llvm/lib/Transforms/Utils/InjectTLIMappings.cpp

   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/TargetLibraryInfo.h"
  19 #include "llvm/Analysis/VectorUtils.h"
  20 #include "llvm/IR/InstIterator.h"
  21 #include "llvm/IR/VFABIDemangler.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 variant declaration for vectorizing
  37 /// the CallInst \p CI with a vectorization factor of \p VF lanes. For each
  38 /// mapping, TLI provides a VABI prefix, which contains all information required
  39 /// to create vector function declaration.
  40 static void addVariantDeclaration(CallInst &CI, const ElementCount &VF,
  41                                   const VecDesc *VD) {
  42   Module *M = CI.getModule();
  43   FunctionType *ScalarFTy = CI.getFunctionType();
  44
  45   assert(!ScalarFTy->isVarArg() && "VarArg functions are not supported.");
  46
  47   const std::optional<VFInfo> Info = VFABI::tryDemangleForVFABI(
  48       VD->getVectorFunctionABIVariantString(), ScalarFTy);
  49
  50   assert(Info && "Failed to demangle vector variant");
  51   assert(Info->Shape.VF == VF && "Mangled name does not match VF");
  52
  53   const StringRef VFName = VD->getVectorFnName();
  54   FunctionType *VectorFTy = VFABI::createFunctionType(*Info, ScalarFTy);
  55   Function *VecFunc =
  56       Function::Create(VectorFTy, Function::ExternalLinkage, VFName, M);
  57   VecFunc->copyAttributesFrom(CI.getCalledFunction());
  58   ++NumVFDeclAdded;
  59   LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Added to the module: `" << VFName
  60                     << "` of type " << *VectorFTy << "\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(!VecFunc->size() && "VFABI attribute requires `@llvm.compiler.used` "
  65                              "only on declarations.");
  66   appendToCompilerUsed(*M, {VecFunc});
  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, bool Predicate) {
  94     const VecDesc *VD = TLI.getVectorMappingInfo(ScalarName, VF, Predicate);
  95     if (VD && !VD->getVectorFnName().empty()) {
  96       std::string MangledName = VD->getVectorFunctionABIVariantString();
  97       if (!OriginalSetOfMappings.count(MangledName)) {
  98         Mappings.push_back(MangledName);
  99         ++NumCallInjected;
 100       }
 101       Function *VariantF = M->getFunction(VD->getVectorFnName());
 102       if (!VariantF)
 103         addVariantDeclaration(CI, VF, VD);
 104     }
 105   };
 106
 107   //  All VFs in the TLI are powers of 2.
 108   ElementCount WidestFixedVF, WidestScalableVF;
 109   TLI.getWidestVF(ScalarName, WidestFixedVF, WidestScalableVF);
 110
 111   for (bool Predicated : {false, true}) {
 112     for (ElementCount VF = ElementCount::getFixed(2);
 113          ElementCount::isKnownLE(VF, WidestFixedVF); VF *= 2)
 114       AddVariantDecl(VF, Predicated);
 115
 116     for (ElementCount VF = ElementCount::getScalable(2);
 117          ElementCount::isKnownLE(VF, WidestScalableVF); VF *= 2)
 118       AddVariantDecl(VF, Predicated);
 119   }
 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 }