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Commite2809e3

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Inline CRC computation for small fixed-length input on x86
pg_crc32c.h now has a simplified copy of the loop in pg_crc32c_sse42.csuitable for inlining where possible.This may slightly reduce contention for the WAL insertion lock,but that hasn't been tested. The motivation for this change is avoidregressing for a future commit that will use a function pointer fornon-constant input in all x86 builds.While it's technically possible to make a similar change for Arm andLoongArch, there are some questions about how inlining should worksince those platforms prefer stricter alignment. There are also noimmediate plans to add additional implementations for them.Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>Reviewed-by: Raghuveer Devulapalli <raghuveer.devulapalli@intel.com>Discussion:https://postgr.es/m/CANWCAZZEiTzhZcuwTiJ2=opiNpAUn1vuDRu1N02z61AthwRZLA@mail.gmail.comDiscussion:https://postgr.es/m/CANWCAZYRhLHArpyfV4uRK-Rw9N5oV5HMkkKtBehcuTjNOMwCZg@mail.gmail.com
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‎src/include/port/pg_crc32c.h

Lines changed: 31 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -43,12 +43,42 @@ typedef uint32 pg_crc32c;
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#if defined(USE_SSE42_CRC32C)
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/* Use Intel SSE4.2 instructions. */
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#include<nmmintrin.h>
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#defineCOMP_CRC32C(crc,data,len) \
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((crc) =pg_comp_crc32c_sse42((crc), (data), (len)))
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((crc) =pg_comp_crc32c_dispatch((crc), (data), (len)))
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#defineFIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF)
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externpg_crc32cpg_comp_crc32c_sse42(pg_crc32ccrc,constvoid*data,size_tlen);
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pg_attribute_no_sanitize_alignment()
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staticinline
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pg_crc32c
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pg_comp_crc32c_dispatch(pg_crc32ccrc,constvoid*data,size_tlen)
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{
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if (__builtin_constant_p(len)&&len<32)
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{
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constunsignedchar*p=data;
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/*
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* For small constant inputs, inline the computation to avoid a
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* function call and allow the compiler to unroll loops.
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*/
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#ifSIZEOF_VOID_P >=8
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for (;len >=8;p+=8,len-=8)
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crc=_mm_crc32_u64(crc,*(constuint64*)p);
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#endif
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for (;len >=4;p+=4,len-=4)
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crc=_mm_crc32_u32(crc,*(constuint32*)p);
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for (;len>0;--len)
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crc=_mm_crc32_u8(crc,*p++);
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returncrc;
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}
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else
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returnpg_comp_crc32c_sse42(crc,data,len);
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}
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#elif defined(USE_ARMV8_CRC32C)
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/* Use ARMv8 CRC Extension instructions. */
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