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       Changed |= inferLibFuncAttributes(F, GetTLI(F));
35       Changed |= inferAttributesFromOthers(F);
36     }
37 
38   return Changed;
39 }
40 
41 PreservedAnalyses InferFunctionAttrsPass::run(Module &M,
42                                               ModuleAnalysisManager &AM) {
43   FunctionAnalysisManager &FAM =
44       AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
45   auto GetTLI = [&FAM](Function &F) -> TargetLibraryInfo & {
46     return FAM.getResult<TargetLibraryAnalysis>(F);
47   };
48 
49   if (!inferAllPrototypeAttributes(M, GetTLI))
50     // If we didn't infer anything, preserve all analyses.
51     return PreservedAnalyses::all();
52 
53   // Otherwise, we may have changed fundamental function attributes, so clear
54   // out all the passes.
55   return PreservedAnalyses::none();
56 }
57 
58 namespace {
59 struct InferFunctionAttrsLegacyPass : public ModulePass {
60   static char ID; // Pass identification, replacement for typeid
61   InferFunctionAttrsLegacyPass() : ModulePass(ID) {
62     initializeInferFunctionAttrsLegacyPassPass(
63         *PassRegistry::getPassRegistry());
64   }
65 
66   void getAnalysisUsage(AnalysisUsage &AU) const override {
67     AU.addRequired<TargetLibraryInfoWrapperPass>();
68   }
69 
70   bool runOnModule(Module &M) override {
71     if (skipModule(M))
72       return false;
73 
74     auto GetTLI = [this](Function &F) -> TargetLibraryInfo & {
75       return this->getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
76     };
77     return inferAllPrototypeAttributes(M, GetTLI);
78   }
79 };
80 }
81 
82 char InferFunctionAttrsLegacyPass::ID = 0;
83 INITIALIZE_PASS_BEGIN(InferFunctionAttrsLegacyPass, "inferattrs",
84                       "Infer set function attributes", false, false)
85 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
86 INITIALIZE_PASS_END(InferFunctionAttrsLegacyPass, "inferattrs",
87                     "Infer set function attributes", false, false)
88 
89 Pass *llvm::createInferFunctionAttrsLegacyPass() {
90   return new InferFunctionAttrsLegacyPass();
91 }
92