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authored <ed@FreeBSD.org>2009-06-02 17:52:33 +0000
committered <ed@FreeBSD.org>2009-06-02 17:52:33 +0000
commit3277b69d734b9c90b44ebde4ede005717e2c3b2e (patch)
tree64ba909838c23261cace781ece27d106134ea451 /include/llvm/Transforms/Utils/BasicBlockUtils.h
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Import LLVM, at r72732.
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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"
+
+namespace llvm {
+
+class Instruction;
+class Pass;
+class AliasAnalysis;
+
+/// 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);
+
+/// 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.
+void 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);
+
+/// CopyPrecedingStopPoint - If I is immediately preceded by a StopPoint,
+/// make a copy of the stoppoint before InsertPos (presumably before copying
+/// or moving I).
+void CopyPrecedingStopPoint(Instruction *I, BasicBlock::iterator InsertPos);
+
+/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the
+/// instruction before ScanFrom) checking to see if we have the value at the
+/// memory address *Ptr locally available within a small number of instructions.
+/// If the value is available, return it.
+///
+/// If not, return the iterator for the last validated instruction that the
+/// value would be live through. If we scanned the entire block and didn't find
+/// something that invalidates *Ptr or provides it, ScanFrom would be left at
+/// begin() and this returns null. ScanFrom could also be left
+///
+/// MaxInstsToScan specifies the maximum instructions to scan in the block. If
+/// it is set to 0, it will scan the whole block. You can also optionally
+/// specify an alias analysis implementation, which makes this more precise.
+Value *FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
+ BasicBlock::iterator &ScanFrom,
+ unsigned MaxInstsToScan = 6,
+ AliasAnalysis *AA = 0);
+
+/// 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);
+
+
+// RemoveSuccessor - Change the specified terminator instruction such that its
+// successor #SuccNum no longer exists. Because this reduces the outgoing
+// degree of the current basic block, the actual terminator instruction itself
+// may have to be changed. In the case where the last successor of the block is
+// deleted, a return instruction is inserted in its place which can cause a
+// suprising change in program behavior if it is not expected.
+//
+void RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum);
+
+/// 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 true if the edge was split,
+/// false 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".
+///
+bool SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P = 0,
+ bool MergeIdenticalEdges = false);
+
+inline bool 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 bool SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst, Pass *P = 0,
+ bool MergeIdenticalEdges = 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);
+ ++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 and
+/// DominanceFrontier, but no other analyses.
+BasicBlock *SplitBlockPredecessors(BasicBlock *BB, BasicBlock *const *Preds,
+ unsigned NumPreds, const char *Suffix,
+ Pass *P = 0);
+
+} // End llvm namespace
+
+#endif
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