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 struct DbgInfoIntrinsic;
31 template<typename T> class SmallVectorImpl;
33 //===----------------------------------------------------------------------===//
34 // Local constant propagation.
37 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
38 /// constant value, convert it into an unconditional branch to the constant
39 /// destination. This is a nontrivial operation because the successors of this
40 /// basic block must have their PHI nodes updated.
42 bool ConstantFoldTerminator(BasicBlock *BB);
44 //===----------------------------------------------------------------------===//
45 // Local dead code elimination.
48 /// isInstructionTriviallyDead - Return true if the result produced by the
49 /// instruction is not used, and the instruction has no side effects.
51 bool isInstructionTriviallyDead(Instruction *I);
54 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
55 /// trivially dead instruction, delete it. If that makes any of its operands
56 /// trivially dead, delete them too, recursively.
58 /// If DeadInst is specified, the vector is filled with the instructions that
59 /// are actually deleted.
60 void RecursivelyDeleteTriviallyDeadInstructions(Value *V,
61 SmallVectorImpl<Instruction*> *DeadInst = 0);
63 //===----------------------------------------------------------------------===//
64 // Control Flow Graph Restructuring.
67 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
68 /// predecessor is known to have one successor (BB!). Eliminate the edge
69 /// between them, moving the instructions in the predecessor into BB. This
70 /// deletes the predecessor block.
72 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB);
75 /// SimplifyCFG - This function is used to do simplification of a CFG. For
76 /// example, it adjusts branches to branches to eliminate the extra hop, it
77 /// eliminates unreachable basic blocks, and does other "peephole" optimization
78 /// of the CFG. It returns true if a modification was made, possibly deleting
79 /// the basic block that was pointed to.
81 /// WARNING: The entry node of a method may not be simplified.
83 bool SimplifyCFG(BasicBlock *BB);
85 /// DemoteRegToStack - This function takes a virtual register computed by an
86 /// Instruction and replaces it with a slot in the stack frame, allocated via
87 /// alloca. This allows the CFG to be changed around without fear of
88 /// invalidating the SSA information for the value. It returns the pointer to
89 /// the alloca inserted to create a stack slot for X.
91 AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false,
92 Instruction *AllocaPoint = 0);
94 /// DemotePHIToStack - This function takes a virtual register computed by a phi
95 /// node and replaces it with a slot in the stack frame, allocated via alloca.
96 /// The phi node is deleted and it returns the pointer to the alloca inserted.
97 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0);
99 /// OnlyUsedByDbgIntrinsics - Return true if the instruction I is only used
100 /// by DbgIntrinsics. If DbgInUses is specified then the vector is filled
101 /// with DbgInfoIntrinsic that use the instruction I.
102 bool OnlyUsedByDbgInfoIntrinsics(Instruction *I,
103 SmallVectorImpl<DbgInfoIntrinsic *> *DbgInUses = 0);
105 /// UserIsDebugInfo - Return true if U is a constant expr used by
106 /// llvm.dbg.variable or llvm.dbg.global_variable
107 bool UserIsDebugInfo(User *U);
109 /// RemoveDbgInfoUser - Remove an User which is representing debug info.
110 void RemoveDbgInfoUser(User *U);
112 } // End llvm namespace