1173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner//===- llvm/Analysis/ValueTracking.h - Walk computations --------*- C++ -*-===// 2173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 3173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// The LLVM Compiler Infrastructure 4173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 5173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// This file is distributed under the University of Illinois Open Source 6173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// License. See LICENSE.TXT for details. 7173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 8173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner//===----------------------------------------------------------------------===// 9173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 10173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// This file contains routines that help analyze properties that chains of 11173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// computations have. 12173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner// 13173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner//===----------------------------------------------------------------------===// 14173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 15173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#ifndef LLVM_ANALYSIS_VALUETRACKING_H 16173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#define LLVM_ANALYSIS_VALUETRACKING_H 17173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 18fc6d3a49867cd38954dc40936a88f1907252c6d2Jay Foad#include "llvm/ADT/ArrayRef.h" 191f6efa3996dd1929fbc129203ce5009b620e6969Michael J. Spencer#include "llvm/Support/DataTypes.h" 200d2b0aba424bd3959bb5c807873def8f53e57a3cEric Christopher 21173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattnernamespace llvm { 22173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner class Value; 23b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman class Instruction; 24173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner class APInt; 253574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow class DataLayout; 2618c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner class StringRef; 2795d594cac3737ae1594a391276942a443cac426bRafael Espindola class MDNode; 2895d594cac3737ae1594a391276942a443cac426bRafael Espindola 29173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// ComputeMaskedBits - Determine which of the bits specified in Mask are 30173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// known to be either zero or one and return them in the KnownZero/KnownOne 31173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// bit sets. This code only analyzes bits in Mask, in order to short-circuit 32173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// processing. 33cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// 34cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// This function is defined on values with integer type, values with pointer 35cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// type (but only if TD is non-null), and vectors of integers. In the case 36cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// where V is a vector, the mask, known zero, and known one values are the 37cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// same width as the vector element, and the bit is set only if it is true 38cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// for all of the elements in the vector. 3926c8dcc692fb2addd475446cfff24d6a4e958bcaRafael Espindola void ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne, 403574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow const DataLayout *TD = 0, unsigned Depth = 0); 4126c8dcc692fb2addd475446cfff24d6a4e958bcaRafael Espindola void computeMaskedBitsLoad(const MDNode &Ranges, APInt &KnownZero); 4295d594cac3737ae1594a391276942a443cac426bRafael Espindola 43d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands /// ComputeSignBit - Determine whether the sign bit is known to be zero or 44d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands /// one. Convenience wrapper around ComputeMaskedBits. 45d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands void ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne, 463574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow const DataLayout *TD = 0, unsigned Depth = 0); 47d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands 48dbaa2376f7b3c027e895ff4bee3ae08351f3ea88Rafael Espindola /// isKnownToBeAPowerOfTwo - Return true if the given value is known to have 49dbaa2376f7b3c027e895ff4bee3ae08351f3ea88Rafael Espindola /// exactly one bit set when defined. For vectors return true if every 50dbaa2376f7b3c027e895ff4bee3ae08351f3ea88Rafael Espindola /// element is known to be a power of two when defined. Supports values with 51dbaa2376f7b3c027e895ff4bee3ae08351f3ea88Rafael Espindola /// integer or pointer type