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 class Pass;
30 
31 /// Returns the memory access properties of this copy of the function.
32 FunctionModRefBehavior computeFunctionBodyMemoryAccess(Function &F,
33                                                        AAResults &AAR);
34 
35 /// Propagate function attributes for function summaries along the index's
36 /// callgraph during thinlink
37 bool thinLTOPropagateFunctionAttrs(
38     ModuleSummaryIndex &Index,
39     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
40         isPrevailing);
41 
42 /// Computes function attributes in post-order over the call graph.
43 ///
44 /// By operating in post-order, this pass computes precise attributes for
45 /// called functions prior to processsing their callers. This "bottom-up"
46 /// approach allows powerful interprocedural inference of function attributes
47 /// like memory access patterns, etc. It can discover functions that do not
48 /// access memory, or only read memory, and give them the readnone/readonly
49 /// attribute. It also discovers function arguments that are not captured by
50 /// the function and marks them with the nocapture attribute.
51 struct PostOrderFunctionAttrsPass : PassInfoMixin<PostOrderFunctionAttrsPass> {
52   PreservedAnalyses run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM,
53                         LazyCallGraph &CG, CGSCCUpdateResult &UR);
54 };
55 
56 /// Create a legacy pass manager instance of a pass to compute function attrs
57 /// in post-order.
58 Pass *createPostOrderFunctionAttrsLegacyPass();
59 
60 /// A pass to do RPO deduction and propagation of function attributes.
61 ///
62 /// This pass provides a general RPO or "top down" propagation of
63 /// function attributes. For a few (rare) cases, we can deduce significantly
64 /// more about function attributes by working in RPO, so this pass
65 /// provides the complement to the post-order pass above where the majority of
66 /// deduction is performed.
67 // FIXME: Currently there is no RPO CGSCC pass structure to slide into and so
68 // this is a boring module pass, but eventually it should be an RPO CGSCC pass
69 // when such infrastructure is available.
70 class ReversePostOrderFunctionAttrsPass
71     : public PassInfoMixin<ReversePostOrderFunctionAttrsPass> {
72 public:
73   PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
74 };
75 
76 } // end namespace llvm
77 
78 #endif // LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
79