1 //===- SimplifyLibCalls.h - Library call simplifier -------------*- 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 //
9 // This file exposes an interface to build some C language libcalls for
10 // optimization passes that need to call the various functions.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_TRANSFORMS_UTILS_SIMPLIFYLIBCALLS_H
15 #define LLVM_TRANSFORMS_UTILS_SIMPLIFYLIBCALLS_H
16 
17 #include "llvm/ADT/STLFunctionalExtras.h"
18 #include "llvm/Analysis/TargetLibraryInfo.h"
19 
20 namespace llvm {
21 class StringRef;
22 class Value;
23 class CallInst;
24 class DataLayout;
25 class Instruction;
26 class IRBuilderBase;
27 class Function;
28 class OptimizationRemarkEmitter;
29 class BlockFrequencyInfo;
30 class ProfileSummaryInfo;
31 
32 /// This class implements simplifications for calls to fortified library
33 /// functions (__st*cpy_chk, __memcpy_chk, __memmove_chk, __memset_chk), to,
34 /// when possible, replace them with their non-checking counterparts.
35 /// Other optimizations can also be done, but it's possible to disable them and
36 /// only simplify needless use of the checking versions (when the object size
37 /// is unknown) by passing true for OnlyLowerUnknownSize.
38 class FortifiedLibCallSimplifier {
39 private:
40   const TargetLibraryInfo *TLI;
41   bool OnlyLowerUnknownSize;
42 
43 public:
44   FortifiedLibCallSimplifier(const TargetLibraryInfo *TLI,
45                              bool OnlyLowerUnknownSize = false);
46 
47   /// Take the given call instruction and return a more
48   /// optimal value to replace the instruction with or 0 if a more
49   /// optimal form can't be found.
50   /// The call must not be an indirect call.
51   Value *optimizeCall(CallInst *CI, IRBuilderBase &B);
52 
53 private:
54   Value *optimizeMemCpyChk(CallInst *CI, IRBuilderBase &B);
55   Value *optimizeMemMoveChk(CallInst *CI, IRBuilderBase &B);
56   Value *optimizeMemSetChk(CallInst *CI, IRBuilderBase &B);
57 
58   /// Str/Stp cpy are similar enough to be handled in the same functions.
59   Value *optimizeStrpCpyChk(CallInst *CI, IRBuilderBase &B, LibFunc Func);
60   Value *optimizeStrpNCpyChk(CallInst *CI, IRBuilderBase &B, LibFunc Func);
61   Value *optimizeStrLenChk(CallInst *CI, IRBuilderBase &B);
62   Value *optimizeMemPCpyChk(CallInst *CI, IRBuilderBase &B);
63   Value *optimizeMemCCpyChk(CallInst *CI, IRBuilderBase &B);
64   Value *optimizeSNPrintfChk(CallInst *CI, IRBuilderBase &B);
65   Value *optimizeSPrintfChk(CallInst *CI,IRBuilderBase &B);
66   Value *optimizeStrCatChk(CallInst *CI, IRBuilderBase &B);
67   Value *optimizeStrLCat(CallInst *CI, IRBuilderBase &B);
68   Value *optimizeStrNCatChk(CallInst *CI, IRBuilderBase &B);
69   Value *optimizeStrLCpyChk(CallInst *CI, IRBuilderBase &B);
70   Value *optimizeVSNPrintfChk(CallInst *CI, IRBuilderBase &B);
71   Value *optimizeVSPrintfChk(CallInst *CI, IRBuilderBase &B);
72 
73   /// Checks whether the call \p CI to a fortified libcall is foldable
74   /// to the non-fortified version.
75   ///
76   /// \param CI the call to the fortified libcall.
77   ///
78   /// \param ObjSizeOp the index of the object size parameter of this chk
79   /// function. Not optional since this is mandatory.
80   ///
81   /// \param SizeOp optionally set to the parameter index of an explicit buffer
82   /// size argument. For instance, set to '2' for __strncpy_chk.
83   ///
84   /// \param StrOp optionally set to the parameter index of the source string
85   /// parameter to strcpy-like functions, where only the strlen of the source
86   /// will be writtin into the destination.
87   ///
88   /// \param FlagsOp optionally set to the parameter index of a 'flags'
89   /// parameter. These are used by an implementation to opt-into stricter
90   /// checking.
91   bool isFortifiedCallFoldable(CallInst *CI, unsigned ObjSizeOp,
92                                std::optional<unsigned> SizeOp = std::nullopt,
93                                std::optional<unsigned> StrOp = std::nullopt,
94                                std::optional<unsigned> FlagsOp = std::nullopt);
95 };
96 
97 /// LibCallSimplifier - This class implements a collection of optimizations
98 /// that replace well formed calls to library functions with a more optimal
99 /// form.  For example, replacing 'printf("Hello!")' with 'puts("Hello!")'.
