85e3875ad7
D150312 added a TODO: TODO: consider renaming the field `StartAtCycle` and `Cycles` to `AcquireAtCycle` and `ReleaseAtCycle` respectively, to stress the fact that resource allocation is now represented as an interval, relatively to the issue cycle of the instruction. This patch implements that TODO. This naming clarifies how to use these fields in the scheduler. In addition it was confusing that `StartAtCycle` was singular but `Cycles` was plural. This renaming fixes this inconsistency. This commit as previously reverted since it missed renaming that came down after rebasing. This version of the commit fixes those problems. Differential Revision: https://reviews.llvm.org/D158568
112 lines
4.0 KiB
C++
112 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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#include <numeric>
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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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ReleaseAtCycles &ReleaseAtCycles::operator+=(const ReleaseAtCycles &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 = std::gcd(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 ReleaseAtCycles = ProcResourceUsage[I];
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if (!ReleaseAtCycles)
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continue;
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const MCProcResourceDesc &MCDesc = *SM.getProcResource(I);
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double Throughput = static_cast<double>(ReleaseAtCycles) / 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 / ReleaseAtCycles) 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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