llvm-6502/include/llvm/Transforms/Utils/BasicBlockUtils.h
Chandler Carruth 10b853882c [PM] Replace the Pass argument to SplitEdge with specific analyses used
and updated.

This may appear to remove handling for things like alias analysis when
splitting critical edges here, but in fact no callers of SplitEdge
relied on this. Similarly, all of them wanted to preserve LCSSA if there
was any update of the loop info. That makes the interface much simpler.

With this, all of BasicBlockUtils.h is free of Pass arguments and
prepared for the new pass manager. This is tho majority of utilities
that relied on pass arguments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226459 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-19 12:36:53 +00:00

310 lines
13 KiB
C++

//===-- 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_BASICBLOCKUTILS_H
#define LLVM_TRANSFORMS_UTILS_BASICBLOCKUTILS_H
// FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
namespace llvm {
class AliasAnalysis;
class MemoryDependenceAnalysis;
class DominatorTree;
class LoopInfo;
class Instruction;
class MDNode;
class ReturnInst;
class TargetLibraryInfo;
class TerminatorInst;
/// 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, AliasAnalysis *AA = nullptr,
MemoryDependenceAnalysis *MemDep = nullptr);
/// 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, const TargetLibraryInfo *TLI = nullptr);
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
bool MergeBlockIntoPredecessor(BasicBlock *BB, DominatorTree *DT = nullptr,
LoopInfo *LI = nullptr,
AliasAnalysis *AA = nullptr,
MemoryDependenceAnalysis *MemDep = nullptr);
// 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);
/// \brief Option class for critical edge splitting.
///
/// This provides a builder interface for overriding the default options used
/// during critical edge splitting.
struct CriticalEdgeSplittingOptions {
AliasAnalysis *AA;
DominatorTree *DT;
LoopInfo *LI;
bool MergeIdenticalEdges;
bool DontDeleteUselessPHIs;
bool PreserveLCSSA;
CriticalEdgeSplittingOptions()
: AA(nullptr), DT(nullptr), LI(nullptr), MergeIdenticalEdges(false),
DontDeleteUselessPHIs(false), PreserveLCSSA(false) {}
/// \brief Basic case of setting up all the analysis.
CriticalEdgeSplittingOptions(AliasAnalysis *AA, DominatorTree *DT = nullptr,
LoopInfo *LI = nullptr)
: AA(AA), DT(DT), LI(LI), MergeIdenticalEdges(false),
DontDeleteUselessPHIs(false), PreserveLCSSA(false) {}
/// \brief A common pattern is to preserve the dominator tree and loop
/// info but not care about AA.
CriticalEdgeSplittingOptions(DominatorTree *DT, LoopInfo *LI)
: AA(nullptr), DT(DT), LI(LI), MergeIdenticalEdges(false),
DontDeleteUselessPHIs(false), PreserveLCSSA(false) {}
CriticalEdgeSplittingOptions &setMergeIdenticalEdges() {
MergeIdenticalEdges = true;
return *this;
}
CriticalEdgeSplittingOptions &setDontDeleteUselessPHIs() {
DontDeleteUselessPHIs = true;
return *this;
}
CriticalEdgeSplittingOptions &setPreserveLCSSA() {
PreserveLCSSA = true;
return *this;
}
};
/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge. This will update the analyses passed in through
/// the option struct. This returns the new block if the edge was split, null
/// otherwise.
///
/// If MergeIdenticalEdges in the options struct 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,
const CriticalEdgeSplittingOptions &Options =
CriticalEdgeSplittingOptions());
inline BasicBlock *
SplitCriticalEdge(BasicBlock *BB, succ_iterator SI,
const CriticalEdgeSplittingOptions &Options =
CriticalEdgeSplittingOptions()) {
return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(),
Options);
}
/// 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,
const CriticalEdgeSplittingOptions &Options =
CriticalEdgeSplittingOptions()) {
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, Options);
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. It updates the analyses
/// passed in the options struct
inline BasicBlock *
SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst,
const CriticalEdgeSplittingOptions &Options =
CriticalEdgeSplittingOptions()) {
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, Options);
++i;
}
}
// SplitAllCriticalEdges - Loop over all of the edges in the CFG,
// breaking critical edges as they are found.
// Returns the number of broken edges.
unsigned SplitAllCriticalEdges(Function &F,
const CriticalEdgeSplittingOptions &Options =
CriticalEdgeSplittingOptions());
/// SplitEdge - Split the edge connecting specified block.
BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To,
DominatorTree *DT = nullptr, LoopInfo *LI = nullptr);
/// 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,
DominatorTree *DT = nullptr, LoopInfo *LI = nullptr);
/// 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, ArrayRef<BasicBlock *> Preds,
const char *Suffix,
AliasAnalysis *AA = nullptr,
DominatorTree *DT = nullptr,
LoopInfo *LI = nullptr,
bool PreserveLCSSA = false);
/// 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,
SmallVectorImpl<BasicBlock *> &NewBBs,
AliasAnalysis *AA = nullptr,
DominatorTree *DT = nullptr,
LoopInfo *LI = nullptr,
bool PreserveLCSSA = false);
/// 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);
/// SplitBlockAndInsertIfThen - Split the containing block at the
/// specified instruction - everything before and including SplitBefore stays
/// in the old basic block, and everything after SplitBefore is moved to a
/// new block. The two blocks are connected by a conditional branch
/// (with value of Cmp being the condition).
/// Before:
/// Head
/// SplitBefore
/// Tail
/// After:
/// Head
/// if (Cond)
/// ThenBlock
/// SplitBefore
/// Tail
///
/// If Unreachable is true, then ThenBlock ends with
/// UnreachableInst, otherwise it branches to Tail.
/// Returns the NewBasicBlock's terminator.
///
/// Updates DT if given.
TerminatorInst *SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore,
bool Unreachable,
MDNode *BranchWeights = nullptr,
DominatorTree *DT = nullptr);
/// SplitBlockAndInsertIfThenElse is similar to SplitBlockAndInsertIfThen,
/// but also creates the ElseBlock.
/// Before:
/// Head
/// SplitBefore
/// Tail
/// After:
/// Head
/// if (Cond)
/// ThenBlock
/// else
/// ElseBlock
/// SplitBefore
/// Tail
void SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore,
TerminatorInst **ThenTerm,
TerminatorInst **ElseTerm,
MDNode *BranchWeights = nullptr);
///
/// GetIfCondition - Check whether BB is the merge point of a if-region.
/// If so, return the boolean condition that determines which entry into
/// BB will be taken. Also, return by references the block that will be
/// entered from if the condition is true, and the block that will be
/// entered if the condition is false.
Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
BasicBlock *&IfFalse);
} // End llvm namespace
#endif