1 //===-- Local.h - Functions to perform local transformations ----*- 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 various local transformations to the
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H
16 #define LLVM_TRANSFORMS_UTILS_LOCAL_H
29 template<typename T> class SmallVectorImpl;
31 //===----------------------------------------------------------------------===//
32 // Local constant propagation.
35 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
36 /// constant value, convert it into an unconditional branch to the constant
37 /// destination. This is a nontrivial operation because the successors of this
38 /// basic block must have their PHI nodes updated.
40 bool ConstantFoldTerminator(BasicBlock *BB);
42 //===----------------------------------------------------------------------===//
43 // Local dead code elimination.
46 /// isInstructionTriviallyDead - Return true if the result produced by the
47 /// instruction is not used, and the instruction has no side effects.
49 bool isInstructionTriviallyDead(Instruction *I);
52 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
53 /// trivially dead instruction, delete it. If that makes any of its operands
54 /// trivially dead, delete them too, recursively.
56 /// If DeadInst is specified, the vector is filled with the instructions that
57 /// are actually deleted.
58 void RecursivelyDeleteTriviallyDeadInstructions(Value *V,
59 SmallVectorImpl<Instruction*> *DeadInst = 0);
61 //===----------------------------------------------------------------------===//
62 // Control Flow Graph Restructuring.
65 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
66 /// predecessor is known to have one successor (BB!). Eliminate the edge
67 /// between them, moving the instructions in the predecessor into BB. This
68 /// deletes the predecessor block.
70 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB);
73 /// SimplifyCFG - This function is used to do simplification of a CFG. For
74 /// example, it adjusts branches to branches to eliminate the extra hop, it
75 /// eliminates unreachable basic blocks, and does other "peephole" optimization
76 /// of the CFG. It returns true if a modification was made, possibly deleting
77 /// the basic block that was pointed to.
79 /// WARNING: The entry node of a method may not be simplified.
81 bool SimplifyCFG(BasicBlock *BB);
83 /// DemoteRegToStack - This function takes a virtual register computed by an
84 /// Instruction and replaces it with a slot in the stack frame, allocated via
85 /// alloca. This allows the CFG to be changed around without fear of
86 /// invalidating the SSA information for the value. It returns the pointer to
87 /// the alloca inserted to create a stack slot for X.
89 AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false,
90 Instruction *AllocaPoint = 0);
92 /// DemotePHIToStack - This function takes a virtual register computed by a phi
93 /// node and replaces it with a slot in the stack frame, allocated via alloca.
94 /// The phi node is deleted and it returns the pointer to the alloca inserted.
95 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0);
97 } // End llvm namespace