111 lines
4.0 KiB
C++
111 lines
4.0 KiB
C++
//===--------------------- Support.cpp --------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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/// \file
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///
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/// This file implements a few helper functions used by various pipeline
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/// components.
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///
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//===----------------------------------------------------------------------===//
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#include "llvm/MCA/Support.h"
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#include "llvm/MC/MCSchedule.h"
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namespace llvm {
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namespace mca {
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#define DEBUG_TYPE "llvm-mca"
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ResourceCycles &ResourceCycles::operator+=(const ResourceCycles &RHS) {
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if (Denominator == RHS.Denominator)
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Numerator += RHS.Numerator;
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else {
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// Create a common denominator for LHS and RHS by calculating the least
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// common multiple from the GCD.
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unsigned GCD = GreatestCommonDivisor64(Denominator, RHS.Denominator);
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unsigned LCM = (Denominator * RHS.Denominator) / GCD;
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unsigned LHSNumerator = Numerator * (LCM / Denominator);
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unsigned RHSNumerator = RHS.Numerator * (LCM / RHS.Denominator);
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Numerator = LHSNumerator + RHSNumerator;
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Denominator = LCM;
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}
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return *this;
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}
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void computeProcResourceMasks(const MCSchedModel &SM,
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MutableArrayRef<uint64_t> Masks) {
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unsigned ProcResourceID = 0;
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assert(Masks.size() == SM.getNumProcResourceKinds() &&
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"Invalid number of elements");
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// Resource at index 0 is the 'InvalidUnit'. Set an invalid mask for it.
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Masks[0] = 0;
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// Create a unique bitmask for every processor resource unit.
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for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
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const MCProcResourceDesc &Desc = *SM.getProcResource(I);
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if (Desc.SubUnitsIdxBegin)
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continue;
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Masks[I] = 1ULL << ProcResourceID;
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ProcResourceID++;
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}
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// Create a unique bitmask for every processor resource group.
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for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
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const MCProcResourceDesc &Desc = *SM.getProcResource(I);
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if (!Desc.SubUnitsIdxBegin)
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continue;
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Masks[I] = 1ULL << ProcResourceID;
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for (unsigned U = 0; U < Desc.NumUnits; ++U) {
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uint64_t OtherMask = Masks[Desc.SubUnitsIdxBegin[U]];
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Masks[I] |= OtherMask;
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}
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ProcResourceID++;
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}
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#ifndef NDEBUG
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LLVM_DEBUG(dbgs() << "\nProcessor resource masks:"
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<< "\n");
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for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
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const MCProcResourceDesc &Desc = *SM.getProcResource(I);
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LLVM_DEBUG(dbgs() << '[' << format_decimal(I,2) << "] " << " - "
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<< format_hex(Masks[I],16) << " - "
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<< Desc.Name << '\n');
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}
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#endif
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}
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double computeBlockRThroughput(const MCSchedModel &SM, unsigned DispatchWidth,
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unsigned NumMicroOps,
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ArrayRef<unsigned> ProcResourceUsage) {
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// The block throughput is bounded from above by the hardware dispatch
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// throughput. That is because the DispatchWidth is an upper bound on the
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// number of opcodes that can be part of a single dispatch group.
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double Max = static_cast<double>(NumMicroOps) / DispatchWidth;
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// The block throughput is also limited by the amount of hardware parallelism.
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// The number of available resource units affects the resource pressure
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// distribution, as well as how many blocks can be executed every cycle.
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for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
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unsigned ResourceCycles = ProcResourceUsage[I];
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if (!ResourceCycles)
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continue;
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const MCProcResourceDesc &MCDesc = *SM.getProcResource(I);
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double Throughput = static_cast<double>(ResourceCycles) / MCDesc.NumUnits;
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Max = std::max(Max, Throughput);
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}
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// The block reciprocal throughput is computed as the MAX of:
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// - (NumMicroOps / DispatchWidth)
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// - (NumUnits / ResourceCycles) for every consumed processor resource.
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return Max;
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}
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} // namespace mca
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} // namespace llvm
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