1//===--- CtxInstrContextNode.h - Contextual Profile Node --------*- 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//
10// NOTE!
11// llvm/include/llvm/ProfileData/CtxInstrContextNode.h and
12// compiler-rt/lib/ctx_profile/CtxInstrContextNode.h
13// must be exact copies of each other.
14//
15// compiler-rt creates these objects as part of the instrumentation runtime for
16// contextual profiling. LLVM only consumes them to convert a contextual tree
17// to a bitstream.
18//
19//==============================================================================
20
21/// The contextual profile is a directed tree where each node has one parent. A
22/// node (ContextNode) corresponds to a function activation. The root of the
23/// tree is at a function that was marked as entrypoint to the compiler. A node
24/// stores counter values for edges and a vector of subcontexts. These are the
25/// contexts of callees. The index in the subcontext vector corresponds to the
26/// index of the callsite (as was instrumented via llvm.instrprof.callsite). At
27/// that index we find a linked list, potentially empty, of ContextNodes. Direct
28/// calls will have 0 or 1 values in the linked list, but indirect callsites may
29/// have more.
30///
31/// The ContextNode has a fixed sized header describing it - the GUID of the
32/// function, the size of the counter and callsite vectors. It is also an
33/// (intrusive) linked list for the purposes of the indirect call case above.
34///
35/// Allocation is expected to happen on an Arena. The allocation lays out inline
36/// the counter and subcontexts vectors. The class offers APIs to correctly
37/// reference the latter.
38///
39/// The layout is as follows:
40///
41/// [[declared fields][counters vector][vector of ptrs to subcontexts]]
42///
43/// See also documentation on the counters and subContexts members below.
44///
45/// The structure of the ContextNode is known to LLVM, because LLVM needs to:
46/// (1) increment counts, and
47/// (2) form a GEP for the position in the subcontext list of a callsite
48/// This means changes to LLVM contextual profile lowering and changes here
49/// must be coupled.
50/// Note: the header content isn't interesting to LLVM (other than its size)
51///
52/// Part of contextual collection is the notion of "scratch contexts". These are
53/// buffers that are "large enough" to allow for memory-safe acceses during
54/// counter increments - meaning the counter increment code in LLVM doesn't need
55/// to be concerned with memory safety. Their subcontexts never get populated,
56/// though. The runtime code here produces and recognizes them.
57
58#ifndef LLVM_PROFILEDATA_CTXINSTRCONTEXTNODE_H
59#define LLVM_PROFILEDATA_CTXINSTRCONTEXTNODE_H
60
61#include <stdint.h>
62#include <stdlib.h>
63
64namespace llvm {
65namespace ctx_profile {
66using GUID = uint64_t;
67
68class ContextNode final {
69 const GUID Guid;
70 ContextNode *const Next;
71 const uint32_t NumCounters;
72 const uint32_t NumCallsites;
73
74public:
75 ContextNode(GUID Guid, uint32_t NumCounters, uint32_t NumCallsites,
76 ContextNode *Next = nullptr)
77 : Guid(Guid), Next(Next), NumCounters(NumCounters),
78 NumCallsites(NumCallsites) {}
79
80 static inline size_t getAllocSize(uint32_t NumCounters,
81 uint32_t NumCallsites) {
82 return sizeof(ContextNode) + sizeof(uint64_t) * NumCounters +
83 sizeof(ContextNode *) * NumCallsites;
84 }
85
86 // The counters vector starts right after the static header.
87 uint64_t *counters() {
88 ContextNode *addr_after = &(this[1]);
89 return reinterpret_cast<uint64_t *>(addr_after);
90 }
91
92 uint32_t counters_size() const { return NumCounters; }
93 uint32_t callsites_size() const { return NumCallsites; }
94
95 const uint64_t *counters() const {
96 return const_cast<ContextNode *>(this)->counters();
97 }
98
99 // The subcontexts vector starts right after the end of the counters vector.
100 ContextNode **subContexts() {
101 return reinterpret_cast<ContextNode **>(&(counters()[NumCounters]));
102 }
103
104 ContextNode *const *subContexts() const {
105 return const_cast<ContextNode *>(this)->subContexts();
106 }
107
108 GUID guid() const { return Guid; }
109 ContextNode *next() const { return Next; }
110
111 size_t size() const { return getAllocSize(NumCounters, NumCallsites); }
112
113 uint64_t entrycount() const { return counters()[0]; }
114};
115
116/// The internal structure of FunctionData. This makes sure that changes to
117/// the fields of FunctionData either get automatically captured on the llvm
118/// side, or force a manual corresponding update.
119///
120/// The macro arguments (see CtxInstrProfiling.h for example):
121///
122/// PTRDECL is a macro taking 2 parameters: a type and the name of the field.
123/// The field is a pointer of that type;
124///
125/// VOLATILE_PTRDECL is the same as above, but for volatile pointers;
126///
127/// MUTEXDECL takes one parameter, the name of a field that is a mutex.
128#define CTXPROF_FUNCTION_DATA(PTRDECL, CONTEXT_PTR, VOLATILE_PTRDECL, \
129 MUTEXDECL) \
130 PTRDECL(FunctionData, Next) \
131 VOLATILE_PTRDECL(void, EntryAddress) \
132 CONTEXT_PTR \
133 VOLATILE_PTRDECL(ContextNode, FlatCtx) \
134 MUTEXDECL(Mutex)
135
136/// Abstraction for the parameter passed to `__llvm_ctx_profile_fetch`.
137/// `startContextSection` is called before any context roots are sent for
138/// writing. Then one or more `writeContextual` calls are made; finally,
139/// `endContextSection` is called.
140class ProfileWriter {
141public:
142 virtual void startContextSection() = 0;
143 virtual void writeContextual(const ctx_profile::ContextNode &RootNode,
144 const ctx_profile::ContextNode *Unhandled,
145 uint64_t TotalRootEntryCount) = 0;
146 virtual void endContextSection() = 0;
147
148 virtual void startFlatSection() = 0;
149 virtual void writeFlat(ctx_profile::GUID Guid, const uint64_t *Buffer,
150 size_t BufferSize) = 0;
151 virtual void endFlatSection() = 0;
152
153 virtual ~ProfileWriter() = default;
154};
155} // namespace ctx_profile
156} // namespace llvm
157#endif
158