1 //===- InferFunctionAttrs.cpp - Infer implicit function attributes --------===//
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 #include "llvm/Transforms/IPO/InferFunctionAttrs.h"
10 #include "llvm/Analysis/TargetLibraryInfo.h"
11 #include "llvm/IR/Function.h"
12 #include "llvm/IR/Module.h"
13 #include "llvm/InitializePasses.h"
14 #include "llvm/Transforms/Utils/BuildLibCalls.h"
15 #include "llvm/Transforms/Utils/Local.h"
16 using namespace llvm;
17 
18 #define DEBUG_TYPE "inferattrs"
19 
20 static bool inferAllPrototypeAttributes(
21     Module &M, function_ref<TargetLibraryInfo &(Function &)> GetTLI) {
22   bool Changed = false;
23 
24   for (Function &F : M.functions())
25     // We only infer things using the prototype and the name; we don't need
26     // definitions.  This ensures libfuncs are annotated and also allows our
27     // CGSCC inference to avoid needing to duplicate the inference from other
28     // attribute logic on all calls to declarations (as declarations aren't
29     // explicitly visited by CGSCC passes in the new pass manager.)
30     if (F.isDeclaration() && !F.hasOptNone()) {
31       if (!F.hasFnAttribute(Attribute::NoBuiltin))
32         Changed |= inferNonMandatoryLibFuncAttrs(F, GetTLI(F));
33       Changed |= inferAttributesFromOthers(F);
34     }
35 
36   return Changed;
37 }
38 
39 PreservedAnalyses InferFunctionAttrsPass::run(Module &M,
40                                               ModuleAnalysisManager &AM) {
41   FunctionAnalysisManager &FAM =
42       AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
43   auto GetTLI = [&FAM](Function &F) -> TargetLibraryInfo & {
44     return FAM.getResult<TargetLibraryAnalysis>(F);
45   };
46 
47   if (!inferAllPrototypeAttributes(M, GetTLI))
48     // If we didn't infer anything, preserve all analyses.
49     return PreservedAnalyses::all();
50 
51   // Otherwise, we may have changed fundamental function attributes, so clear
52   // out all the passes.
53   return PreservedAnalyses::none();
54 }
55 
56 namespace {
57 struct InferFunctionAttrsLegacyPass : public ModulePass {
58   static char ID; // Pass identification, replacement for typeid
59   InferFunctionAttrsLegacyPass() : ModulePass(ID) {
60     initializeInferFunctionAttrsLegacyPassPass(
61         *PassRegistry::getPassRegistry());
62   }
63 
64   void getAnalysisUsage(AnalysisUsage &AU) const override {
65     AU.addRequired<TargetLibraryInfoWrapperPass>();
66   }
67 
68   bool runOnModule(Module &M) override {
69     if (skipModule(M))
70       return false;
71 
72     auto GetTLI = [this](Function &F) -> TargetLibraryInfo & {
73       return this->getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
74     };
75     return inferAllPrototypeAttributes(M, GetTLI);
76   }
77 };
78 }
79 
80 char InferFunctionAttrsLegacyPass::ID = 0;
81 INITIALIZE_PASS_BEGIN(InferFunctionAttrsLegacyPass, "inferattrs",
82                       "Infer set function attributes", false, false)
83 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
84 INITIALIZE_PASS_END(InferFunctionAttrsLegacyPass, "inferattrs",
85                     "Infer set function attributes", false, false)
86 
87 Pass *llvm::createInferFunctionAttrsLegacyPass() {
88   return new InferFunctionAttrsLegacyPass();
89 }
90