and vectors of integers. If 'OrZero' is set then 52dbaa2376f7b3c027e895ff4bee3ae08351f3ea88Rafael Espindola /// returns true if the given value is either a power of two or zero. 53dbaa2376f7b3c027e895ff4bee3ae08351f3ea88Rafael Espindola bool isKnownToBeAPowerOfTwo(Value *V, bool OrZero = false, unsigned Depth = 0); 54d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands 55d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands /// isKnownNonZero - Return true if the given value is known to be non-zero 56d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands /// when defined. For vectors return true if every element is known to be 57d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands /// non-zero when defined. Supports values with integer or pointer type and 58d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands /// vectors of integers. 593574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow bool isKnownNonZero(Value *V, const DataLayout *TD = 0, unsigned Depth = 0); 60d70d1a5c44609af091f6fc3e29193f9f4756a74fDuncan Sands 61833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner /// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use 62833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner /// this predicate to simplify operations downstream. Mask is known to be 63833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner /// zero for bits that V cannot have. 64cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// 65cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// This function is defined on values with integer type, values with pointer 66cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// type (but only if TD is non-null), and vectors of integers. In the case 67cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// where V is a vector, the mask, known zero, and known one values are the 68cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// same width as the vector element, and the bit is set only if it is true 69cf5128ec01f45d2bf7eadc20b253cb44486e473fChris Lattner /// for all of the elements in the vector. 70173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner bool MaskedValueIsZero(Value *V, const APInt &Mask, 713574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow const DataLayout *TD = 0, unsigned Depth = 0); 72173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 73173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 74173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// ComputeNumSignBits - Return the number of times the sign bit of the 75173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// register is replicated into the other bits. We know that at least 1 bit 76173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// is always equal to the sign bit (itself), but other cases can give us 77173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// information. For example, immediately after an "ashr X, 2", we know that 78173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// the top 3 bits are all equal to each other, so we return 3. 79173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// 80173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// 'Op' must have a scalar integer type. 81173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner /// 823574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow unsigned ComputeNumSignBits(Value *Op, const DataLayout *TD = 0, 83173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner unsigned Depth = 0); 84173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 852b6705f5e7c7624bd7fe486298c400f1afc15f6cVictor Hernandez /// ComputeMultiple - This function computes the integer multiple of Base that 862b6705f5e7c7624bd7fe486298c400f1afc15f6cVictor Hernandez /// equals V. If successful, it returns true and returns the multiple in 872b6705f5e7c7624bd7fe486298c400f1afc15f6cVictor Hernandez /// Multiple. If unsuccessful, it returns false. Also, if V can be 882b6705f5e7c7624bd7fe486298c400f1afc15f6cVictor Hernandez /// simplified to an integer, then the simplified V is returned in Val. Look 892b6705f5e7c7624bd7fe486298c400f1afc15f6cVictor Hernandez /// through sext only if LookThroughSExt=true. 903dbb9e64d6e9d1e8bf16f75ebe4fe59ffdf93dd3Dan Gohman bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple, 913dbb9e64d6e9d1e8bf16f75ebe4fe59ffdf93dd3Dan Gohman bool LookThroughSExt = false, 922b6705f5e7c7624bd7fe486298c400f1afc15f6cVictor Hernandez unsigned Depth = 0); 932b6705f5e7c7624bd7fe486298c400f1afc15f6cVictor Hernandez 94833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner /// CannotBeNegativeZero - Return true if we can prove that the specified FP 95833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner /// value is never equal to -0.0. 