mirror of
https://github.com/simdjson/simdjson
synced 2026-06-08 17:27:07 +00:00
John Keiser
47 lines
1.4 KiB
C++
47 lines
1.4 KiB
C++
#ifndef SIMDJSON_PPC64_BITMASK_H
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#define SIMDJSON_PPC64_BITMASK_H
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#ifndef SIMDJSON_CONDITIONAL_INCLUDE
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#include "simdjson/ppc64/base.h"
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#endif // SIMDJSON_CONDITIONAL_INCLUDE
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namespace simdjson {
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namespace ppc64 {
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namespace {
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//
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// Perform a "cumulative bitwise xor," flipping bits each time a 1 is
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// encountered.
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//
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// For example, prefix_xor(00100100) == 00011100
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//
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simdjson_inline uint64_t prefix_xor(uint64_t bitmask) {
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// You can use the version below, however gcc sometimes miscompiles
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// vec_pmsum_be, it happens somewhere around between 8 and 9th version.
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// The performance boost was not noticeable, falling back to a usual
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// implementation.
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// __vector unsigned long long all_ones = {~0ull, ~0ull};
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// __vector unsigned long long mask = {bitmask, 0};
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// // Clang and GCC return different values for pmsum for ull so cast it to one.
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// // Generally it is not specified by ALTIVEC ISA what is returned by
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// // vec_pmsum_be.
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// #if defined(__LITTLE_ENDIAN__)
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// return (uint64_t)(((__vector unsigned long long)vec_pmsum_be(all_ones, mask))[0]);
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// #else
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// return (uint64_t)(((__vector unsigned long long)vec_pmsum_be(all_ones, mask))[1]);
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// #endif
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bitmask ^= bitmask << 1;
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bitmask ^= bitmask << 2;
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bitmask ^= bitmask << 4;
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bitmask ^= bitmask << 8;
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bitmask ^= bitmask << 16;
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bitmask ^= bitmask << 32;
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return bitmask;
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}
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} // unnamed namespace
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} // namespace ppc64
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} // namespace simdjson
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#endif
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