsigned i = 0;
while (1) {
assert(i != TI->getNumSuccessors() && "Edge doesn't exist!");
if (TI->getSuccessor(i) == Dst)
return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges,
DontDeleteUselessPHIs);
++i;
}
}
/// SplitEdge - Split the edge connecting specified block. Pass P must
/// not be NULL.
BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P);
/// SplitBlock - Split the specified block at the specified instruction - every
/// thing before SplitPt stays in Old and everything starting with SplitPt moves
/// to a new block. The two blocks are joined by an unconditional branch and
/// the loop info is updated.
///
BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P);
/// SplitBlockPredecessors - This method transforms BB by introducing a new
/// basic block into the function, and moving some of the predecessors of BB to
/// be predecessors of the new block. The new predecessors are indicated by the
/// Preds array, which has NumPreds elements in it. The new block is given a
/// suffix of 'Suffix'. This function returns the new block.
///
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
/// In particular, it does not preserve LoopSimplify (because it's
/// complicated to handle the case where one of the edges being split
/// is an exit of a loop with other exits).
///
BasicBlock *SplitBlockPredecessors(BasicBlock *BB, BasicBlock *const *Preds,
unsigned NumPreds, const char *Suffix,
Pass *P = 0);
/// SplitLandingPadPredecessors - This method transforms the landing pad,
/// OrigBB, by introducing two new basic blocks into the function. One of those
/// new basic blocks gets the predecessors listed in Preds. The other basic
/// block gets the remaining predecessors of OrigBB. The landingpad instruction
/// OrigBB is clone into both of the new basic blocks. The new blocks are given
/// the suffixes 'Suffix1' and 'Suffix2', and are returned in the NewBBs vector.
///
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. In particular,
/// it does not preserve LoopSimplify (because it's complicated to handle the
/// case where one of the edges being split is an exit of a loop with other
/// exits).
///
void SplitLandingPadPredecessors(BasicBlock *OrigBB,ArrayRef<BasicBlock*> Preds,
const char *Suffix, const char *Suffix2,
Pass *P, SmallVectorImpl<BasicBlock*> &NewBBs);
/// FoldReturnIntoUncondBranch - This method duplicates the specified return
/// instruction into a predecessor which ends in an unconditional branch. If
/// the return instruction returns a value defined by a PHI, propagate the
/// right value into the return. It returns the new return instruction in the
/// predecessor.
ReturnInst *FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
BasicBlock *Pred);
/// GetFirstDebugLocInBasicBlock - Return first valid DebugLoc entry in a
/// given basic block.
DebugLoc GetFirstDebugLocInBasicBlock(const BasicBlock *BB);
} // End llvm namespace
#endif
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