96833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner /// 97833f25d79ee28f1049f9177c3d2f4c9fbad6f643Chris Lattner bool CannotBeNegativeZero(const Value *V, unsigned Depth = 0); 98b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman 99bb89710dddf967199dfc56e8bf5d28b0003f2ee6Chris Lattner /// isBytewiseValue - If the specified value can be set by repeating the same 100bb89710dddf967199dfc56e8bf5d28b0003f2ee6Chris Lattner /// byte in memory, return the i8 value that it is represented with. This is 101bb89710dddf967199dfc56e8bf5d28b0003f2ee6Chris Lattner /// true for all i8 values obviously, but is also true for i32 0, i32 -1, 102bb89710dddf967199dfc56e8bf5d28b0003f2ee6Chris Lattner /// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated 103bb89710dddf967199dfc56e8bf5d28b0003f2ee6Chris Lattner /// byte store (e.g. i16 0x1234), return null. 104bb89710dddf967199dfc56e8bf5d28b0003f2ee6Chris Lattner Value *isBytewiseValue(Value *V); 105bb89710dddf967199dfc56e8bf5d28b0003f2ee6Chris Lattner 106dffc308c0e34617fe1ee686429f2146ff6170325Dan Gohman /// FindInsertedValue - Given an aggregrate and an sequence of indices, see if 10774fc4d968617a1652666bed8aba5e35da86373ceMatthijs Kooijman /// the scalar value indexed is already around as a register, for example if 10874fc4d968617a1652666bed8aba5e35da86373ceMatthijs Kooijman /// it were inserted directly into the aggregrate. 109977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman /// 110977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman /// If InsertBefore is not null, this function will duplicate (modified) 111977289121996f0afb781592f92a4aee1be3010feMatthijs Kooijman /// insertvalues when a part of a nested struct is extracted. 112b23d5adbc8230167e711070b9298985de4580f30Matthijs Kooijman Value *FindInsertedValue(Value *V, 113fc6d3a49867cd38954dc40936a88f1907252c6d2Jay Foad ArrayRef<unsigned> idx_range, 114464bb782fb9f873414b4ec01698c88b411564430Nick Lewycky Instruction *InsertBefore = 0); 115de9256ad2e33a203e97328e285c3909f67aad4b0Matthijs Kooijman 116ed58a6f96f605901adc0df3ca76499d52b2d1a1aChris Lattner /// GetPointerBaseWithConstantOffset - Analyze the specified pointer to see if 117ed58a6f96f605901adc0df3ca76499d52b2d1a1aChris Lattner /// it can be expressed as a base pointer plus a constant offset. Return the 118ed58a6f96f605901adc0df3ca76499d52b2d1a1aChris Lattner /// base and offset to the caller. 119ed58a6f96f605901adc0df3ca76499d52b2d1a1aChris Lattner Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, 120a070d2a0355c4993240b5206ebc1d517c151331dDan Gohman const DataLayout *TD); 121a04096580a65b6cfbe12dabf6d695f7303750c0dChris Lattner static inline const Value * 122a04096580a65b6cfbe12dabf6d695f7303750c0dChris Lattner GetPointerBaseWithConstantOffset(const Value *Ptr, int64_t &Offset, 123a070d2a0355c4993240b5206ebc1d517c151331dDan Gohman const DataLayout *TD) { 124a04096580a65b6cfbe12dabf6d695f7303750c0dChris Lattner return GetPointerBaseWithConstantOffset(const_cast<Value*>(Ptr), Offset,TD); 125a04096580a65b6cfbe12dabf6d695f7303750c0dChris Lattner } 126ed58a6f96f605901adc0df3ca76499d52b2d1a1aChris Lattner 12718c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner /// getConstantStringInfo - This function computes the length of a 1280582ae99ba75a556d6ff63b254da327d32ba036fBill Wendling /// null-terminated C string pointed to by V. If successful, it returns true 12918c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner /// and returns the string in Str. If unsuccessful, it returns false. This 13018c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner /// does not include the trailing nul character by default. If TrimAtNul is 13118c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner /// set to false, then this returns any trailing nul characters as well as any 13218c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner /// other characters that come after it. 13318c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner bool getConstantStringInfo(const Value *V, StringRef &Str, 13418c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner uint64_t Offset = 0, bool TrimAtNul = true); 13518c7f80b3e83ab584bd8572695a3cde8bafd9d3cChris Lattner 13625ec483cfca8d3a3ba8728a4a126e04b92789069Eric Christopher /// GetStringLength - If we can compute the length of the string pointed to by 13725ec483cfca8d3a3ba8728a4a126e04b92789069Eric Christopher /// the specified pointer, return 'len+1'. If we can't, return 0. 