ConstantFolding.h revision 83e3c4f9d796a5da223a3ebd5d4ba985c7ecc39d 
1//===-- ConstantFolding.h - Fold instructions into constants --------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file declares routines for folding instructions into constants.
11//
12// Also, to supplement the basic VMCore ConstantExpr simplifications,
13// this file declares some additional folding routines that can make use of
14// TargetData information. These functions cannot go in VMCore due to library
15// dependency issues.
16//
17//===----------------------------------------------------------------------===//
18
19#ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H
20#define LLVM_ANALYSIS_CONSTANTFOLDING_H
21
22namespace llvm {
23  class Constant;
24  class ConstantExpr;
25  class Instruction;
26  class TargetData;
27  class Function;
28  class Type;
29  class LLVMContext;
30
31/// ConstantFoldInstruction - Attempt to constant fold the specified
32/// instruction.  If successful, the constant result is returned, if not, null
33/// is returned.  Note that this function can only fail when attempting to fold
34/// instructions like loads and stores, which have no constant expression form.
35///
36Constant *ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
37                                  const TargetData *TD = 0);
38
39/// ConstantFoldConstantExpression - Attempt to fold the constant expression
40/// using the specified TargetData.  If successful, the constant result is
41/// result is returned, if not, null is returned.
42Constant *ConstantFoldConstantExpression(ConstantExpr *CE, LLVMContext &Context,
43                                         const TargetData *TD = 0);
44
45/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
46/// specified operands.  If successful, the constant result is returned, if not,
47/// null is returned.  Note that this function can fail when attempting to
48/// fold instructions like loads and stores, which have no constant expression
49/// form.
50///
51Constant *ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
52                                   Constant*const * Ops, unsigned NumOps,
53                                   LLVMContext &Context,
54                                   const TargetData *TD = 0);
55
56/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
57/// instruction (icmp/fcmp) with the specified operands.  If it fails, it
58/// returns a constant expression of the specified operands.
59///
60Constant *ConstantFoldCompareInstOperands(unsigned Predicate,
61                                          Constant*const * Ops, unsigned NumOps,
62                                          LLVMContext &Context,
63                                          const TargetData *TD = 0);
64
65
66/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
67/// getelementptr constantexpr, return the constant value being addressed by the
68/// constant expression, or null if something is funny and we can't decide.
69Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE,
70                                                 LLVMContext &Context);
71
72/// canConstantFoldCallTo - Return true if its even possible to fold a call to
73/// the specified function.
74bool canConstantFoldCallTo(const Function *F);
75
76/// ConstantFoldCall - Attempt to constant fold a call to the specified function
77/// with the specified arguments, returning null if unsuccessful.
78Constant *
79ConstantFoldCall(Function *F, Constant* const* Operands, unsigned NumOperands);
80}
81
82#endif
83