ConstantFolding.h revision 878e4946700824954d7eb7f3ff660353db8e0d17 
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/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
66/// produce if it is constant and determinable.  If this is not determinable,
67/// return null.
68Constant *ConstantFoldLoadFromConstPtr(Constant *C, const TargetData *TD = 0);
69
70/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
71/// getelementptr constantexpr, return the constant value being addressed by the
72/// constant expression, or null if something is funny and we can't decide.
73Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE);
74
75/// canConstantFoldCallTo - Return true if its even possible to fold a call to
76/// the specified function.
77bool canConstantFoldCallTo(const Function *F);
78
79/// ConstantFoldCall - Attempt to constant fold a call to the specified function
80/// with the specified arguments, returning null if unsuccessful.
81Constant *
82ConstantFoldCall(Function *F, Constant* const* Operands, unsigned NumOperands);
83}
84
85#endif
86