Move SSE2 bit reader functionality out into a class.

diff --git a/turbopfor.h b/turbopfor.h
index ddcdec830f6efe18ca44ec62ac2edab740862509..f58968701e0ff7714ec5f1a09dd1ea32963521b3 100644 (file)
--- a/turbopfor.h
+++ b/turbopfor.h
@@ -160,6 +160,33 @@ private:
        unsigned bits_used = 0;
 };
 
+#ifdef COULD_HAVE_SSE2
+struct InterleavedBitReaderSSE2 {
+public:
+       InterleavedBitReaderSSE2(const unsigned char *in, unsigned bits)
+               : in(reinterpret_cast<const __m128i *>(in)), bits(bits), mask(_mm_set1_epi32((1U << bits) - 1)) {}
+       __m128i read() {
+               __m128i val = _mm_srli_epi32(_mm_loadu_si128(in), bits_used);
+               if (bits_used + bits > 32) {
+                       __m128i val_upper = _mm_slli_epi32(_mm_loadu_si128(in + 1), 32 - bits_used);
+                       val = _mm_or_si128(val, val_upper);
+               }
+               val = _mm_and_si128(val, mask);
+
+               bits_used += bits;
+               in += bits_used / 32;
+               bits_used %= 32;
+               return val;
+       }
+
+private:
+       const __m128i *in;
+       const unsigned bits;
+       const __m128i mask;
+       unsigned bits_used = 0;
+};
+#endif
+
 // Does not properly account for overflow.
 inline unsigned div_round_up(unsigned val, unsigned div)
 {
@@ -244,18 +271,11 @@ template<unsigned BlockSize, bool OrWithExisting, bool DeltaDecode>
 __attribute__((target("sse2")))
 const unsigned char *decode_bitmap_sse2(const unsigned char *in, unsigned bit_width, uint32_t *out)
 {
-       const __m128i *invec = reinterpret_cast<const __m128i *>(in);
        __m128i *outvec = reinterpret_cast<__m128i *>(out);
-       const __m128i mask = _mm_set1_epi32((1U << bit_width) - 1);
-       unsigned bits_used = 0;
        DeltaDecoderSSE2 delta(out[-1]);
+       InterleavedBitReaderSSE2 bs(in, bit_width);
        for (unsigned i = 0; i < BlockSize / 4; ++i) {
-               __m128i val = _mm_srli_epi32(_mm_loadu_si128(invec), bits_used);
-               if (bits_used + bit_width > 32) {
-                       __m128i val_upper = _mm_slli_epi32(_mm_loadu_si128(invec + 1), 32 - bits_used);
-                       val = _mm_or_si128(val, val_upper);
-               }
-               val = _mm_and_si128(val, mask);
+               __m128i val = bs.read();
                if constexpr (OrWithExisting) {
                        val = _mm_or_si128(val, _mm_loadu_si128(outvec + i));
                }
@@ -263,10 +283,6 @@ const unsigned char *decode_bitmap_sse2(const unsigned char *in, unsigned bit_wi
                        val = delta.decode(val);
                }
                _mm_storeu_si128(outvec + i, val);
-
-               bits_used += bit_width;
-               invec += bits_used / 32;
-               bits_used %= 32;
        }
        in += bytes_for_packed_bits(BlockSize, bit_width);
        return in;