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.
addVariantDeclaration(CallInst & CI,const ElementCount & VF,const VecDesc * VD)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 if (auto CC = VD->getCallingConv())
59 VecFunc->setCallingConv(*CC);
60 ++NumVFDeclAdded;
61 LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Added to the module: `" << VFName
62 << "` of type " << *VectorFTy << "\n");
63
64 // Make function declaration (without a body) "sticky" in the IR by
65 // listing it in the @llvm.compiler.used intrinsic.
66 assert(!VecFunc->size() && "VFABI attribute requires `@llvm.compiler.used` "
67 "only on declarations.");
68 appendToCompilerUsed(*M, {VecFunc});
69 LLVM_DEBUG(dbgs() << DEBUG_TYPE << ": Adding `" << VFName
70 << "` to `@llvm.compiler.used`.\n");
71 ++NumCompUsedAdded;
72 }
73
addMappingsFromTLI(const TargetLibraryInfo & TLI,CallInst & CI)74 static void addMappingsFromTLI(const TargetLibraryInfo &TLI, CallInst &CI) {
75 // This is needed to make sure we don't query the TLI for calls to
76 // bitcast of function pointers, like `%call = call i32 (i32*, ...)
77 // bitcast (i32 (...)* @goo to i32 (i32*, ...)*)(i32* nonnull %i)`,
78 // as such calls make the `isFunctionVectorizable` raise an
79 // exception.
80 if (CI.isNoBuiltin() || !CI.getCalledFunction())
81 return;
82
83 StringRef ScalarName = CI.getCalledFunction()->getName();
84
85 // Nothing to be done if the TLI thinks the function is not
86 // vectorizable.
87 if (!TLI.isFunctionVectorizable(ScalarName))
88 return;
89 SmallVector<std::string, 8> Mappings;
90 VFABI::getVectorVariantNames(CI, Mappings);
91 Module *M = CI.getModule();
92 const SetVector<StringRef> OriginalSetOfMappings(llvm::from_range, Mappings);
93
94 auto AddVariantDecl = [&](const ElementCount &VF, bool Predicate) {
95 const VecDesc *VD = TLI.getVectorMappingInfo(ScalarName, VF, Predicate);
96 if (VD && !VD->getVectorFnName().empty()) {
97 std::string MangledName = VD->getVectorFunctionABIVariantString();
98 if (!OriginalSetOfMappings.count(MangledName)) {
99 Mappings.push_back(MangledName);
100 ++NumCallInjected;
101 }
102 Function *VariantF = M->getFunction(VD->getVectorFnName());
103 if (!VariantF)
104 addVariantDeclaration(CI, VF, VD);
105 }
106 };
107
108 // All VFs in the TLI are powers of 2.
109 ElementCount WidestFixedVF, WidestScalableVF;
110 TLI.getWidestVF(ScalarName, WidestFixedVF, WidestScalableVF);
111
112 for (bool Predicated : {false, true}) {
113 for (ElementCount VF = ElementCount::getFixed(2);
114 ElementCount::isKnownLE(VF, WidestFixedVF); VF *= 2)
115 AddVariantDecl(VF, Predicated);
116
117 for (ElementCount VF = ElementCount::getScalable(2);
118 ElementCount::isKnownLE(VF, WidestScalableVF); VF *= 2)
119 AddVariantDecl(VF, Predicated);
120 }
121
122 VFABI::setVectorVariantNames(&CI, Mappings);
123 }
124
runImpl(const TargetLibraryInfo & TLI,Function & F)125 static bool runImpl(const TargetLibraryInfo &TLI, Function &F) {
126 for (auto &I : instructions(F))
127 if (auto CI = dyn_cast<CallInst>(&I))
128 addMappingsFromTLI(TLI, *CI);
129 // Even if the pass adds IR attributes, the analyses are preserved.
130 return false;
131 }
132
133 ////////////////////////////////////////////////////////////////////////////////
134 // New pass manager implementation.
135 ////////////////////////////////////////////////////////////////////////////////
run(Function & F,FunctionAnalysisManager & AM)136 PreservedAnalyses InjectTLIMappings::run(Function &F,
137 FunctionAnalysisManager &AM) {
138 const TargetLibraryInfo &TLI = AM.getResult<TargetLibraryAnalysis>(F);
139 runImpl(TLI, F);
140 // Even if the pass adds IR attributes, the analyses are preserved.
141 return PreservedAnalyses::all();
142 }
143