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/LLVMContext.h"
13 #include "llvm/IR/Module.h"
14 #include "llvm/InitializePasses.h"
15 #include "llvm/Support/Debug.h"
16 #include "llvm/Support/raw_ostream.h"
17 #include "llvm/Transforms/Utils/BuildLibCalls.h"
18 #include "llvm/Transforms/Utils/Local.h"
19 using namespace llvm;
20 
21 #define DEBUG_TYPE "inferattrs"
22 
23 static bool inferAllPrototypeAttributes(
24     Module &M, function_ref<TargetLibraryInfo &(Function &)> GetTLI) {
25   bool Changed = false;
26 
27   for (Function &F : M.functions())
28     // We only infer things using the prototype and the name; we don't need
29     // definitions.  This ensures libfuncs are annotated and also allows our
30     // CGSCC inference to avoid needing to duplicate the inference from other
31     // attribute logic on all calls to declarations (as declarations aren't
32     // explicitly visited by CGSCC passes in the new pass manager.)
33     if (F.isDeclaration() && !F.hasOptNone()) {
34       if (!F.hasFnAttribute(Attribute::NoBuiltin))
35         Changed |= inferLibFuncAttributes(F, GetTLI(F));
36       Changed |= inferAttributesFromOthers(F);
37     }
38 
39   return Changed;
40 }
41 
42 PreservedAnalyses InferFunctionAttrsPass::run(Module &M,
43                                               ModuleAnalysisManager &AM) {
44   FunctionAnalysisManager &FAM =
45       AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
46   auto GetTLI = [&FAM](Function &F) -> TargetLibraryInfo & {
47     return FAM.getResult<TargetLibraryAnalysis>(F);
48   };
49 
50   if (!inferAllPrototypeAttributes(M, GetTLI))
51     // If we didn't infer anything, preserve all analyses.
52     return PreservedAnalyses::all();
53 
54   // Otherwise, we may have changed fundamental function attributes, so clear
55   // out all the passes.
56   return PreservedAnalyses::none();
57 }
58 
59 namespace {
60 struct InferFunctionAttrsLegacyPass : public ModulePass {
61   static char ID; // Pass identification, replacement for typeid
62   InferFunctionAttrsLegacyPass() : ModulePass(ID) {
63     initializeInferFunctionAttrsLegacyPassPass(
64         *PassRegistry::getPassRegistry());
65   }
66 
67   void getAnalysisUsage(AnalysisUsage &AU) const override {
68     AU.addRequired<TargetLibraryInfoWrapperPass>();
69   }
70 
71   bool runOnModule(Module &M) override {
72     if (skipModule(M))
73       return false;
74 
75     auto GetTLI = [this](Function &F) -> TargetLibraryInfo & {
76       return this->getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
77     };
78     return inferAllPrototypeAttributes(M, GetTLI);
79   }
80 };
81 }
82 
83 char InferFunctionAttrsLegacyPass::ID = 0;
84 INITIALIZE_PASS_BEGIN(InferFunctionAttrsLegacyPass, "inferattrs",
85                       "Infer set function attributes", false, false)
86 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
87 INITIALIZE_PASS_END(InferFunctionAttrsLegacyPass, "inferattrs",
88                     "Infer set function attributes", false, false)
89 
90 Pass *llvm::createInferFunctionAttrsLegacyPass() {
91   return new InferFunctionAttrsLegacyPass();
92 }
93