| //===--------------------- Support.cpp --------------------------*- 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 |
| // |
| //===----------------------------------------------------------------------===// |
| /// \file |
| /// |
| /// This file implements a few helper functions used by various pipeline |
| /// components. |
| /// |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/MCA/Support.h" |
| #include "llvm/MC/MCSchedule.h" |
| #include <numeric> |
| |
| namespace llvm { |
| namespace mca { |
| |
| #define DEBUG_TYPE "llvm-mca" |
| |
| ReleaseAtCycles &ReleaseAtCycles::operator+=(const ReleaseAtCycles &RHS) { |
| if (Denominator == RHS.Denominator) |
| Numerator += RHS.Numerator; |
| else { |
| // Create a common denominator for LHS and RHS by calculating the least |
| // common multiple from the GCD. |
| unsigned GCD = std::gcd(Denominator, RHS.Denominator); |
| unsigned LCM = (Denominator * RHS.Denominator) / GCD; |
| unsigned LHSNumerator = Numerator * (LCM / Denominator); |
| unsigned RHSNumerator = RHS.Numerator * (LCM / RHS.Denominator); |
| Numerator = LHSNumerator + RHSNumerator; |
| Denominator = LCM; |
| } |
| return *this; |
| } |
| |
| void computeProcResourceMasks(const MCSchedModel &SM, |
| MutableArrayRef<uint64_t> Masks) { |
| unsigned ProcResourceID = 0; |
| |
| assert(Masks.size() == SM.getNumProcResourceKinds() && |
| "Invalid number of elements"); |
| // Resource at index 0 is the 'InvalidUnit'. Set an invalid mask for it. |
| Masks[0] = 0; |
| |
| // Create a unique bitmask for every processor resource unit. |
| for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) { |
| const MCProcResourceDesc &Desc = *SM.getProcResource(I); |
| if (Desc.SubUnitsIdxBegin) |
| continue; |
| Masks[I] = 1ULL << ProcResourceID; |
| ProcResourceID++; |
| } |
| |
| // Create a unique bitmask for every processor resource group. |
| for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) { |
| const MCProcResourceDesc &Desc = *SM.getProcResource(I); |
| if (!Desc.SubUnitsIdxBegin) |
| continue; |
| Masks[I] = 1ULL << ProcResourceID; |
| for (unsigned U = 0; U < Desc.NumUnits; ++U) { |
| uint64_t OtherMask = Masks[Desc.SubUnitsIdxBegin[U]]; |
| Masks[I] |= OtherMask; |
| } |
| ProcResourceID++; |
| } |
| |
| #ifndef NDEBUG |
| LLVM_DEBUG(dbgs() << "\nProcessor resource masks:" |
| << "\n"); |
| for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) { |
| const MCProcResourceDesc &Desc = *SM.getProcResource(I); |
| LLVM_DEBUG(dbgs() << '[' << format_decimal(I,2) << "] " << " - " |
| << format_hex(Masks[I],16) << " - " |
| << Desc.Name << '\n'); |
| } |
| #endif |
| } |
| |
| double computeBlockRThroughput(const MCSchedModel &SM, unsigned DispatchWidth, |
| unsigned NumMicroOps, |
| ArrayRef<unsigned> ProcResourceUsage) { |
| // The block throughput is bounded from above by the hardware dispatch |
| // throughput. That is because the DispatchWidth is an upper bound on the |
| // number of opcodes that can be part of a single dispatch group. |
| double Max = static_cast<double>(NumMicroOps) / DispatchWidth; |
| |
| // The block throughput is also limited by the amount of hardware parallelism. |
| // The number of available resource units affects the resource pressure |
| // distribution, as well as how many blocks can be executed every cycle. |
| for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) { |
| unsigned ReleaseAtCycles = ProcResourceUsage[I]; |
| if (!ReleaseAtCycles) |
| continue; |
| |
| const MCProcResourceDesc &MCDesc = *SM.getProcResource(I); |
| double Throughput = static_cast<double>(ReleaseAtCycles) / MCDesc.NumUnits; |
| Max = std::max(Max, Throughput); |
| } |
| |
| // The block reciprocal throughput is computed as the MAX of: |
| // - (NumMicroOps / DispatchWidth) |
| // - (NumUnits / ReleaseAtCycles) for every consumed processor resource. |
| return Max; |
| } |
| |
| } // namespace mca |
| } // namespace llvm |