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"
19 #include "llvm/Analysis/ConstantFolding.h"
28 //===----------------------------------------------------------------------===//
29 // Local constant propagation...
32 /// doConstantPropagation - Constant prop a specific instruction. Returns true
33 /// and potentially moves the iterator if constant propagation was performed.
35 bool doConstantPropagation(BasicBlock::iterator &I);
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 /// ConstantFoldInstruction - Attempt to constant fold the specified
45 /// instruction. If successful, the constant result is returned, if not, null
46 /// is returned. Note that this function can only fail when attempting to fold
47 /// instructions like loads and stores, which have no constant expression form.
49 Constant *ConstantFoldInstruction(Instruction *I);
51 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
52 /// specified operands. If successful, the constant result is returned, if not,
53 /// null is returned. Note that this function can fail when attempting to
54 /// fold instructions like loads and stores, which have no constant expression
57 Constant *ConstantFoldInstOperands(
58 const Instruction *I, ///< The model instruction
59 const std::vector<Constant*> &Ops ///< The constant operands to use.
63 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
64 /// getelementptr constantexpr, return the constant value being addressed by the
65 /// constant expression, or null if something is funny and we can't decide.
66 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE);
68 //===----------------------------------------------------------------------===//
69 // Local dead code elimination...
72 /// isInstructionTriviallyDead - Return true if the result produced by the
73 /// instruction is not used, and the instruction has no side effects.
75 bool isInstructionTriviallyDead(Instruction *I);
78 /// dceInstruction - Inspect the instruction at *BBI and figure out if it
79 /// isTriviallyDead. If so, remove the instruction and update the iterator to
80 /// point to the instruction that immediately succeeded the original
83 bool dceInstruction(BasicBlock::iterator &BBI);
85 //===----------------------------------------------------------------------===//
86 // Control Flow Graph Restructuring...
89 /// SimplifyCFG - This function is used to do simplification of a CFG. For
90 /// example, it adjusts branches to branches to eliminate the extra hop, it
91 /// eliminates unreachable basic blocks, and does other "peephole" optimization
92 /// of the CFG. It returns true if a modification was made, possibly deleting
93 /// the basic block that was pointed to.
95 /// WARNING: The entry node of a method may not be simplified.
97 bool SimplifyCFG(BasicBlock *BB);
99 /// DemoteRegToStack - This function takes a virtual register computed by an
100 /// Instruction and replaces it with a slot in the stack frame, allocated via
101 /// alloca. This allows the CFG to be changed around without fear of
102 /// invalidating the SSA information for the value. It returns the pointer to
103 /// the alloca inserted to create a stack slot for X.
105 AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false);
107 } // End llvm namespace