ConstantFolding.h revision db125cfaf57cc83e7dd7453de2d509bc8efd0e5e
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 when all 11// operands are constants, for example "sub i32 1, 0" -> "1". 12// 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 16// dependency issues. 17// 18//===----------------------------------------------------------------------===// 19 20#ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H 21#define LLVM_ANALYSIS_CONSTANTFOLDING_H 22 23namespace llvm { 24 class Constant; 25 class ConstantExpr; 26 class Instruction; 27 class TargetData; 28 class Function; 29 class Type; 30 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. 36Constant *ConstantFoldInstruction(Instruction *I, const TargetData *TD = 0); 37 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. 41Constant *ConstantFoldConstantExpression(const ConstantExpr *CE, 42 const TargetData *TD = 0); 43 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 48/// form. 49/// 50Constant *ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 51 Constant *const *Ops, unsigned NumOps, 52 const TargetData *TD = 0); 53 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. 57/// 58Constant *ConstantFoldCompareInstOperands(unsigned Predicate, 59 Constant *LHS, Constant *RHS, 60 const TargetData *TD = 0); 61 62/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 63/// produce if it is constant and determinable. If this is not determinable, 64/// return null. 65Constant *ConstantFoldLoadFromConstPtr(Constant *C, const TargetData *TD = 0); 66 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. 70Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE); 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