ConstantFolding.h revision dabc2806726a286b00313419fac8461ebe0f774c
1f2ba7591b1407a7ee9209f842c50696914dc2dedkbr@chromium.org//===-- ConstantFolding.h - Fold instructions into constants --------------===// 2f2ba7591b1407a7ee9209f842c50696914dc2dedkbr@chromium.org// 3f2ba7591b1407a7ee9209f842c50696914dc2dedkbr@chromium.org// 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 template<typename T> 31 class ArrayRef; 32 33/// ConstantFoldInstruction - Try to constant fold the specified instruction. 34/// If successful, the constant result is returned, if not, null is returned. 35/// Note that this fails if not all of the operands are constant. Otherwise, 36/// this function can only fail when attempting to fold instructions like loads 37/// and stores, which have no constant expression form. 38Constant *ConstantFoldInstruction(Instruction *I, const TargetData *TD = 0); 39 40/// ConstantFoldConstantExpression - Attempt to fold the constant expression 41/// using the specified TargetData. If successful, the constant result is 42/// result is returned, if not, null is returned. 43Constant *ConstantFoldConstantExpression(const ConstantExpr *CE, 44 const TargetData *TD = 0); 45 46/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the 47/// specified operands. If successful, the constant result is returned, if not, 48/// null is returned. Note that this function can fail when attempting to 49/// fold instructions like loads and stores, which have no constant expression 50/// form. 51/// 52Constant *ConstantFoldInstOperands(unsigned Opcode, Type *DestTy, 53 ArrayRef<Constant *> Ops, 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 *LHS, Constant *RHS, 62 const TargetData *TD = 0); 63 64/// ConstantFoldInsertValueInstruction - Attempt to constant fold an insertvalue 65/// instruction with the specified operands and indices. The constant result is 66/// returned if successful; if not, null is returned. 67Constant *ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val, 68 ArrayRef<unsigned> Idxs); 69 70/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would 71/// produce if it is constant and determinable. If this is not determinable, 72/// return null. 73Constant *ConstantFoldLoadFromConstPtr(Constant *C, const TargetData *TD = 0); 74 75/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a 76/// getelementptr constantexpr, return the constant value being addressed by the 77/// constant expression, or null if something is funny and we can't decide. 78Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE); 79 80/// canConstantFoldCallTo - Return true if its even possible to fold a call to 81/// the specified function. 82bool canConstantFoldCallTo(const Function *F); 83 84/// ConstantFoldCall - Attempt to constant fold a call to the specified function 85/// with the specified arguments, returning null if unsuccessful. 86Constant * 87ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands); 88} 89 90#endif 91