1 //===- PseudoProbe.h - Pseudo Probe IR Helpers ------------------*- 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 // Pseudo probe IR intrinsic and dwarf discriminator manipulation routines.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_IR_PSEUDOPROBE_H
14 #define LLVM_IR_PSEUDOPROBE_H
15 
16 #include "llvm/ADT/Optional.h"
17 #include <cassert>
18 #include <cstdint>
19 #include <limits>
20 
21 namespace llvm {
22 
23 class Instruction;
24 class BasicBlock;
25 
26 constexpr const char *PseudoProbeDescMetadataName = "llvm.pseudo_probe_desc";
27 
28 enum class PseudoProbeType { Block = 0, IndirectCall, DirectCall };
29 
30 enum class PseudoProbeAttributes {
31   Reserved = 0x1, // Reserved for future use.
32   Dangling = 0x2, // The probe is dangling.
33 };
34 
35 // The saturated distrution factor representing 100% for block probes.
36 constexpr static uint64_t PseudoProbeFullDistributionFactor =
37     std::numeric_limits<uint64_t>::max();
38 
39 struct PseudoProbeDwarfDiscriminator {
40 public:
41   // The following APIs encodes/decodes per-probe information to/from a
42   // 32-bit integer which is organized as:
43   //  [2:0] - 0x7, this is reserved for regular discriminator,
44   //          see DWARF discriminator encoding rule
45   //  [18:3] - probe id
46   //  [25:19] - probe distribution factor
47   //  [28:26] - probe type, see PseudoProbeType
48   //  [31:29] - reserved for probe attributes
packProbeDataPseudoProbeDwarfDiscriminator49   static uint32_t packProbeData(uint32_t Index, uint32_t Type, uint32_t Flags,
50                                 uint32_t Factor) {
51     assert(Index <= 0xFFFF && "Probe index too big to encode, exceeding 2^16");
52     assert(Type <= 0x7 && "Probe type too big to encode, exceeding 7");
53     assert(Flags <= 0x7);
54     assert(Factor <= 100 &&
55            "Probe distribution factor too big to encode, exceeding 100");
56     return (Index << 3) | (Factor << 19) | (Type << 26) | 0x7;
57   }
58 
extractProbeIndexPseudoProbeDwarfDiscriminator59   static uint32_t extractProbeIndex(uint32_t Value) {
60     return (Value >> 3) & 0xFFFF;
61   }
62 
extractProbeTypePseudoProbeDwarfDiscriminator63   static uint32_t extractProbeType(uint32_t Value) {
64     return (Value >> 26) & 0x7;
65   }
66 
extractProbeAttributesPseudoProbeDwarfDiscriminator67   static uint32_t extractProbeAttributes(uint32_t Value) {
68     return (Value >> 29) & 0x7;
69   }
70 
extractProbeFactorPseudoProbeDwarfDiscriminator71   static uint32_t extractProbeFactor(uint32_t Value) {
72     return (Value >> 19) & 0x7F;
73   }
74 
75   // The saturated distrution factor representing 100% for callsites.
76   constexpr static uint8_t FullDistributionFactor = 100;
77 };
78 
79 struct PseudoProbe {
80   uint32_t Id;
81   uint32_t Type;
82   uint32_t Attr;
83   // Distribution factor that estimates the portion of the real execution count.
84   // A saturated distribution factor stands for 1.0 or 100%. A pesudo probe has
85   // a factor with the value ranged from 0.0 to 1.0.
86   float Factor;
87 
isDanglingPseudoProbe88   bool isDangling() const {
89     return Attr & (uint32_t)PseudoProbeAttributes::Dangling;
90   }
91 };
92 
93 Optional<PseudoProbe> extractProbe(const Instruction &Inst);
94 
95 void setProbeDistributionFactor(Instruction &Inst, float Factor);
96 
97 bool moveAndDanglePseudoProbes(BasicBlock *From, Instruction *To);
98 
99 bool removeRedundantPseudoProbes(BasicBlock *Block);
100 } // end namespace llvm
101 
102 #endif // LLVM_IR_PSEUDOPROBE_H
103