1 //===--------------------- Support.cpp --------------------------*- 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 /// This file implements a few helper functions used by various pipeline 11 /// components. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #include "llvm/MCA/Support.h" 16 #include "llvm/MC/MCSchedule.h" 17 18 namespace llvm { 19 namespace mca { 20 21 #define DEBUG_TYPE "llvm-mca" 22 23 ResourceCycles &ResourceCycles::operator+=(const ResourceCycles &RHS) { 24 if (Denominator == RHS.Denominator) 25 Numerator += RHS.Numerator; 26 else { 27 // Create a common denominator for LHS and RHS by calculating the least 28 // common multiple from the GCD. 29 unsigned GCD = GreatestCommonDivisor64(Denominator, RHS.Denominator); 30 unsigned LCM = (Denominator * RHS.Denominator) / GCD; 31 unsigned LHSNumerator = Numerator * (LCM / Denominator); 32 unsigned RHSNumerator = RHS.Numerator * (LCM / RHS.Denominator); 33 Numerator = LHSNumerator + RHSNumerator; 34 Denominator = LCM; 35 } 36 return *this; 37 } 38 39 void computeProcResourceMasks(const MCSchedModel &SM, 40 MutableArrayRef<uint64_t> Masks) { 41 unsigned ProcResourceID = 0; 42 43 assert(Masks.size() == SM.getNumProcResourceKinds() && 44 "Invalid number of elements"); 45 // Resource at index 0 is the 'InvalidUnit'. Set an invalid mask for it. 46 Masks[0] = 0; 47 48 // Create a unique bitmask for every processor resource unit. 49 for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) { 50 const MCProcResourceDesc &Desc = *SM.getProcResource(I); 51 if (Desc.SubUnitsIdxBegin) 52 continue; 53 Masks[I] = 1ULL << ProcResourceID; 54 ProcResourceID++; 55 } 56 57 // Create a unique bitmask for every processor resource group. 58 for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) { 59 const MCProcResourceDesc &Desc = *SM.getProcResource(I); 60 if (!Desc.SubUnitsIdxBegin) 61 continue; 62 Masks[I] = 1ULL << ProcResourceID; 63 for (unsigned U = 0; U < Desc.NumUnits; ++U) { 64 uint64_t OtherMask = Masks[Desc.SubUnitsIdxBegin[U]]; 65 Masks[I] |= OtherMask; 66 } 67 ProcResourceID++; 68 } 69 70 #ifndef NDEBUG 71 LLVM_DEBUG(dbgs() << "\nProcessor resource masks:" 72 << "\n"); 73 for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) { 74 const MCProcResourceDesc &Desc = *SM.getProcResource(I); 75 LLVM_DEBUG(dbgs() << '[' << format_decimal(I,2) << "] " << " - " 76 << format_hex(Masks[I],16) << " - " 77 << Desc.Name << '\n'); 78 } 79 #endif 80 } 81 82 double computeBlockRThroughput(const MCSchedModel &SM, unsigned DispatchWidth, 83 unsigned NumMicroOps, 84 ArrayRef<unsigned> ProcResourceUsage) { 85 // The block throughput is bounded from above by the hardware dispatch 86 // throughput. That is because the DispatchWidth is an upper bound on the 87 // number of opcodes that can be part of a single dispatch group. 88 double Max = static_cast<double>(NumMicroOps) / DispatchWidth; 89 90 // The block throughput is also limited by the amount of hardware parallelism. 91 // The number of available resource units affects the resource pressure 92 // distribution, as well as how many blocks can be executed every cycle. 93 for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) { 94 unsigned ResourceCycles = ProcResourceUsage[I]; 95 if (!ResourceCycles) 96 continue; 97 98 const MCProcResourceDesc &MCDesc = *SM.getProcResource(I); 99 double Throughput = static_cast<double>(ResourceCycles) / MCDesc.NumUnits; 100 Max = std::max(Max, Throughput); 101 } 102 103 // The block reciprocal throughput is computed as the MAX of: 104 // - (NumMicroOps / DispatchWidth) 105 // - (NumUnits / ResourceCycles) for every consumed processor resource. 106 return Max; 107 } 108 109 } // namespace mca 110 } // namespace llvm 111