liblzma: CRC64 CLMUL: Refactor the constants

Now it refers to crc_clmul_consts_gen.c. vfold8 was renamed to mu_p
and the p no longer has the lowest bit set (it makes no difference
as the output bits it affects are ignored).

diff --git a/src/liblzma/check/crc_x86_clmul.h b/src/liblzma/check/crc_x86_clmul.h
index 90da2c0692c2c349d512433ed71028c34d1a3406..7dd84fbe79c717f2141def2ab2bc856515a0a9a8 100644 (file)
--- a/src/liblzma/check/crc_x86_clmul.h
+++ b/src/liblzma/check/crc_x86_clmul.h
@@ -280,33 +280,6 @@ crc32_arch_optimized(const uint8_t *buf, size_t size, uint32_t crc)
 // x86 CLMUL CRC64 //
 /////////////////////
 
-/*
-// These functions were used to generate the constants
-// at the top of crc64_arch_optimized().
-static uint64_t
-calc_lo(uint64_t poly)
-{
-       uint64_t a = poly;
-       uint64_t b = 0;
-
-       for (unsigned i = 0; i < 64; ++i) {
-               b = (b >> 1) | (a << 63);
-               a = (a >> 1) ^ (a & 1 ? poly : 0);
-       }
-
-       return b;
-}
-
-static uint64_t
-calc_hi(uint64_t poly, uint64_t a)
-{
-       for (unsigned i = 0; i < 64; ++i)
-               a = (a >> 1) ^ (a & 1 ? poly : 0);
-
-       return a;
-}
-*/
-
 #ifdef BUILDING_CRC64_CLMUL
 
 // MSVC (VS2015 - VS2022) produces bad 32-bit x86 code from the CLMUL CRC
@@ -333,14 +306,12 @@ crc64_arch_optimized(const uint8_t *buf, size_t size, uint64_t crc)
        if (size == 0)
                return crc;
 
-       // const uint64_t poly = 0xc96c5795d7870f42; // CRC polynomial
-       const uint64_t p  = 0x92d8af2baf0e1e85; // (poly << 1) | 1
-       const uint64_t mu = 0x9c3e466c172963d5; // (calc_lo(poly) << 1) | 1
-       const uint64_t k2 = 0xdabe95afc7875f40; // calc_hi(poly, 1)
-       const uint64_t k1 = 0xe05dd497ca393ae4; // calc_hi(poly, k2)
+       // See crc_clmul_consts_gen.c.
+       const __m128i vfold16 = _mm_set_epi64x(
+               (int64_t)0xdabe95afc7875f40, (int64_t)0xe05dd497ca393ae4);
 
-       const __m128i vfold8 = _mm_set_epi64x((int64_t)p, (int64_t)mu);
-       const __m128i vfold16 = _mm_set_epi64x((int64_t)k2, (int64_t)k1);
+       const __m128i mu_p = _mm_set_epi64x(
+               (int64_t)0x9c3e466c172963d5, (int64_t)0x92d8af2baf0e1e84);
 
        __m128i v0, v1, v2;
 
@@ -355,8 +326,8 @@ crc64_arch_optimized(const uint8_t *buf, size_t size, uint64_t crc)
 #endif
 
        v1 = _mm_xor_si128(_mm_clmulepi64_si128(v0, vfold16, 0x10), v1);
-       v0 = _mm_clmulepi64_si128(v1, vfold8, 0x00);
-       v2 = _mm_clmulepi64_si128(v0, vfold8, 0x10);
+       v0 = _mm_clmulepi64_si128(v1, mu_p, 0x10);
+       v2 = _mm_clmulepi64_si128(v0, mu_p, 0x00);
        v0 = _mm_xor_si128(_mm_xor_si128(v1, _mm_slli_si128(v0, 8)), v2);
 
 #if defined(__i386__) || defined(_M_IX86)