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Merge pull request #95 from szabadka/master
Decoder optimizations for ARM architecture.
This commit is contained in:
szabadka
commit
762f9ba5a0
@ -30,6 +30,11 @@ extern "C" {
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#if (defined(__x86_64__) || defined(_M_X64))
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/* This should be set to 1 only on little-endian machines. */
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#define BROTLI_USE_64_BITS 1
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#elif (defined(__arm__))
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/* TODO: __arm__ is much too broad. The following flags should
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only be set on ARM architectures with little-endian byte order */
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#define ARMv7
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#define BROTLI_USE_64_BITS 1
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#else
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#define BROTLI_USE_64_BITS 0
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#endif
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@ -41,10 +46,16 @@ extern "C" {
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#define UNALIGNED_COPY64(dst, src) memcpy(dst, src, 8)
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#define UNALIGNED_MOVE64(dst, src) memmove(dst, src, 8)
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#ifdef ARMv7
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/* Arm instructions can shift and negate registers before an AND operation. */
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static BROTLI_INLINE uint32_t BitMask(int n) { return ~((0xffffffff) << n); }
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#else
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static const uint32_t kBitMask[BROTLI_MAX_NUM_BIT_READ] = {
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0, 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767,
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65535, 131071, 262143, 524287, 1048575, 2097151, 4194303, 8388607, 16777215
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};
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static BROTLI_INLINE uint32_t BitMask(int n) { return kBitMask[n]; }
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#endif
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typedef struct {
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#if (BROTLI_USE_64_BITS)
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@ -91,7 +102,7 @@ static BROTLI_INLINE void BrotliSetBitPos(BrotliBitReader* const br,
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uint32_t val) {
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#ifdef BROTLI_DECODE_DEBUG
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uint32_t n_bits = val - br->bit_pos_;
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const uint32_t bval = (uint32_t)(br->val_ >> br->bit_pos_) & kBitMask[n_bits];
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const uint32_t bval = (uint32_t)(br->val_ >> br->bit_pos_) & BitMask(n_bits);
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printf("[BrotliReadBits] %010d %2d val: %6x\n",
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(br->pos_ << 3) + br->bit_pos_ - 64, n_bits, bval);
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#endif
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@ -148,7 +159,7 @@ static BROTLI_INLINE int BrotliReadMoreInput(BrotliBitReader* const br) {
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}
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br->eos_ = 1;
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/* Store 32 bytes of zero after the stream end. */
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#if (BROTLI_USE_64_BITS)
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#if (BROTLI_USE_64_BITS) && !defined(ARMv7)
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*(uint64_t*)(dst + bytes_read) = 0;
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*(uint64_t*)(dst + bytes_read + 8) = 0;
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*(uint64_t*)(dst + bytes_read + 16) = 0;
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@ -159,7 +170,7 @@ static BROTLI_INLINE int BrotliReadMoreInput(BrotliBitReader* const br) {
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}
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if (dst == br->buf_) {
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/* Copy the head of the ringbuffer to the slack region. */
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#if (BROTLI_USE_64_BITS)
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#if (BROTLI_USE_64_BITS) && !defined(ARMv7)
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UNALIGNED_COPY64(br->buf_ + BROTLI_IBUF_SIZE - 32, br->buf_);
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UNALIGNED_COPY64(br->buf_ + BROTLI_IBUF_SIZE - 24, br->buf_ + 8);
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UNALIGNED_COPY64(br->buf_ + BROTLI_IBUF_SIZE - 16, br->buf_ + 16);
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@ -203,8 +214,15 @@ static BROTLI_INLINE uint32_t BrotliReadBits(
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BrotliBitReader* const br, int n_bits) {
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uint32_t val;
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#if (BROTLI_USE_64_BITS)
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#if defined(ARMv7)
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if ((64 - br->bit_pos_) < ((uint32_t) n_bits)) {
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BrotliFillBitWindow(br);
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}
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val = (uint32_t)(br->val_ >> br->bit_pos_) & BitMask(n_bits);
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#else
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BrotliFillBitWindow(br);
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val = (uint32_t)(br->val_ >> br->bit_pos_) & kBitMask[n_bits];
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val = (uint32_t)(br->val_ >> br->bit_pos_) & BitMask(n_bits);
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#endif /* defined (ARMv7) */
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#else
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/*
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* The if statement gives 2-4% speed boost on Canterbury data set with
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@ -213,8 +231,8 @@ static BROTLI_INLINE uint32_t BrotliReadBits(
