1 //===- InjectTLIMAppings.cpp - TLI to VFABI attribute injection  ----------===//
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 // Populates the VFABI attribute with the scalar-to-vector mappings
10 // from the TargetLibraryInfo.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Transforms/Utils/InjectTLIMappings.h"
15 #include "llvm/ADT/Statistic.h"
16 #include "llvm/Analysis/DemandedBits.h"
17 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
18 #include "llvm/Analysis/VectorUtils.h"
19 #include "llvm/IR/InstIterator.h"
20 #include "llvm/IR/IntrinsicInst.h"
21 #include "llvm/Transforms/Utils.h"
22 #include "llvm/Transforms/Utils/ModuleUtils.h"
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "inject-tli-mappings"
27 
28 STATISTIC(NumCallInjected,
29           "Number of calls in which the mappings have been injected.");
30 
31 STATISTIC(NumVFDeclAdded,
32           "Number of function declarations that have been added.");
33 STATISTIC(NumCompUsedAdded,
34           "Number of `@llvm.compiler.used` operands that have been added.");
35 
36 /// Helper function to map the TLI name to a strings that holds
37 /// scalar-to-vector mapping.
38 ///
39 ///    _ZGV<isa><mask><vlen><vparams>_<scalarname>(<vectorname>)
40 ///
41 /// where:
42 ///
43 /// <isa> = "_LLVM_"
44 /// <mask> = "N". Note: TLI does not support masked interfaces.
45 /// <vlen> = Number of concurrent lanes, stored in the `VectorizationFactor`
46 ///          field of the `VecDesc` struct.
47 /// <vparams> = "v", as many as are the number of parameters of CI.
48 /// <scalarname> = the name of the scalar function called by CI.
49 /// <vectorname> = the name of the vector function mapped by the TLI.
50 static std::string mangleTLIName(StringRef VectorName, const CallInst &CI,
51                                  unsigned VF) {
52   SmallString<256> Buffer;
53   llvm::raw_svector_ostream Out(Buffer);
54   Out << "_ZGV" << VFABI::_LLVM_ << "N" << VF;
55   for (unsigned I = 0; I < CI.getNumArgOperands(); ++I)
56     Out << "v";
57   Out << "_" << CI.getCalledFunction()->getName() << "(" << VectorName << ")";
58   return std::string(Out.str());
59 }
60 
61 /// A helper function that adds the vector function declaration that
62 /// vectorizes the CallInst CI with a vectorization factor of VF
63 /// lanes. The TLI assumes that all parameters and the return type of
64 /// CI (other than void) need to be widened to a VectorType of VF
65 /// lanes.
66 static void addVariantDeclaration(CallInst &CI, const unsigned VF,
67                                   const StringRef VFName) {
68   Module *M = CI.getModule();
69 
70   // Add function declaration.
71   Type *RetTy = ToVectorTy(CI.getType(), VF);
72   SmallVector<Type *, 4> Tys;
73   for (Value *ArgOperand : CI.arg_operands())
74     Tys.push_back(ToVectorTy(ArgOperand->getType(), VF));
75   assert(!CI.getFunctionType()->isVarArg() &&
76          "VarArg functions are not supported.");
77   FunctionType *FTy = FunctionType::get(RetTy, Tys, /*isVarArg=*/false);
78   Function *VectorF =
79       Function::Create(FTy, Function::ExternalLinkage, VFName, M);
80   VectorF->copyAttributesFrom(CI.getCalledFunction());
81   ++NumVFDeclAdded;
82   LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Added to the module: `" << VFName
83                     << "` of type " << *(VectorF->getType()) << "\n");
84 
85   // Make function declaration (without a body) "sticky" in the IR by
86   // listing it in the @llvm.compiler.used intrinsic.
87   assert(!VectorF->size() && "VFABI attribute requires `@llvm.compiler.used` "
88                              "only on declarations.");
89   appendToCompilerUsed(*M, {VectorF});
90   LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Adding `" << VFName
91                     << "` to `@llvm.compiler.used`.\n");
92   ++NumCompUsedAdded;
93 }
94 
95 static void addMappingsFromTLI(const TargetLibraryInfo &TLI, CallInst &CI) {
96   // This is needed to make sure we don't query the TLI for calls to
97   // bitcast of function pointers, like `%call = call i32 (i32*, ...)