100 class LibCallSimplifier {
101 private:
102   FortifiedLibCallSimplifier FortifiedSimplifier;
103   const DataLayout &DL;
104   const TargetLibraryInfo *TLI;
105   OptimizationRemarkEmitter &ORE;
106   BlockFrequencyInfo *BFI;
107   ProfileSummaryInfo *PSI;
108   bool UnsafeFPShrink = false;
109   function_ref<void(Instruction *, Value *)> Replacer;
110   function_ref<void(Instruction *)> Eraser;
111 
112   /// Internal wrapper for RAUW that is the default implementation.
113   ///
114   /// Other users may provide an alternate function with this signature instead
115   /// of this one.
replaceAllUsesWithDefault(Instruction * I,Value * With)116   static void replaceAllUsesWithDefault(Instruction *I, Value *With) {
117     I->replaceAllUsesWith(With);
118   }
119 
120   /// Internal wrapper for eraseFromParent that is the default implementation.
eraseFromParentDefault(Instruction * I)121   static void eraseFromParentDefault(Instruction *I) { I->eraseFromParent(); }
122 
123   /// Replace an instruction's uses with a value using our replacer.
124   void replaceAllUsesWith(Instruction *I, Value *With);
125 
126   /// Erase an instruction from its parent with our eraser.
127   void eraseFromParent(Instruction *I);
128 
129   /// Replace an instruction with a value and erase it from its parent.
substituteInParent(Instruction * I,Value * With)130   void substituteInParent(Instruction *I, Value *With) {
131     replaceAllUsesWith(I, With);
132     eraseFromParent(I);
133   }
134 
135 public:
136   LibCallSimplifier(
137       const DataLayout &DL, const TargetLibraryInfo *TLI,
138       OptimizationRemarkEmitter &ORE,
139       BlockFrequencyInfo *BFI, ProfileSummaryInfo *PSI,
140       function_ref<void(Instruction *, Value *)> Replacer =
141           &replaceAllUsesWithDefault,
142       function_ref<void(Instruction *)> Eraser = &eraseFromParentDefault);
143 
144   /// optimizeCall - Take the given call instruction and return a more
145   /// optimal value to replace the instruction with or 0 if a more
146   /// optimal form can't be found.  Note that the returned value may
147   /// be equal to the instruction being optimized.  In this case all
148   /// other instructions that use the given instruction were modified
149   /// and the given instruction is dead.
150   /// The call must not be an indirect call.
151   Value *optimizeCall(CallInst *CI, IRBuilderBase &B);
152 
153 private:
154   // String and Memory Library Call Optimizations
155   Value *optimizeStrCat(CallInst *CI, IRBuilderBase &B);
156   Value *optimizeStrNCat(CallInst *CI, IRBuilderBase &B);
157   Value *optimizeStrChr(CallInst *CI, IRBuilderBase &B);
158   Value *optimizeStrRChr(CallInst *CI, IRBuilderBase &B);
159   Value *optimizeStrCmp(CallInst *CI, IRBuilderBase &B);
160   Value *optimizeStrNCmp(CallInst *CI, IRBuilderBase &B);
161   Value *optimizeStrNDup(CallInst *CI, IRBuilderBase &B);
162   Value *optimizeStrCpy(CallInst *CI, IRBuilderBase &B);
163   Value *optimizeStpCpy(CallInst *CI, IRBuilderBase &B);
164   Value *optimizeStrLCpy(CallInst *CI, IRBuilderBase &B);
165   Value *optimizeStrNCpy(CallInst *CI, IRBuilderBase &B);
166   Value *optimizeStrLen(CallInst *CI, IRBuilderBase &B);
167   Value *optimizeStrNLen(CallInst *CI, IRBuilderBase &B);
168   Value *optimizeStrPBrk(CallInst *CI, IRBuilderBase &B);
169   Value *optimizeStrTo(CallInst *CI, IRBuilderBase &B);
170   Value *optimizeStrSpn(CallInst *CI, IRBuilderBase &B);
171   Value *optimizeStrCSpn(CallInst *CI, IRBuilderBase &B);
172   Value *optimizeStrStr(CallInst *CI, IRBuilderBase &B);
173   Value *optimizeMemChr(CallInst *CI, IRBuilderBase &B);
174   Value *optimizeMemRChr(CallInst *CI, IRBuilderBase &B);
175   Value *optimizeMemCmp(CallInst *CI, IRBuilderBase &B);
176   Value *optimizeBCmp(CallInst *CI, IRBuilderBase &B);
177   Value *optimizeMemCmpBCmpCommon(CallInst *CI, IRBuilderBase &B);
178   Value *optimizeMemCCpy(CallInst *CI, IRBuilderBase &B);
179   Value *optimizeMemPCpy(CallInst *CI, IRBuilderBase &B);
180   Value *optimizeMemCpy(CallInst *CI, IRBuilderBase &B);
181   Value *optimizeMemMove(CallInst *CI, IRBuilderBase &B);
182   Value *optimizeMemSet(CallInst *CI, IRBuilderBase &B);
183   Value *optimizeRealloc(CallInst *CI, IRBuilderBase &B);
184   Value *optimizeWcslen(CallInst *CI, IRBuilderBase &B);
185   Value *optimizeBCopy(CallInst *CI, IRBuilderBase &B);
186 
187   // Helper to optimize stpncpy and strncpy.