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if ((32 - br->bit_pos_) < ((uint32_t) n_bits)) {
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BrotliFillBitWindow(br);
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}
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val = (br->val_ >> br->bit_pos_) & kBitMask[n_bits];
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#endif
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val = (br->val_ >> br->bit_pos_) & Bitmask(n_bits);
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#endif /* BROTLI_USE_64_BITS */
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#ifdef BROTLI_DECODE_DEBUG
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printf("[BrotliReadBits] %010d %2d val: %6x\n",
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(br->pos_ << 3) + br->bit_pos_ - 64, n_bits, val);
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33
dec/decode.c
33
dec/decode.c
@ -149,6 +149,21 @@ static BROTLI_INLINE int ReadSymbol(const HuffmanCode* table,
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BrotliBitReader* br) {
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int nbits;
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BrotliFillBitWindow(br);
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#ifdef ARMv7
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/* Prefetching helps, since this needs to shift a 64 bit
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val by a variable length. The other changes are minor. */
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uint32_t val = BrotliPrefetchBits(br);
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table += val & HUFFMAN_TABLE_MASK;
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nbits = table->bits;
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if (PREDICT_FALSE(nbits > HUFFMAN_TABLE_BITS)) {
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nbits -= HUFFMAN_TABLE_BITS;
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br->bit_pos_ += HUFFMAN_TABLE_BITS;
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table += table->value;
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table += (int)(val >> HUFFMAN_TABLE_BITS) & ((1 << nbits) - 1);
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nbits = table->bits;
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}
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br->bit_pos_ += nbits;
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#else
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table += (int)(br->val_ >> br->bit_pos_) & HUFFMAN_TABLE_MASK;
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if (PREDICT_FALSE(table->bits > HUFFMAN_TABLE_BITS)) {
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br->bit_pos_ += HUFFMAN_TABLE_BITS;
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@ -157,6 +172,7 @@ static BROTLI_INLINE int ReadSymbol(const HuffmanCode* table,
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table += (int)(br->val_ >> br->bit_pos_) & ((1 << nbits) - 1);
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}
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br->bit_pos_ += table->bits;
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#endif
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return table->value;
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}
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@ -624,6 +640,8 @@ static BROTLI_INLINE void DecodeBlockTypeWithContext(BrotliState* s,
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*/
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static BROTLI_INLINE void IncrementalCopyFastPath(
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uint8_t* dst, const uint8_t* src, int len) {
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/* TODO: On an ARM UNALIGNED_MOVE64 is compiled into a memcpy.
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But I don't have a better solution. */
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if (src < dst) {
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while (dst - src < 8) {
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UNALIGNED_MOVE64(dst, src);
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@ -1488,6 +1506,7 @@ BrotliResult BrotliDecompressStreaming(BrotliInput input, BrotliOutput output,
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s->copy_src =
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&s->ringbuffer[(pos - s->distance) & s->ringbuffer_mask];
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#if (defined(__x86_64__) || defined(_M_X64))
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if (s->copy_src + s->copy_length <= s->ringbuffer_end &&
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s->copy_dst + s->copy_length < s->ringbuffer_end) {
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@ -1501,6 +1520,20 @@ BrotliResult BrotliDecompressStreaming(BrotliInput input, BrotliOutput output,
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s->meta_block_remaining_len -= s->copy_length;
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s->copy_length = 0;
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}
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#elif defined(ARMv7)
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/* This version is maybe 5% faster than the version above.
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UNALIGNED_COPY64 does not inline and generates memcpy calls. */
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if (s->copy_src + s->copy_length <= s->ringbuffer_end &&
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s->copy_dst + s->copy_length < s->ringbuffer_end) {
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if (s->copy_length <= s->distance) {
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memcpy(s->copy_dst, s->copy_src, s->copy_length);
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} else {
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IncrementalCopyFastPath(s->copy_dst, s->copy_src, s->copy_length);
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}
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pos += s->copy_length;
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s->meta_block_remaining_len -= s->copy_length;
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s->copy_length = 0;
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}
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#endif
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/* Modifications to this loop shold be reflected in
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BROTLI_STATE_BLOCK_POST_WRITE_2 case */
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