98   // bitcast (i32 (...)* @goo to i32 (i32*, ...)*)(i32* nonnull %i)`,
99   // as such calls make the `isFunctionVectorizable` raise an
100   // exception.
101   if (CI.isNoBuiltin() || !CI.getCalledFunction())
102     return;
103 
104   const std::string ScalarName = std::string(CI.getCalledFunction()->getName());
105   // Nothing to be done if the TLI thinks the function is not
106   // vectorizable.
107   if (!TLI.isFunctionVectorizable(ScalarName))
108     return;
109   SmallVector<std::string, 8> Mappings;
110   VFABI::getVectorVariantNames(CI, Mappings);
111   Module *M = CI.getModule();
112   const SetVector<StringRef> OriginalSetOfMappings(Mappings.begin(),
113                                                    Mappings.end());
114   //  All VFs in the TLI are powers of 2.
115   for (unsigned VF = 2, WidestVF = TLI.getWidestVF(ScalarName); VF <= WidestVF;
116        VF *= 2) {
117     const std::string TLIName =
118         std::string(TLI.getVectorizedFunction(ScalarName, VF));
119     if (!TLIName.empty()) {
120       std::string MangledName = mangleTLIName(TLIName, CI, VF);
121       if (!OriginalSetOfMappings.count(MangledName)) {
122         Mappings.push_back(MangledName);
123         ++NumCallInjected;
124       }
125       Function *VariantF = M->getFunction(TLIName);
126       if (!VariantF)
127         addVariantDeclaration(CI, VF, TLIName);
128     }
129   }
130 
131   VFABI::setVectorVariantNames(&CI, Mappings);
132 }
133 
134 static bool runImpl(const TargetLibraryInfo &TLI, Function &F) {
135   for (auto &I : instructions(F))
136     if (auto CI = dyn_cast<CallInst>(&I))
137       addMappingsFromTLI(TLI, *CI);
138   // Even if the pass adds IR attributes, the analyses are preserved.
139   return false;
140 }
141 
142 ////////////////////////////////////////////////////////////////////////////////
143 // New pass manager implementation.
144 ////////////////////////////////////////////////////////////////////////////////
145 PreservedAnalyses InjectTLIMappings::run(Function &F,
146                                          FunctionAnalysisManager &AM) {
147   const TargetLibraryInfo &TLI = AM.getResult<TargetLibraryAnalysis>(F);
148   runImpl(TLI, F);
149   // Even if the pass adds IR attributes, the analyses are preserved.
150   return PreservedAnalyses::all();
151 }
152 
153 ////////////////////////////////////////////////////////////////////////////////
154 // Legacy PM Implementation.
155 ////////////////////////////////////////////////////////////////////////////////
156 bool InjectTLIMappingsLegacy::runOnFunction(Function &F) {
157   const TargetLibraryInfo &TLI =
158       getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
159   return runImpl(TLI, F);
160 }
161 
162 void InjectTLIMappingsLegacy::getAnalysisUsage(AnalysisUsage &AU) const {
163   AU.setPreservesCFG();
164   AU.addRequired<TargetLibraryInfoWrapperPass>();
165   AU.addPreserved<TargetLibraryInfoWrapperPass>();
166   AU.addPreserved<ScalarEvolutionWrapperPass>();
167   AU.addPreserved<AAResultsWrapperPass>();
168   AU.addPreserved<LoopAccessLegacyAnalysis>();
169   AU.addPreserved<DemandedBitsWrapperPass>();
170   AU.addPreserved<OptimizationRemarkEmitterWrapperPass>();
171 }
172 
173 ////////////////////////////////////////////////////////////////////////////////
174 // Legacy Pass manager initialization
175 ////////////////////////////////////////////////////////////////////////////////
176 char InjectTLIMappingsLegacy::ID = 0;
177 
178 INITIALIZE_PASS_BEGIN(InjectTLIMappingsLegacy, DEBUG_TYPE,
179                       "Inject TLI Mappings", false, false)
180 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
181 INITIALIZE_PASS_END(InjectTLIMappingsLegacy, DEBUG_TYPE, "Inject TLI Mappings",
182                     false, false)
183 
184 FunctionPass *llvm::createInjectTLIMappingsLegacyPass() {
185   return new InjectTLIMappingsLegacy();
186 }
187