1 //===-- Local.h - Functions to perform local transformations ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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"
25 //===----------------------------------------------------------------------===//
26 // Local constant propagation...
29 /// doConstantPropagation - Constant prop a specific instruction. Returns true
30 /// and potentially moves the iterator if constant propagation was performed.
32 bool doConstantPropagation(BasicBlock::iterator &I);
34 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
35 /// constant value, convert it into an unconditional branch to the constant
36 /// destination. This is a nontrivial operation because the successors of this
37 /// basic block must have their PHI nodes updated.
39 bool ConstantFoldTerminator(BasicBlock *BB);
41 /// ConstantFoldInstruction - Attempt to constant fold the specified
42 /// instruction. If successful, the constant result is returned, if not, null
43 /// is returned. Note that this function can only fail when attempting to fold
44 /// instructions like loads and stores, which have no constant expression form.
46 Constant *ConstantFoldInstruction(Instruction *I);
49 //===----------------------------------------------------------------------===//
50 // Local dead code elimination...
53 /// isInstructionTriviallyDead - Return true if the result produced by the
54 /// instruction is not used, and the instruction has no side effects.
56 bool isInstructionTriviallyDead(Instruction *I);
59 /// dceInstruction - Inspect the instruction at *BBI and figure out if it
60 /// isTriviallyDead. If so, remove the instruction and update the iterator to
61 /// point to the instruction that immediately succeeded the original
64 bool dceInstruction(BasicBlock::iterator &BBI);
66 //===----------------------------------------------------------------------===//
67 // PHI Instruction Simplification
70 /// hasConstantValue - If the specified PHI node always merges together the same
71 /// value, return the value, otherwise return null.
73 Value *hasConstantValue(PHINode *PN);
76 //===----------------------------------------------------------------------===//
77 // Control Flow Graph Restructuring...
80 /// SimplifyCFG - This function is used to do simplification of a CFG. For
81 /// example, it adjusts branches to branches to eliminate the extra hop, it
82 /// eliminates unreachable basic blocks, and does other "peephole" optimization
83 /// of the CFG. It returns true if a modification was made, possibly deleting
84 /// the basic block that was pointed to.
86 /// WARNING: The entry node of a method may not be simplified.
88 bool SimplifyCFG(BasicBlock *BB);
90 } // End llvm namespace