1 //===-- ConstantFolding.h - Fold instructions into constants --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares routines for folding instructions into constants when all
11 // operands are constants, for example "sub i32 1, 0" -> "1".
13 // Also, to supplement the basic VMCore ConstantExpr simplifications,
14 // this file declares some additional folding routines that can make use of
15 // TargetData information. These functions cannot go in VMCore due to library
18 //===----------------------------------------------------------------------===//
20 #ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H
21 #define LLVM_ANALYSIS_CONSTANTFOLDING_H
31 /// ConstantFoldInstruction - Try to constant fold the specified instruction.
32 /// If successful, the constant result is returned, if not, null is returned.
33 /// Note that this fails if not all of the operands are constant. Otherwise,
34 /// this function can only fail when attempting to fold instructions like loads
35 /// and stores, which have no constant expression form.
36 Constant *ConstantFoldInstruction(Instruction *I, const TargetData *TD = 0);
38 /// ConstantFoldConstantExpression - Attempt to fold the constant expression
39 /// using the specified TargetData. If successful, the constant result is
40 /// result is returned, if not, null is returned.
41 Constant *ConstantFoldConstantExpression(const ConstantExpr *CE,
42 const TargetData *TD = 0);
44 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
45 /// specified operands. If successful, the constant result is returned, if not,
46 /// null is returned. Note that this function can fail when attempting to
47 /// fold instructions like loads and stores, which have no constant expression
50 Constant *ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
51 Constant *const *Ops, unsigned NumOps,
52 const TargetData *TD = 0);
54 /// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
55 /// instruction (icmp/fcmp) with the specified operands. If it fails, it
56 /// returns a constant expression of the specified operands.
58 Constant *ConstantFoldCompareInstOperands(unsigned Predicate,
59 Constant *LHS, Constant *RHS,
60 const TargetData *TD = 0);
62 /// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
63 /// produce if it is constant and determinable. If this is not determinable,
65 Constant *ConstantFoldLoadFromConstPtr(Constant *C, const TargetData *TD = 0);
67 /// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
68 /// getelementptr constantexpr, return the constant value being addressed by the
69 /// constant expression, or null if something is funny and we can't decide.
70 Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE);
72 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
73 /// the specified function.
74 bool canConstantFoldCallTo(const Function *F);
76 /// ConstantFoldCall - Attempt to constant fold a call to the specified function
77 /// with the specified arguments, returning null if unsuccessful.
79 ConstantFoldCall(Function *F, Constant *const *Operands, unsigned NumOperands);