SIMD-accelerate JSON string scanning in JSONLexer#1984
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lavenzg wants to merge 1 commit intofacebook:static_hfrom
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SIMD-accelerate JSON string scanning in JSONLexer#1984lavenzg wants to merge 1 commit intofacebook:static_hfrom
lavenzg wants to merge 1 commit intofacebook:static_hfrom
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Summary: Add SIMD-optimized character scanning functions (scanSpecialCharU8, scanSpecialCharU16) that find the first byte/char16_t that is '"', '\\', or <= 0x1F. Use these in JSONLexer::scanString() to skip over runs of normal characters in bulk during the escape-free hot loop. The SIMD scan applies only to ASCII and UTF16 encodings (where UsesRawPtr is true and we have a contiguous buffer with known bounds). UTF8 uses UTF16Stream which is not a raw pointer and is unaffected. Jenkins hash is handled separately: after SIMD skips a range of normal characters, the hash is computed over that range in a scalar loop, keeping the SIMD scan free of data dependencies. Implementation tiers: - NEON (aarch64): 16 bytes / 8 char16_t per iteration - SSE2 (x86-64): 16 bytes / 8 char16_t per iteration - Scalar fallback for all other platforms Differential Revision: D93549305
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Summary:
Add SIMD-optimized character scanning functions (scanSpecialCharU8, scanSpecialCharU16) that find the first byte/char16_t that is '"', '\', or <= 0x1F. Use these in JSONLexer::scanString() to skip over runs of normal characters in bulk during the escape-free hot loop.
The SIMD scan applies only to ASCII and UTF16 encodings (where UsesRawPtr is true and we have a contiguous buffer with known bounds). UTF8 uses UTF16Stream which is not a raw pointer and is unaffected.
Jenkins hash is handled separately: after SIMD skips a range of normal characters, the hash is computed over that range in a scalar loop, keeping the SIMD scan free of data dependencies.
Implementation tiers:
Differential Revision: D93549305