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 //===----------------------------------------------------------------------===//
37 /// isSafeToLoadUnconditionally - Return true if we know that executing a load
38 /// from this value cannot trap. If it is not obviously safe to load from the
39 /// specified pointer, we do a quick local scan of the basic block containing
40 /// ScanFrom, to determine if the address is already accessed.
41 bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom);
43 //===----------------------------------------------------------------------===//
44 // Local constant propagation.
47 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
48 /// constant value, convert it into an unconditional branch to the constant
49 /// destination. This is a nontrivial operation because the successors of this
50 /// basic block must have their PHI nodes updated.
52 bool ConstantFoldTerminator(BasicBlock *BB);
54 //===----------------------------------------------------------------------===//
55 // Local dead code elimination.
58 /// isInstructionTriviallyDead - Return true if the result produced by the
59 /// instruction is not used, and the instruction has no side effects.
61 bool isInstructionTriviallyDead(Instruction *I);
63 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
64 /// trivially dead instruction, delete it. If that makes any of its operands
65 /// trivially dead, delete them too, recursively.
66 void RecursivelyDeleteTriviallyDeadInstructions(Value *V);
68 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
69 /// dead PHI node, due to being a def-use chain of single-use nodes that
70 /// either forms a cycle or is terminated by a trivially dead instruction,
71 /// delete it. If that makes any of its operands trivially dead, delete them
73 void RecursivelyDeleteDeadPHINode(PHINode *PN);
75 //===----------------------------------------------------------------------===//
76 // Control Flow Graph Restructuring.
79 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
80 /// predecessor is known to have one successor (BB!). Eliminate the edge
81 /// between them, moving the instructions in the predecessor into BB. This
82 /// deletes the predecessor block.
84 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB);
87 /// SimplifyCFG - This function is used to do simplification of a CFG. For
88 /// example, it adjusts branches to branches to eliminate the extra hop, it
89 /// eliminates unreachable basic blocks, and does other "peephole" optimization
90 /// of the CFG. It returns true if a modification was made, possibly deleting
91 /// the basic block that was pointed to.
93 /// WARNING: The entry node of a method may not be simplified.
95 bool SimplifyCFG(BasicBlock *BB);
97 /// DemoteRegToStack - This function takes a virtual register computed by an
98 /// Instruction and replaces it with a slot in the stack frame, allocated via
99 /// alloca. This allows the CFG to be changed around without fear of
100 /// invalidating the SSA information for the value. It returns the pointer to
101 /// the alloca inserted to create a stack slot for X.
103 AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false,
104 Instruction *AllocaPoint = 0);
106 /// DemotePHIToStack - This function takes a virtual register computed by a phi
107 /// node and replaces it with a slot in the stack frame, allocated via alloca.
108 /// The phi node is deleted and it returns the pointer to the alloca inserted.
109 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0);
111 /// OnlyUsedByDbgIntrinsics - Return true if the instruction I is only used
112 /// by DbgIntrinsics. If DbgInUses is specified then the vector is filled
113 /// with DbgInfoIntrinsic that use the instruction I.
114 bool OnlyUsedByDbgInfoIntrinsics(Instruction *I,
115 SmallVectorImpl<DbgInfoIntrinsic *> *DbgInUses = 0);
117 /// UserIsDebugInfo - Return true if U is a constant expr used by
118 /// llvm.dbg.variable or llvm.dbg.global_variable
119 bool UserIsDebugInfo(User *U);
121 /// RemoveDbgInfoUser - Remove an User which is representing debug info.
122 void RemoveDbgInfoUser(User *U);
124 } // End llvm namespace