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"
26 //===----------------------------------------------------------------------===//
27 // Local constant propagation...
30 /// doConstantPropagation - Constant prop a specific instruction. Returns true
31 /// and potentially moves the iterator if constant propagation was performed.
33 bool doConstantPropagation(BasicBlock::iterator &I);
35 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
36 /// constant value, convert it into an unconditional branch to the constant
37 /// destination. This is a nontrivial operation because the successors of this
38 /// basic block must have their PHI nodes updated.
40 bool ConstantFoldTerminator(BasicBlock *BB);
42 /// ConstantFoldInstruction - Attempt to constant fold the specified
43 /// instruction. If successful, the constant result is returned, if not, null
44 /// is returned. Note that this function can only fail when attempting to fold
45 /// instructions like loads and stores, which have no constant expression form.
47 Constant *ConstantFoldInstruction(Instruction *I);
50 //===----------------------------------------------------------------------===//
51 // Local dead code elimination...
54 /// isInstructionTriviallyDead - Return true if the result produced by the
55 /// instruction is not used, and the instruction has no side effects.
57 bool isInstructionTriviallyDead(Instruction *I);
60 /// dceInstruction - Inspect the instruction at *BBI and figure out if it
61 /// isTriviallyDead. If so, remove the instruction and update the iterator to
62 /// point to the instruction that immediately succeeded the original
65 bool dceInstruction(BasicBlock::iterator &BBI);
67 //===----------------------------------------------------------------------===//
68 // PHI Instruction Simplification
71 /// hasConstantValue - If the specified PHI node always merges together the same
72 /// value, return the value, otherwise return null.
74 Value *hasConstantValue(PHINode *PN);
77 //===----------------------------------------------------------------------===//
78 // Control Flow Graph Restructuring...
81 /// SimplifyCFG - This function is used to do simplification of a CFG. For
82 /// example, it adjusts branches to branches to eliminate the extra hop, it
83 /// eliminates unreachable basic blocks, and does other "peephole" optimization
84 /// of the CFG. It returns true if a modification was made, possibly deleting
85 /// the basic block that was pointed to.
87 /// WARNING: The entry node of a method may not be simplified.
89 bool SimplifyCFG(BasicBlock *BB);
91 /// DemoteRegToStack - This function takes a virtual register computed by an
92 /// Instruction& X and replaces it with a slot in the stack frame, allocated via
93 /// alloca. This allows the CFG to be changed around without fear of
94 /// invalidating the SSA information for the value. It returns the pointer to
95 /// the alloca inserted to create a stack slot for X.
97 AllocaInst *DemoteRegToStack(Instruction &X);
99 } // End llvm namespace