1 //===-- Transform/Utils/BasicBlockUtils.h - BasicBlock Utils ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This family of functions perform manipulations on basic blocks, and
11 // instructions contained within basic blocks.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_TRANSFORMS_UTILS_BASICBLOCK_H
16 #define LLVM_TRANSFORMS_UTILS_BASICBLOCK_H
18 // FIXME: Move to this file: BasicBlock::removePredecessor, BB::splitBasicBlock
20 #include "llvm/BasicBlock.h"
21 #include "llvm/Support/CFG.h"
28 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
29 // with a value, then remove and delete the original instruction.
31 void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
32 BasicBlock::iterator &BI, Value *V);
34 // ReplaceInstWithInst - Replace the instruction specified by BI with the
35 // instruction specified by I. The original instruction is deleted and BI is
36 // updated to point to the new instruction.
38 void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
39 BasicBlock::iterator &BI, Instruction *I);
41 // ReplaceInstWithInst - Replace the instruction specified by From with the
42 // instruction specified by To.
44 void ReplaceInstWithInst(Instruction *From, Instruction *To);
47 // RemoveSuccessor - Change the specified terminator instruction such that its
48 // successor #SuccNum no longer exists. Because this reduces the outgoing
49 // degree of the current basic block, the actual terminator instruction itself
50 // may have to be changed. In the case where the last successor of the block is
51 // deleted, a return instruction is inserted in its place which can cause a
52 // suprising change in program behavior if it is not expected.
54 void RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum);
56 /// isCriticalEdge - Return true if the specified edge is a critical edge.
57 /// Critical edges are edges from a block with multiple successors to a block
58 /// with multiple predecessors.
60 bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
61 bool AllowIdenticalEdges = false);
63 /// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
64 /// split the critical edge. This will update DominatorTree and
65 /// DominatorFrontier information if it is available, thus calling this pass
66 /// will not invalidate either of them. This returns true if the edge was split,
69 /// If MergeIdenticalEdges is true (the default), *all* edges from TI to the
70 /// specified successor will be merged into the same critical edge block.
71 /// This is most commonly interesting with switch instructions, which may
72 /// have many edges to any one destination. This ensures that all edges to that
73 /// dest go to one block instead of each going to a different block, but isn't
74 /// the standard definition of a "critical edge".
76 bool SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P = 0,
77 bool MergeIdenticalEdges = false);
79 inline bool SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, Pass *P = 0) {
80 return SplitCriticalEdge(BB->getTerminator(), SI.getSuccessorIndex(), P);
83 /// SplitCriticalEdge - If the edge from *PI to BB is not critical, return
84 /// false. Otherwise, split all edges between the two blocks and return true.
85 /// This updates all of the same analyses as the other SplitCriticalEdge
86 /// function. If P is specified, it updates the analyses
88 inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, Pass *P = 0) {
89 bool MadeChange = false;
90 TerminatorInst *TI = (*PI)->getTerminator();
91 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
92 if (TI->getSuccessor(i) == Succ)
93 MadeChange |= SplitCriticalEdge(TI, i, P);
97 /// SplitCriticalEdge - If an edge from Src to Dst is critical, split the edge
98 /// and return true, otherwise return false. This method requires that there be
99 /// an edge between the two blocks. If P is specified, it updates the analyses
101 inline bool SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst, Pass *P = 0,
102 bool MergeIdenticalEdges = false) {
103 TerminatorInst *TI = Src->getTerminator();
106 assert(i != TI->getNumSuccessors() && "Edge doesn't exist!");
107 if (TI->getSuccessor(i) == Dst)
108 return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges);
113 /// SplitEdge - Split the edge connecting specified block. Pass P must
115 BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P);
117 /// SplitBlock - Split the specified block at the specified instruction - every
118 /// thing before SplitPt stays in Old and everything starting with SplitPt moves
119 /// to a new block. The two blocks are joined by an unconditional branch and
120 /// the loop info is updated.
122 BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P);
123 } // End llvm namespace