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
18 #include "llvm/Function.h"
28 //===----------------------------------------------------------------------===//
29 // Local constant propagation.
32 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
33 /// constant value, convert it into an unconditional branch to the constant
34 /// destination. This is a nontrivial operation because the successors of this
35 /// basic block must have their PHI nodes updated.
37 bool ConstantFoldTerminator(BasicBlock *BB);
39 //===----------------------------------------------------------------------===//
40 // Local dead code elimination.
43 /// isInstructionTriviallyDead - Return true if the result produced by the
44 /// instruction is not used, and the instruction has no side effects.
46 bool isInstructionTriviallyDead(Instruction *I);
49 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
50 /// trivially dead instruction, delete it. If that makes any of its operands
51 /// trivially dead, delete them too, recursively.
53 /// If DeadInst is specified, the vector is filled with the instructions that
54 /// are actually deleted.
55 void RecursivelyDeleteTriviallyDeadInstructions(Value *V,
56 SmallVectorImpl<Instruction*> *DeadInst = 0);
58 //===----------------------------------------------------------------------===//
59 // Control Flow Graph Restructuring...
62 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
63 /// predecessor is known to have one successor (BB!). Eliminate the edge
64 /// between them, moving the instructions in the predecessor into BB. This
65 /// deletes the predecessor block.
67 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB);
70 /// SimplifyCFG - This function is used to do simplification of a CFG. For
71 /// example, it adjusts branches to branches to eliminate the extra hop, it
72 /// eliminates unreachable basic blocks, and does other "peephole" optimization
73 /// of the CFG. It returns true if a modification was made, possibly deleting
74 /// the basic block that was pointed to.
76 /// WARNING: The entry node of a method may not be simplified.
78 bool SimplifyCFG(BasicBlock *BB);
80 /// DemoteRegToStack - This function takes a virtual register computed by an
81 /// Instruction and replaces it with a slot in the stack frame, allocated via
82 /// alloca. This allows the CFG to be changed around without fear of
83 /// invalidating the SSA information for the value. It returns the pointer to
84 /// the alloca inserted to create a stack slot for X.
86 AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false,
87 Instruction *AllocaPoint = NULL);
89 /// DemotePHIToStack - This function takes a virtual register computed by a phi
90 /// node and replaces it with a slot in the stack frame, allocated via alloca.
91 /// The phi node is deleted and it returns the pointer to the alloca inserted.
92 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = NULL);
94 } // End llvm namespace