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Use SSE2 on x86-64 without checking at runtime #1116

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Merged
byroot merged 2 commits into from
Oct 15, 2026
+4 −15
Merged

Use SSE2 on x86-64 without checking at runtime #1116

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bf5bf9a
json: Use SSE2 on x86-64 without checking at runtime
hsbt Oct 13, 2026
93e6873
Drop the leftovers of runtime SSE2 detection
hsbt Oct 15, 2026
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7 changes: 2 additions & 5 deletions ext/json/ext/simd/conf.rb
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Original file line number Diff line number Diff line change
@@ -1,16 +1,15 @@
case RbConfig::CONFIG['host_cpu']
when /^(arm|aarch64)/
# Try to compile a small program using NEON instructions
header, type, init, extra = 'arm_neon.h', 'uint8x16_t', 'vdupq_n_u8(32)', nil
header, type, init = 'arm_neon.h', 'uint8x16_t', 'vdupq_n_u8(32)'
when /^(x86_64|x64)/
header, type, init, extra = 'x86intrin.h', '__m128i', '_mm_set1_epi8(32)', 'if (__builtin_cpu_supports("sse2")) { printf("OK"); }'
header, type, init = 'x86intrin.h', '__m128i', '_mm_set1_epi8(32)'
end
if header
if have_header(header) && try_compile(<<~SRC, '-Werror=implicit-function-declaration')
#{cpp_include(header)}
int main(int argc, char **argv) {
#{type} test = #{init};
#{extra}
if (argc > 100000) printf("%p", &test);
return 0;
}
Expand All @@ -20,5 +19,3 @@
puts "Disable SIMD"
end
end

have_header('cpuid.h')
12 changes: 2 additions & 10 deletions ext/json/ext/simd/simd.h
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Expand Up @@ -143,7 +143,6 @@ ALWAYS_INLINE(static) int string_scan_simd_neon(const char **ptr, const char *en
#define HAVE_SIMD 1
#define HAVE_SIMD_SSE2 1

#ifdef HAVE_CPUID_H
#define FIND_SIMD_IMPLEMENTATION_DEFINED 1

#if defined(__clang__) || defined(__GNUC__)
Expand Down Expand Up @@ -182,17 +181,10 @@ ALWAYS_INLINE(static) TARGET_SSE2 int string_scan_simd_sse2(const char **ptr, co
return 0;
}

#include <cpuid.h>
#endif /* HAVE_CPUID_H */

static inline SIMD_Implementation find_simd_implementation(void)
{
// TODO Revisit. I think the SSE version now only uses SSE2 instructions.
if (__builtin_cpu_supports("sse2")) {
return SIMD_SSE2;
}

return SIMD_NONE;
// SSE2 is part of the x86-64 baseline.
return SIMD_SSE2;
}

#endif /* HAVE_X86INTRIN_H */
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