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      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
     49   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 
     59   static uint32_t extractProbeIndex(uint32_t Value) {
     60     return (Value >> 3) & 0xFFFF;
     61   }
     62 
     63   static uint32_t extractProbeType(uint32_t Value) {
     64     return (Value >> 26) & 0x7;
     65   }
     66 
     67   static uint32_t extractProbeAttributes(uint32_t Value) {
     68     return (Value >> 29) & 0x7;
     69   }
     70 
     71   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 
     88   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