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