PseudoProbe.h

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//===- PseudoProbe.h - Pseudo Probe IR Helpers ------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Pseudo probe IR intrinsic and dwarf discriminator manipulation routines.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_IR_PSEUDOPROBE_H
#define LLVM_IR_PSEUDOPROBE_H
 
#include <cassert>
#include <cstdint>
#include <limits>
#include <optional>
 
namespace llvm {
 
class Instruction;
 
constexpr const char *PseudoProbeDescMetadataName = "llvm.pseudo_probe_desc";
 
enum class PseudoProbeReservedId { Invalid = 0, Last = Invalid };
 
enum class PseudoProbeType { Block = 0, IndirectCall, DirectCall };
 
enum class PseudoProbeAttributes {
  Reserved = 0x1,
  Sentinel = 0x2,         // A place holder for split function entry address.
  HasDiscriminator = 0x4, // for probes with a discriminator
};
 
// The saturated distrution factor representing 100% for block probes.
constexpr static uint64_t PseudoProbeFullDistributionFactor =
    std::numeric_limits<uint64_t>::max();
 
struct PseudoProbeDwarfDiscriminator {
public:
  // The following APIs encodes/decodes per-probe information to/from a
  // 32-bit integer which is organized as:
  //  [2:0] - 0x7, this is reserved for regular discriminator,
  //          see DWARF discriminator encoding rule
  //  [18:3] - probe id
  //  [25:19] - probe distribution factor
  //  [28:26] - probe type, see PseudoProbeType
  //  [31:29] - reserved for probe attributes
  static uint32_t packProbeData(uint32_t Index, uint32_t Type, uint32_t Flags,
                                uint32_t Factor) {
    assert(Index <= 0xFFFF && "Probe index too big to encode, exceeding 2^16");
    assert(Type <= 0x7 && "Probe type too big to encode, exceeding 7");
    assert(Flags <= 0x7);
    assert(Factor <= 100 &&
           "Probe distribution factor too big to encode, exceeding 100");
    return (Index << 3) | (Factor << 19) | (Type << 26) | 0x7;
  }
 
  static uint32_t extractProbeIndex(uint32_t Value) {
    return (Value >> 3) & 0xFFFF;
  }
 
  static uint32_t extractProbeType(uint32_t Value) {
    return (Value >> 26) & 0x7;
  }
 
  static uint32_t extractProbeAttributes(uint32_t Value) {
    return (Value >> 29) & 0x7;
  }
 
  static uint32_t extractProbeFactor(uint32_t Value) {
    return (Value >> 19) & 0x7F;
  }
 
  // The saturated distrution factor representing 100% for callsites.
  constexpr static uint8_t FullDistributionFactor = 100;
};
 
class PseudoProbeDescriptor {
  uint64_t FunctionGUID;
  uint64_t FunctionHash;
 
public:
  PseudoProbeDescriptor(uint64_t GUID, uint64_t Hash)
      : FunctionGUID(GUID), FunctionHash(Hash) {}
  uint64_t getFunctionGUID() const { return FunctionGUID; }
  uint64_t getFunctionHash() const { return FunctionHash; }
};
 
struct PseudoProbe {
  uint32_t Id;
  uint32_t Type;
  uint32_t Attr;
  uint32_t Discriminator;
  // Distribution factor that estimates the portion of the real execution count.
  // A saturated distribution factor stands for 1.0 or 100%. A pesudo probe has
  // a factor with the value ranged from 0.0 to 1.0.
  float Factor;
};
 
static inline bool isSentinelProbe(uint32_t Flags) {
  return Flags & (uint32_t)PseudoProbeAttributes::Sentinel;
}
 
static inline bool hasDiscriminator(uint32_t Flags) {
  return Flags & (uint32_t)PseudoProbeAttributes::HasDiscriminator;
}
 
std::optional<PseudoProbe> extractProbe(const Instruction &Inst);
 
void setProbeDistributionFactor(Instruction &Inst, float Factor);
} // end namespace llvm
 
#endif // LLVM_IR_PSEUDOPROBE_H