188   Value *optimizeStringNCpy(CallInst *CI, bool RetEnd, IRBuilderBase &B);
189   // Wrapper for all String/Memory Library Call Optimizations
190   Value *optimizeStringMemoryLibCall(CallInst *CI, IRBuilderBase &B);
191 
192   // Math Library Optimizations
193   Value *optimizeCAbs(CallInst *CI, IRBuilderBase &B);
194   Value *optimizePow(CallInst *CI, IRBuilderBase &B);
195   Value *replacePowWithExp(CallInst *Pow, IRBuilderBase &B);
196   Value *replacePowWithSqrt(CallInst *Pow, IRBuilderBase &B);
197   Value *optimizeExp2(CallInst *CI, IRBuilderBase &B);
198   Value *optimizeFMinFMax(CallInst *CI, IRBuilderBase &B);
199   Value *optimizeLog(CallInst *CI, IRBuilderBase &B);
200   Value *optimizeSqrt(CallInst *CI, IRBuilderBase &B);
201   Value *optimizeSinCosPi(CallInst *CI, IRBuilderBase &B);
202   Value *optimizeTan(CallInst *CI, IRBuilderBase &B);
203   // Wrapper for all floating point library call optimizations
204   Value *optimizeFloatingPointLibCall(CallInst *CI, LibFunc Func,
205                                       IRBuilderBase &B);
206 
207   // Integer Library Call Optimizations
208   Value *optimizeFFS(CallInst *CI, IRBuilderBase &B);
209   Value *optimizeFls(CallInst *CI, IRBuilderBase &B);
210   Value *optimizeAbs(CallInst *CI, IRBuilderBase &B);
211   Value *optimizeIsDigit(CallInst *CI, IRBuilderBase &B);
212   Value *optimizeIsAscii(CallInst *CI, IRBuilderBase &B);
213   Value *optimizeToAscii(CallInst *CI, IRBuilderBase &B);
214   Value *optimizeAtoi(CallInst *CI, IRBuilderBase &B);
215   Value *optimizeStrToInt(CallInst *CI, IRBuilderBase &B, bool AsSigned);
216 
217   // Formatting and IO Library Call Optimizations
218   Value *optimizeErrorReporting(CallInst *CI, IRBuilderBase &B,
219                                 int StreamArg = -1);
220   Value *optimizePrintF(CallInst *CI, IRBuilderBase &B);
221   Value *optimizeSPrintF(CallInst *CI, IRBuilderBase &B);
222   Value *optimizeSnPrintF(CallInst *CI, IRBuilderBase &B);
223   Value *optimizeFPrintF(CallInst *CI, IRBuilderBase &B);
224   Value *optimizeFWrite(CallInst *CI, IRBuilderBase &B);
225   Value *optimizeFPuts(CallInst *CI, IRBuilderBase &B);
226   Value *optimizePuts(CallInst *CI, IRBuilderBase &B);
227 
228   // Helper methods
229   Value* emitSnPrintfMemCpy(CallInst *CI, Value *StrArg, StringRef Str,
230                             uint64_t N, IRBuilderBase &B);
231   Value *emitStrLenMemCpy(Value *Src, Value *Dst, uint64_t Len,
232                           IRBuilderBase &B);
233   void classifyArgUse(Value *Val, Function *F, bool IsFloat,
234                       SmallVectorImpl<CallInst *> &SinCalls,
235                       SmallVectorImpl<CallInst *> &CosCalls,
236                       SmallVectorImpl<CallInst *> &SinCosCalls);
237   Value *optimizePrintFString(CallInst *CI, IRBuilderBase &B);
238   Value *optimizeSPrintFString(CallInst *CI, IRBuilderBase &B);
239   Value *optimizeSnPrintFString(CallInst *CI, IRBuilderBase &B);
240   Value *optimizeFPrintFString(CallInst *CI, IRBuilderBase &B);
241 
242   /// hasFloatVersion - Checks if there is a float version of the specified
243   /// function by checking for an existing function with name FuncName + f
244   bool hasFloatVersion(const Module *M, StringRef FuncName);
245 
246   /// Shared code to optimize strlen+wcslen and strnlen+wcsnlen.
247   Value *optimizeStringLength(CallInst *CI, IRBuilderBase &B, unsigned CharSize,
248                               Value *Bound = nullptr);
249 };
250 } // End llvm namespace
251 
252 #endif
253