13825ec483cfca8d3a3ba8728a4a126e04b92789069Eric Christopher uint64_t GetStringLength(Value *V); 1395034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman 1405034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman /// GetUnderlyingObject - This method strips off any GEP address adjustments 1415034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman /// and pointer casts from the specified value, returning the original object 1425034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman /// being addressed. Note that the returned value has pointer type if the 1435034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman /// specified value does. If the MaxLookup value is non-zero, it limits the 1445034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman /// number of instructions to be stripped off. 1453574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow Value *GetUnderlyingObject(Value *V, const DataLayout *TD = 0, 146bd1801b5553c8be3960255a92738464e0010b6f6Dan Gohman unsigned MaxLookup = 6); 1475034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman static inline const Value * 1483574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow GetUnderlyingObject(const Value *V, const DataLayout *TD = 0, 149bd1801b5553c8be3960255a92738464e0010b6f6Dan Gohman unsigned MaxLookup = 6) { 150bd1801b5553c8be3960255a92738464e0010b6f6Dan Gohman return GetUnderlyingObject(const_cast<Value *>(V), TD, MaxLookup); 1515034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman } 1525034dd318a9dfa0dc45a3ac01e58e60f2aa2498dDan Gohman 153b401e3bd16c3d648464606d5e5b496dd61d12afcDan Gohman /// GetUnderlyingObjects - This method is similar to GetUnderlyingObject 154b401e3bd16c3d648464606d5e5b496dd61d12afcDan Gohman /// except that it can look through phi and select instructions and return 155b401e3bd16c3d648464606d5e5b496dd61d12afcDan Gohman /// multiple objects. 156b401e3bd16c3d648464606d5e5b496dd61d12afcDan Gohman void GetUnderlyingObjects(Value *V, 157b401e3bd16c3d648464606d5e5b496dd61d12afcDan Gohman SmallVectorImpl<Value *> &Objects, 1583574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow const DataLayout *TD = 0, 159b401e3bd16c3d648464606d5e5b496dd61d12afcDan Gohman unsigned MaxLookup = 6); 160b401e3bd16c3d648464606d5e5b496dd61d12afcDan Gohman 16199e0b2a8df7e3a49c0e1edd250d17604fe2fb21cNick Lewycky /// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer 16299e0b2a8df7e3a49c0e1edd250d17604fe2fb21cNick Lewycky /// are lifetime markers. 16399e0b2a8df7e3a49c0e1edd250d17604fe2fb21cNick Lewycky bool onlyUsedByLifetimeMarkers(const Value *V); 16499e0b2a8df7e3a49c0e1edd250d17604fe2fb21cNick Lewycky 165f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// isSafeToSpeculativelyExecute - Return true if the instruction does not 166f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// have any effects besides calculating the result and does not have 167f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// undefined behavior. 168f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// 169f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// This method never returns true for an instruction that returns true for 170f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// mayHaveSideEffects; however, this method also does some other checks in 171f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// addition. It checks for undefined behavior, like dividing by zero or 172f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// loading from an invalid pointer (but not for undefined results, like a 173f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// shift with a shift amount larger than the width of the result). It checks 174f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// for malloc and alloca because speculatively executing them might cause a 175f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// memory leak. It also returns false for instructions related to control 176f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// flow, specifically terminators and PHI nodes. 177f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// 178f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// This method only looks at the instruction itself and its operands, so if 179f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// this method returns true, it is safe to move the instruction as long as 180f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// the correct dominance relationships for the operands and users hold. 181f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// However, this method can return true for instructions that read memory; 182f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman /// for such instructions, moving them may change the resulting value. 183febaf8401779fedf8db7b02e499c5e39848fb9f5Dan Gohman bool isSafeToSpeculativelyExecute(const Value *V, 1843574eca1b02600bac4e625297f4ecf745f4c4f32Micah Villmow const DataLayout *TD = 0); 185f0426601977c3e386d2d26c72a2cca691dc42072Dan Gohman 186de0eb19248f3053c07a5b1dad9c47b8435458337Dan Gohman /// isKnownNonNull - Return true if this pointer couldn't possibly be null by 187de0eb19248f3053c07a5b1dad9c47b8435458337Dan Gohman /// its definition. This returns true for allocas, non-extern-weak globals 188de0eb19248f3053c07a5b1dad9c47b8435458337Dan Gohman /// and byval arguments. 189de0eb19248f3053c07a5b1dad9c47b8435458337Dan Gohman bool isKnownNonNull(const Value *V); 190de0eb19248f3053c07a5b1dad9c47b8435458337Dan Gohman 191173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner} // end namespace llvm 192173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner 193173234a68fb6ece106e77da443d87f09d5906cb9Chris Lattner#endif 194