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
28 struct DbgInfoIntrinsic;
30 template<typename T> class SmallVectorImpl;
32 //===----------------------------------------------------------------------===//
33 // Local constant propagation.
36 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
37 /// constant value, convert it into an unconditional branch to the constant
38 /// destination. This is a nontrivial operation because the successors of this
39 /// basic block must have their PHI nodes updated.
41 bool ConstantFoldTerminator(BasicBlock *BB);
43 //===----------------------------------------------------------------------===//
44 // Local dead code elimination.
47 /// isInstructionTriviallyDead - Return true if the result produced by the
48 /// instruction is not used, and the instruction has no side effects.
50 bool isInstructionTriviallyDead(Instruction *I);
53 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
54 /// trivially dead instruction, delete it. If that makes any of its operands
55 /// trivially dead, delete them too, recursively.
57 /// If DeadInst is specified, the vector is filled with the instructions that
58 /// are actually deleted.
59 void RecursivelyDeleteTriviallyDeadInstructions(Value *V,
60 SmallVectorImpl<Instruction*> *DeadInst = 0);
62 //===----------------------------------------------------------------------===//
63 // Control Flow Graph Restructuring.
66 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
67 /// predecessor is known to have one successor (BB!). Eliminate the edge
68 /// between them, moving the instructions in the predecessor into BB. This
69 /// deletes the predecessor block.
71 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB);
74 /// SimplifyCFG - This function is used to do simplification of a CFG. For
75 /// example, it adjusts branches to branches to eliminate the extra hop, it
76 /// eliminates unreachable basic blocks, and does other "peephole" optimization
77 /// of the CFG. It returns true if a modification was made, possibly deleting
78 /// the basic block that was pointed to.
80 /// WARNING: The entry node of a method may not be simplified.
82 bool SimplifyCFG(BasicBlock *BB);
84 /// DemoteRegToStack - This function takes a virtual register computed by an
85 /// Instruction and replaces it with a slot in the stack frame, allocated via
86 /// alloca. This allows the CFG to be changed around without fear of
87 /// invalidating the SSA information for the value. It returns the pointer to
88 /// the alloca inserted to create a stack slot for X.
90 AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false,
91 Instruction *AllocaPoint = 0);
93 /// DemotePHIToStack - This function takes a virtual register computed by a phi
94 /// node and replaces it with a slot in the stack frame, allocated via alloca.
95 /// The phi node is deleted and it returns the pointer to the alloca inserted.
96 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0);
98 /// OnlyUsedByDbgIntrinsics - Return true if the instruction I is only used
99 /// by DbgIntrinsics. If DbgInUses is specified then the vector is filled
100 /// with DbgInfoIntrinsic that use the instruction I.
101 bool OnlyUsedByDbgInfoIntrinsics(Instruction *I,
102 SmallVectorImpl<DbgInfoIntrinsic *> *DbgInUses = 0);
103 } // End llvm namespace