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 ElementCount &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 
93   auto AddVariantDecl = [&](const ElementCount &VF) {
94     const std::string TLIName =
95         std::string(TLI.getVectorizedFunction(ScalarName, VF));
96     if (!TLIName.empty()) {
97       std::string MangledName = VFABI::mangleTLIVectorName(
98           TLIName, ScalarName, CI.getNumArgOperands(), VF);
99       if (!OriginalSetOfMappings.count(MangledName)) {
100         Mappings.push_back(MangledName);
101         ++NumCallInjected;
102       }
103       Function *VariantF = M->getFunction(TLIName);
104       if (!VariantF)
105         addVariantDeclaration(CI, VF, TLIName);
106     }
107   };
108 
109   //  All VFs in the TLI are powers of 2.
110   ElementCount WidestFixedVF, WidestScalableVF;
111   TLI.getWidestVF(ScalarName, WidestFixedVF, WidestScalableVF);
112 
113   for (ElementCount VF = ElementCount::getFixed(2);
114        ElementCount::isKnownLE(VF, WidestFixedVF); VF *= 2)
115     AddVariantDecl(VF);
116 
117   // TODO: Add scalable variants once we're able to test them.
118   assert(WidestScalableVF.isZero() &&
119          "Scalable vector mappings not yet supported");
120 
121   VFABI::setVectorVariantNames(&CI, Mappings);
122 }
123 
124 static bool runImpl(const TargetLibraryInfo &TLI, Function &F) {
125   for (auto &I : instructions(F))
126     if (auto CI = dyn_cast<CallInst>(&I))
127       addMappingsFromTLI(TLI, *CI);
128   // Even if the pass adds IR attributes, the analyses are preserved.
129   return false;
130 }
131 
132 ////////////////////////////////////////////////////////////////////////////////
133 // New pass manager implementation.
134 ////////////////////////////////////////////////////////////////////////////////
135 PreservedAnalyses InjectTLIMappings::run(Function &F,
136                                          FunctionAnalysisManager &AM) {
137   const TargetLibraryInfo &TLI = AM.getResult<TargetLibraryAnalysis>(F);
138   runImpl(TLI, F);
139   // Even if the pass adds IR attributes, the analyses are preserved.
140   return PreservedAnalyses::all();
141 }
142 
143 ////////////////////////////////////////////////////////////////////////////////
144 // Legacy PM Implementation.
145 ////////////////////////////////////////////////////////////////////////////////
146 bool InjectTLIMappingsLegacy::runOnFunction(Function &F) {
147   const TargetLibraryInfo &TLI =
148       getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
149   return runImpl(TLI, F);
150 }
151 
152 void InjectTLIMappingsLegacy::getAnalysisUsage(AnalysisUsage &AU) const {
153   AU.setPreservesCFG();
154   AU.addRequired<TargetLibraryInfoWrapperPass>();
155   AU.addPreserved<TargetLibraryInfoWrapperPass>();
156   AU.addPreserved<ScalarEvolutionWrapperPass>();
157   AU.addPreserved<AAResultsWrapperPass>();
158   AU.addPreserved<LoopAccessLegacyAnalysis>();
159   AU.addPreserved<DemandedBitsWrapperPass>();
160   AU.addPreserved<OptimizationRemarkEmitterWrapperPass>();
161   AU.addPreserved<GlobalsAAWrapperPass>();
162 }
163 
164 ////////////////////////////////////////////////////////////////////////////////
165 // Legacy Pass manager initialization
166 ////////////////////////////////////////////////////////////////////////////////
167 char InjectTLIMappingsLegacy::ID = 0;
168 
169 INITIALIZE_PASS_BEGIN(InjectTLIMappingsLegacy, DEBUG_TYPE,
170                       "Inject TLI Mappings", false, false)
171 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
172 INITIALIZE_PASS_END(InjectTLIMappingsLegacy, DEBUG_TYPE, "Inject TLI Mappings",
173                     false, false)
174 
175 FunctionPass *llvm::createInjectTLIMappingsLegacyPass() {
176   return new InjectTLIMappingsLegacy();
177 }
178