1 //===- FunctionAttrs.h - Compute function attributes ------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 /// \file
11 /// Provides passes for computing function attributes based on interprocedural
12 /// analyses.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
17 #define LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
18 
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 AAResults;
26 class Function;
27 class Module;
28 class Pass;
29 
30 /// The three kinds of memory access relevant to 'readonly' and
31 /// 'readnone' attributes.
32 enum MemoryAccessKind {
33   MAK_ReadNone = 0,
34   MAK_ReadOnly = 1,
35   MAK_MayWrite = 2,
36   MAK_WriteOnly = 3
37 };
38 
39 /// Returns the memory access properties of this copy of the function.
40 MemoryAccessKind computeFunctionBodyMemoryAccess(Function &F, AAResults &AAR);
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