fpc.cc

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#include "mem/cache/compressors/fpc.hh"
 
#include "mem/cache/compressors/dictionary_compressor_impl.hh"
#include "params/FPC.hh"
 
namespace Compressor {
 
FPC::FPCCompData::FPCCompData(int zero_run_size_bits)
  : CompData(), zeroRunSizeBits(zero_run_size_bits)
{
}
 
void
FPC::FPCCompData::addEntry(std::unique_ptr<Pattern> pattern)
{
    // If this is a zero match, check for zero runs
    if (pattern->getPatternNumber() == ZERO_RUN) {
        // If it is a new zero run, create it; otherwise, increase current
        // run's length
        if (!entries.size() ||
            (entries.back()->getPatternNumber() != ZERO_RUN)) {
            static_cast<ZeroRun*>(pattern.get())->setRealSize(zeroRunSizeBits);
        } else {
            // A zero run has a maximum length, given by the number of bits
            // used to represent it. When this limit is reached, a new run
            // must be created
            const int run_length =
                static_cast<ZeroRun*>(entries.back().get())->getRunLength();
            if (run_length == mask(zeroRunSizeBits)) {
                // The limit for this zero run has been reached, so a new
                // run must be started, with a sized pattern
                static_cast<ZeroRun*>(pattern.get())->setRealSize(
                    zeroRunSizeBits);
            } else {
                // Increase the current run's length.
                // Since the first zero entry of the run contains the size,
                // and all the following ones are created just to simplify
                // decompression, this fake pattern will have a size of 0 bits
                static_cast<ZeroRun*>(pattern.get())->setRunLength(
                    run_length + 1);
            }
        }
    }
 
    CompData::addEntry(std::move(pattern));
}
 
FPC::FPC(const Params &p)
  : DictionaryCompressor<uint32_t>(p), zeroRunSizeBits(p.zero_run_bits)
{
}
 
void
FPC::addToDictionary(const DictionaryEntry data)
{
    // There is no dictionary in FPC, so its size is zero, and no pattern
    // causes an insertion in the dictionary. The only reason we do not
    // assert it is that the UncompressedPattern implementation always
    // inserts by default
}
 
std::unique_ptr<DictionaryCompressor<uint32_t>::CompData>
FPC::instantiateDictionaryCompData() const
{
    return std::unique_ptr<DictionaryCompressor<uint32_t>::CompData>(
        new FPCCompData(zeroRunSizeBits));
}
 
} // namespace Compressor