1 //===- FunctionAttrs.h - Compute function attributes ------------*- C++ -*-===//
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 /// \file
10 /// Provides passes for computing function attributes based on interprocedural
11 /// analyses.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
16 #define LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
17 
18 #include "llvm/Analysis/AliasAnalysis.h"
19 #include "llvm/Analysis/CGSCCPassManager.h"
20 #include "llvm/Analysis/LazyCallGraph.h"
21 #include "llvm/IR/PassManager.h"
22 
23 namespace llvm {
24 
25 class GlobalValueSummary;
26 class ModuleSummaryIndex;
27 class Function;
28 class Module;
29 
30 /// Returns the memory access properties of this copy of the function.
31 MemoryEffects computeFunctionBodyMemoryAccess(Function &F, AAResults &AAR);
32 
33 /// Propagate function attributes for function summaries along the index's
34 /// callgraph during thinlink
35 bool thinLTOPropagateFunctionAttrs(
36     ModuleSummaryIndex &Index,
37     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
38         isPrevailing);
39 
40 /// Computes function attributes in post-order over the call graph.
41 ///
42 /// By operating in post-order, this pass computes precise attributes for
43 /// called functions prior to processsing their callers. This "bottom-up"
44 /// approach allows powerful interprocedural inference of function attributes
45 /// like memory access patterns, etc. It can discover functions that do not
46 /// access memory, or only read memory, and give them the readnone/readonly
47 /// attribute. It also discovers function arguments that are not captured by
48 /// the function and marks them with the nocapture attribute.
49 struct PostOrderFunctionAttrsPass : PassInfoMixin<PostOrderFunctionAttrsPass> {
50   PostOrderFunctionAttrsPass(bool SkipNonRecursive = false)
51       : SkipNonRecursive(SkipNonRecursive) {}
52   PreservedAnalyses run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM,
53                         LazyCallGraph &CG, CGSCCUpdateResult &UR);
54 
55   void printPipeline(raw_ostream &OS,
56                      function_ref<StringRef(StringRef)> MapClassName2PassName);
57 
58 private:
59   bool SkipNonRecursive;
60 };
61 
62 /// A pass to do RPO deduction and propagation of function attributes.
63 ///
64 /// This pass provides a general RPO or "top down" propagation of
65 /// function attributes. For a few (rare) cases, we can deduce significantly
66 /// more about function attributes by working in RPO, so this pass
67 /// provides the complement to the post-order pass above where the majority of
68 /// deduction is performed.
69 // FIXME: Currently there is no RPO CGSCC pass structure to slide into and so
70 // this is a boring module pass, but eventually it should be an RPO CGSCC pass
71 // when such infrastructure is available.
72 class ReversePostOrderFunctionAttrsPass
73     : public PassInfoMixin<ReversePostOrderFunctionAttrsPass> {
74 public:
75   PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
76 };
77 
78 } // end namespace llvm
79 
80 #endif // LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
81