170 lines
8.2 KiB
C
170 lines
8.2 KiB
C
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//===-- ConstantFolding.h - Fold instructions into constants ----*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares routines for folding instructions into constants when all
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// operands are constants, for example "sub i32 1, 0" -> "1".
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//
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// Also, to supplement the basic VMCore ConstantExpr simplifications,
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// this file declares some additional folding routines that can make use of
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// DataLayout information. These functions cannot go in VMCore due to library
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// dependency issues.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_CONSTANTFOLDING_H
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#define LLVM_ANALYSIS_CONSTANTFOLDING_H
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namespace llvm {
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class APInt;
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template <typename T> class ArrayRef;
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class CallBase;
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class Constant;
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class ConstantExpr;
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class DSOLocalEquivalent;
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class DataLayout;
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class Function;
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class GlobalValue;
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class Instruction;
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class TargetLibraryInfo;
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class Type;
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/// If this constant is a constant offset from a global, return the global and
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/// the constant. Because of constantexprs, this function is recursive.
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/// If the global is part of a dso_local_equivalent constant, return it through
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/// `Equiv` if it is provided.
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bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, APInt &Offset,
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const DataLayout &DL,
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DSOLocalEquivalent **DSOEquiv = nullptr);
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/// ConstantFoldInstruction - Try to constant fold the specified instruction.
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/// If successful, the constant result is returned, if not, null is returned.
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/// Note that this fails if not all of the operands are constant. Otherwise,
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/// this function can only fail when attempting to fold instructions like loads
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/// and stores, which have no constant expression form.
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Constant *ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
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const TargetLibraryInfo *TLI = nullptr);
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/// ConstantFoldConstant - Fold the constant using the specified DataLayout.
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/// This function always returns a non-null constant: Either the folding result,
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/// or the original constant if further folding is not possible.
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Constant *ConstantFoldConstant(const Constant *C, const DataLayout &DL,
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const TargetLibraryInfo *TLI = nullptr);
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/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
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/// specified operands. If successful, the constant result is returned, if not,
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/// null is returned. Note that this function can fail when attempting to
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/// fold instructions like loads and stores, which have no constant expression
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/// form.
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///
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Constant *ConstantFoldInstOperands(Instruction *I, ArrayRef<Constant *> Ops,
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const DataLayout &DL,
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const TargetLibraryInfo *TLI = nullptr);
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/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
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/// instruction (icmp/fcmp) with the specified operands. If it fails, it
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/// returns a constant expression of the specified operands.
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///
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Constant *
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ConstantFoldCompareInstOperands(unsigned Predicate, Constant *LHS,
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Constant *RHS, const DataLayout &DL,
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const TargetLibraryInfo *TLI = nullptr);
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/// Attempt to constant fold a unary operation with the specified
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/// operand. If it fails, it returns a constant expression of the specified
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/// operands.
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Constant *ConstantFoldUnaryOpOperand(unsigned Opcode, Constant *Op,
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const DataLayout &DL);
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/// Attempt to constant fold a binary operation with the specified
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/// operands. If it fails, it returns a constant expression of the specified
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/// operands.
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Constant *ConstantFoldBinaryOpOperands(unsigned Opcode, Constant *LHS,
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Constant *RHS, const DataLayout &DL);
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/// Attempt to constant fold a select instruction with the specified
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/// operands. The constant result is returned if successful; if not, null is
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/// returned.
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Constant *ConstantFoldSelectInstruction(Constant *Cond, Constant *V1,
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Constant *V2);
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/// Attempt to constant fold a cast with the specified operand. If it
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/// fails, it returns a constant expression of the specified operand.
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Constant *ConstantFoldCastOperand(unsigned Opcode, Constant *C, Type *DestTy,
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const DataLayout &DL);
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/// ConstantFoldInsertValueInstruction - Attempt to constant fold an insertvalue
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/// instruction with the specified operands and indices. The constant result is
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/// returned if successful; if not, null is returned.
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Constant *ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val,
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ArrayRef<unsigned> Idxs);
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/// Attempt to constant fold an extractvalue instruction with the
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/// specified operands and indices. The constant result is returned if
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/// successful; if not, null is returned.
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Constant *ConstantFoldExtractValueInstruction(Constant *Agg,
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ArrayRef<unsigned> Idxs);
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/// Attempt to constant fold an insertelement instruction with the
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/// specified operands and indices. The constant result is returned if
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/// successful; if not, null is returned.
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Constant *ConstantFoldInsertElementInstruction(Constant *Val,
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Constant *Elt,
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Constant *Idx);
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/// Attempt to constant fold an extractelement instruction with the
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/// specified operands and indices. The constant result is returned if
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/// successful; if not, null is returned.
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Constant *ConstantFoldExtractElementInstruction(Constant *Val, Constant *Idx);
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/// Attempt to constant fold a shufflevector instruction with the
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/// specified operands and mask. See class ShuffleVectorInst for a description
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/// of the mask representation. The constant result is returned if successful;
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/// if not, null is returned.
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Constant *ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2,
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ArrayRef<int> Mask);
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/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
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/// produce if it is constant and determinable. If this is not determinable,
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/// return null.
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Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, const DataLayout &DL);
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/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
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/// getelementptr constantexpr, return the constant value being addressed by the
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/// constant expression, or null if something is funny and we can't decide.
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Constant *ConstantFoldLoadThroughGEPConstantExpr(Constant *C, ConstantExpr *CE);
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/// ConstantFoldLoadThroughGEPIndices - Given a constant and getelementptr
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/// indices (with an *implied* zero pointer index that is not in the list),
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/// return the constant value being addressed by a virtual load, or null if
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/// something is funny and we can't decide.
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Constant *ConstantFoldLoadThroughGEPIndices(Constant *C,
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ArrayRef<Constant *> Indices);
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/// canConstantFoldCallTo - Return true if its even possible to fold a call to
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/// the specified function.
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bool canConstantFoldCallTo(const CallBase *Call, const Function *F);
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/// ConstantFoldCall - Attempt to constant fold a call to the specified function
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/// with the specified arguments, returning null if unsuccessful.
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Constant *ConstantFoldCall(const CallBase *Call, Function *F,
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ArrayRef<Constant *> Operands,
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const TargetLibraryInfo *TLI = nullptr);
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/// ConstantFoldLoadThroughBitcast - try to cast constant to destination type
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/// returning null if unsuccessful. Can cast pointer to pointer or pointer to
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/// integer and vice versa if their sizes are equal.
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Constant *ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy,
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const DataLayout &DL);
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/// Check whether the given call has no side-effects.
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/// Specifically checks for math routimes which sometimes set errno.
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bool isMathLibCallNoop(const CallBase *Call, const TargetLibraryInfo *TLI);
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}
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#endif
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