include/llvm/Transforms/Utils/VNCoercion.h

   1 //===- VNCoercion.h - Value Numbering Coercion Utilities --------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 /// \file / This file provides routines used by LLVM's value numbering passes to
   9 /// perform various forms of value extraction from memory when the types are not
  10 /// identical.  For example, given
  11 ///
  12 /// store i32 8, i32 *%foo
  13 /// %a = bitcast i32 *%foo to i16
  14 /// %val = load i16, i16 *%a
  15 ///
  16 /// It possible to extract the value of the load of %a from the store to %foo.
  17 /// These routines know how to tell whether they can do that (the analyze*
  18 /// routines), and can also insert the necessary IR to do it (the get*
  19 /// routines).
  20
  21 #ifndef LLVM_TRANSFORMS_UTILS_VNCOERCION_H
  22 #define LLVM_TRANSFORMS_UTILS_VNCOERCION_H
  23 #include "llvm/IR/IRBuilder.h"
  24
  25 namespace llvm {
  26 class Function;
  27 class StoreInst;
  28 class LoadInst;
  29 class MemIntrinsic;
  30 class Instruction;
  31 class Value;
  32 class Type;
  33 class DataLayout;
  34 namespace VNCoercion {
  35 /// Return true if CoerceAvailableValueToLoadType would succeed if it was
  36 /// called.
  37 bool canCoerceMustAliasedValueToLoad(Value *StoredVal, Type *LoadTy,
  38                                      const DataLayout &DL);
  39
  40 /// If we saw a store of a value to memory, and then a load from a must-aliased
  41 /// pointer of a different type, try to coerce the stored value to the loaded
  42 /// type.  LoadedTy is the type of the load we want to replace.  IRB is
  43 /// IRBuilder used to insert new instructions.
  44 ///
  45 /// If we can't do it, return null.
  46 Value *coerceAvailableValueToLoadType(Value *StoredVal, Type *LoadedTy,
  47                                       IRBuilder<> &IRB, const DataLayout &DL);
  48
  49 /// This function determines whether a value for the pointer LoadPtr can be
  50 /// extracted from the store at DepSI.
  51 ///
  52 /// On success, it returns the offset into DepSI that extraction would start.
  53 /// On failure, it returns -1.
  54 int analyzeLoadFromClobberingStore(Type *LoadTy, Value *LoadPtr,
  55                                    StoreInst *DepSI, const DataLayout &DL);
  56
  57 /// This function determines whether a value for the pointer LoadPtr can be
  58 /// extracted from the load at DepLI.
  59 ///
  60 /// On success, it returns the offset into DepLI that extraction would start.
  61 /// On failure, it returns -1.
  62 int analyzeLoadFromClobberingLoad(Type *LoadTy, Value *LoadPtr, LoadInst *DepLI,
  63                                   const DataLayout &DL);
  64
  65 /// This function determines whether a value for the pointer LoadPtr can be
  66 /// extracted from the memory intrinsic at DepMI.
  67 ///
  68 /// On success, it returns the offset into DepMI that extraction would start.
  69 /// On failure, it returns -1.
  70 int analyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr,
  71                                      MemIntrinsic *DepMI, const DataLayout &DL);
  72
  73 /// If analyzeLoadFromClobberingStore returned an offset, this function can be
  74 /// used to actually perform the extraction of the bits from the store. It
  75 /// inserts instructions to do so at InsertPt, and returns the extracted value.
  76 Value *getStoreValueForLoad(Value *SrcVal, unsigned Offset, Type *LoadTy,
  77                             Instruction *InsertPt, const DataLayout &DL);
  78 // This is the same as getStoreValueForLoad, except it performs no insertion
  79 // It only allows constant inputs.
  80 Constant *getConstantStoreValueForLoad(Constant *SrcVal, unsigned Offset,
  81                                        Type *LoadTy, const DataLayout &DL);
  82
  83 /// If analyzeLoadFromClobberingLoad returned an offset, this function can be
  84 /// used to actually perform the extraction of the bits from the load, including
  85 /// any necessary load widening.  It inserts instructions to do so at InsertPt,
  86 /// and returns the extracted value.
  87 Value *getLoadValueForLoad(LoadInst *SrcVal, unsigned Offset, Type *LoadTy,
  88                            Instruction *InsertPt, const DataLayout &DL);
  89 // This is the same as getLoadValueForLoad, except it is given the load value as
  90 // a constant. It returns nullptr if it would require widening the load.
  91 Constant *getConstantLoadValueForLoad(Constant *SrcVal, unsigned Offset,
  92                                       Type *LoadTy, const DataLayout &DL);
  93
  94 /// If analyzeLoadFromClobberingMemInst returned an offset, this function can be
  95 /// used to actually perform the extraction of the bits from the memory
  96 /// intrinsic.  It inserts instructions to do so at InsertPt, and returns the
  97 /// extracted value.
  98 Value *getMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset,
  99                               Type *LoadTy, Instruction *InsertPt,
 100                               const DataLayout &DL);
 101 // This is the same as getStoreValueForLoad, except it performs no insertion.
 102 // It returns nullptr if it cannot produce a constant.
 103 Constant *getConstantMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset,
 104                                          Type *LoadTy, const DataLayout &DL);
 105 }
 106 }
 107 #endif