1 //===-- xray_fdr_log_records.h -------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file is a part of XRay, a function call tracing system.
12 //===----------------------------------------------------------------------===//
13 #ifndef XRAY_XRAY_FDR_LOG_RECORDS_H
14 #define XRAY_XRAY_FDR_LOG_RECORDS_H
16 enum class RecordType : uint8_t { Function, Metadata };
18 // A MetadataRecord encodes the kind of record in its first byte, and have 15
19 // additional bytes in the end to hold free-form data.
20 struct alignas(16) MetadataRecord {
21 // A MetadataRecord must always have a type of 1.
22 /* RecordType */ uint8_t Type : 1;
24 // Each kind of record is represented as a 7-bit value (even though we use an
25 // unsigned 8-bit enum class to do so).
26 enum class RecordKinds : uint8_t {
39 // Use 7 bits to identify this record type.
40 /* RecordKinds */ uint8_t RecordKind : 7;
42 } __attribute__((packed));
44 static_assert(sizeof(MetadataRecord) == 16, "Wrong size for MetadataRecord.");
46 struct alignas(8) FunctionRecord {
47 // A FunctionRecord must always have a type of 0.
48 /* RecordType */ uint8_t Type : 1;
49 enum class RecordKinds {
52 FunctionTailExit = 0x02,
54 /* RecordKinds */ uint8_t RecordKind : 3;
56 // We only use 28 bits of the function ID, so that we can use as few bytes as
57 // possible. This means we only support 2^28 (268,435,456) unique function ids
58 // in a single binary.
61 // We use another 4 bytes to hold the delta between the previous entry's TSC.
62 // In case we've found that the distance is greater than the allowable 32 bits
63 // (either because we are running in a different CPU and the TSC might be
64 // different then), we should use a MetadataRecord before this FunctionRecord
65 // that will contain the full TSC for that CPU, and keep this to 0.
67 } __attribute__((packed));
69 static_assert(sizeof(FunctionRecord) == 8, "Wrong size for FunctionRecord.");
71 #endif // XRAY_XRAY_FDR_LOG_RECORDS_H