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