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);
52 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
53 /// getelementptr constantexpr, return the constant value being addressed by the
54 /// constant expression, or null if something is funny and we can't decide.
55 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE);
57 //===----------------------------------------------------------------------===//
58 // Local dead code elimination...
61 /// isInstructionTriviallyDead - Return true if the result produced by the
62 /// instruction is not used, and the instruction has no side effects.
64 bool isInstructionTriviallyDead(Instruction *I);
67 /// dceInstruction - Inspect the instruction at *BBI and figure out if it
68 /// isTriviallyDead. If so, remove the instruction and update the iterator to
69 /// point to the instruction that immediately succeeded the original
72 bool dceInstruction(BasicBlock::iterator &BBI);
74 //===----------------------------------------------------------------------===//
75 // Control Flow Graph Restructuring...
78 /// SimplifyCFG - This function is used to do simplification of a CFG. For
79 /// example, it adjusts branches to branches to eliminate the extra hop, it
80 /// eliminates unreachable basic blocks, and does other "peephole" optimization
81 /// of the CFG. It returns true if a modification was made, possibly deleting
82 /// the basic block that was pointed to.
84 /// WARNING: The entry node of a method may not be simplified.
86 bool SimplifyCFG(BasicBlock *BB);
88 /// DemoteRegToStack - This function takes a virtual register computed by an
89 /// Instruction and replaces it with a slot in the stack frame, allocated via
90 /// alloca. This allows the CFG to be changed around without fear of
91 /// invalidating the SSA information for the value. It returns the pointer to
92 /// the alloca inserted to create a stack slot for X.
94 AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false);
96 } // End llvm namespace