ConstantFolding.h revision 48b2f3e4850cd27d54224cd42da8a160d6b95984 
1//===-- ConstantFolding.h - Analyze constant folding possibilities --------===//
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 family of functions determines the possibility of performing constant
11// folding.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H
16#define LLVM_ANALYSIS_CONSTANTFOLDING_H
17
18namespace llvm {
19  class Constant;
20  class ConstantExpr;
21  class Instruction;
22  class TargetData;
23  class Function;
24  class Type;
25  struct LLVMContext;
26
27/// ConstantFoldInstruction - Attempt to constant fold the specified
28/// instruction.  If successful, the constant result is returned, if not, null
29/// is returned.  Note that this function can only fail when attempting to fold
30/// instructions like loads and stores, which have no constant expression form.
31///
32Constant *ConstantFoldInstruction(Instruction *I, LLVMContext &Context,
33                                  const TargetData *TD = 0);
34
35/// ConstantFoldConstantExpression - Attempt to fold the constant expression
36/// using the specified TargetData.  If successful, the constant result is
37/// result is returned, if not, null is returned.
38Constant *ConstantFoldConstantExpression(ConstantExpr *CE, LLVMContext &Context,
39                                         const TargetData *TD = 0);
40
41/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
42/// specified operands.  If successful, the constant result is returned, if not,
43/// null is returned.  Note that this function can fail when attempting to
44/// fold instructions like loads and stores, which have no constant expression
45/// form.
46///
47Constant *ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
48                                   Constant*const * Ops, unsigned NumOps,
49                                   LLVMContext &Context,
50                                   const TargetData *TD = 0);
51
52/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
53/// instruction (icmp/fcmp) with the specified operands.  If it fails, it
54/// returns a constant expression of the specified operands.
55///
56Constant *ConstantFoldCompareInstOperands(unsigned Predicate,
57                                          Constant*const * Ops, unsigned NumOps,
58                                          LLVMContext &Context,
59                                          const TargetData *TD = 0);
60
61
62/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
63/// getelementptr constantexpr, return the constant value being addressed by the
64/// constant expression, or null if something is funny and we can't decide.
65Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE,
66                                                 LLVMContext &Context);
67
68/// canConstantFoldCallTo - Return true if its even possible to fold a call to
69/// the specified function.
70bool canConstantFoldCallTo(const Function *F);
71
72/// ConstantFoldCall - Attempt to constant fold a call to the specified function
73/// with the specified arguments, returning null if unsuccessful.
74Constant *
75ConstantFoldCall(Function *F, Constant* const* Operands, unsigned NumOperands);
76}
77
78#endif
79