include/llvm/MCA/Support.h

   1 //===--------------------- Support.h ----------------------------*- 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 /// \file
   9 ///
  10 /// Helper functions used by various pipeline components.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_MCA_SUPPORT_H
  15 #define LLVM_MCA_SUPPORT_H
  16
  17 #include "llvm/ADT/ArrayRef.h"
  18 #include "llvm/ADT/SmallVector.h"
  19 #include "llvm/MC/MCSchedule.h"
  20 #include "llvm/Support/Error.h"
  21
  22 namespace llvm {
  23 namespace mca {
  24
  25 template <typename T>
  26 class InstructionError : public ErrorInfo<InstructionError<T>> {
  27 public:
  28   static char ID;
  29   std::string Message;
  30   const T &Inst;
  31
  32   InstructionError(std::string M, const T &MCI)
  33       : Message(std::move(M)), Inst(MCI) {}
  34
  35   void log(raw_ostream &OS) const override { OS << Message; }
  36
  37   std::error_code convertToErrorCode() const override {
  38     return inconvertibleErrorCode();
  39   }
  40 };
  41
  42 template <typename T> char InstructionError<T>::ID;
  43
  44 /// This class represents the number of cycles per resource (fractions of
  45 /// cycles).  That quantity is managed here as a ratio, and accessed via the
  46 /// double cast-operator below.  The two quantities, number of cycles and
  47 /// number of resources, are kept separate.  This is used by the
  48 /// ResourcePressureView to calculate the average resource cycles
  49 /// per instruction/iteration.
  50 class ResourceCycles {
  51   unsigned Numerator, Denominator;
  52
  53 public:
  54   ResourceCycles() : Numerator(0), Denominator(1) {}
  55   ResourceCycles(unsigned Cycles, unsigned ResourceUnits = 1)
  56       : Numerator(Cycles), Denominator(ResourceUnits) {}
  57
  58   operator double() const {
  59     assert(Denominator && "Invalid denominator (must be non-zero).");
  60     return (Denominator == 1) ? Numerator : (double)Numerator / Denominator;
  61   }
  62
  63   unsigned getNumerator() const { return Numerator; }
  64   unsigned getDenominator() const { return Denominator; }
  65
  66   // Add the components of RHS to this instance.  Instead of calculating
  67   // the final value here, we keep track of the numerator and denominator
  68   // separately, to reduce floating point error.
  69   ResourceCycles &operator+=(const ResourceCycles &RHS);
  70 };
  71
  72 /// Populates vector Masks with processor resource masks.
  73 ///
  74 /// The number of bits set in a mask depends on the processor resource type.
  75 /// Each processor resource mask has at least one bit set. For groups, the
  76 /// number of bits set in the mask is equal to the cardinality of the group plus
  77 /// one. Excluding the most significant bit, the remaining bits in the mask
  78 /// identify processor resources that are part of the group.
  79 ///
  80 /// Example:
  81 ///
  82 ///  ResourceA  -- Mask: 0b001
  83 ///  ResourceB  -- Mask: 0b010
  84 ///  ResourceAB -- Mask: 0b100 U (ResourceA::Mask | ResourceB::Mask) == 0b111
  85 ///
  86 /// ResourceAB is a processor resource group containing ResourceA and ResourceB.
  87 /// Each resource mask uniquely identifies a resource; both ResourceA and
  88 /// ResourceB only have one bit set.
  89 /// ResourceAB is a group; excluding the most significant bit in the mask, the
  90 /// remaining bits identify the composition of the group.
  91 ///
  92 /// Resource masks are used by the ResourceManager to solve set membership
  93 /// problems with simple bit manipulation operations.
  94 void computeProcResourceMasks(const MCSchedModel &SM,
  95                               MutableArrayRef<uint64_t> Masks);
  96
  97 // Returns the index of the highest bit set. For resource masks, the position of
  98 // the highest bit set can be used to construct a resource mask identifier.
  99 inline unsigned getResourceStateIndex(uint64_t Mask) {
 100   assert(Mask && "Processor Resource Mask cannot be zero!");
 101   return (std::numeric_limits<uint64_t>::digits - countLeadingZeros(Mask)) - 1;
 102 }
 103
 104 /// Compute the reciprocal block throughput from a set of processor resource
 105 /// cycles. The reciprocal block throughput is computed as the MAX between:
 106 ///  - NumMicroOps / DispatchWidth
 107 ///  - ProcResourceCycles / #ProcResourceUnits  (for every consumed resource).
 108 double computeBlockRThroughput(const MCSchedModel &SM, unsigned DispatchWidth,
 109                                unsigned NumMicroOps,
 110                                ArrayRef<unsigned> ProcResourceUsage);
 111 } // namespace mca
 112 } // namespace llvm
 113
 114 #endif // LLVM_MCA_SUPPORT_H