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However, lib/zstd/Makefile compiles at -O2, and BIT_getMiddleBits() only enables the branchless shift-and-mask path on x86_64, falling back to a BIT_mask[] lookup table load on arm64. Add ccflags-y += -O3 to lib/zstd/Makefile and enable the shift-and-mask path in BIT_getMiddleBits() on __aarch64__. On arm64, this reduces zstd CPU cycles by ~7% and improves decompression throughput by 12-23%. Signed-off-by: Jenhao Chen --- lib/zstd/Makefile | 2 ++ lib/zstd/common/bitstream.h | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/lib/zstd/Makefile b/lib/zstd/Makefile index be218b5e0ed59..900922ab5b94a 100644 --- a/lib/zstd/Makefile +++ b/lib/zstd/Makefile @@ -12,6 +12,8 @@ obj-$(CONFIG_ZSTD_COMPRESS) += zstd_compress.o obj-$(CONFIG_ZSTD_DECOMPRESS) += zstd_decompress.o obj-$(CONFIG_ZSTD_COMMON) += zstd_common.o +ccflags-y += -O3 + zstd_compress-y := \ zstd_compress_module.o \ compress/fse_compress.o \ diff --git a/lib/zstd/common/bitstream.h b/lib/zstd/common/bitstream.h index 86439da0eea76..01e69ab7053b4 100644 --- a/lib/zstd/common/bitstream.h +++ b/lib/zstd/common/bitstream.h @@ -299,7 +299,7 @@ FORCE_INLINE_TEMPLATE BitContainerType BIT_getMiddleBits(BitContainerType bitCon * such cpus old (pre-Haswell, 2013) and their performance is not of that * importance. */ -#if defined(__x86_64__) || defined(_M_X64) +#if defined(__x86_64__) || defined(_M_X64) || defined(__aarch64__) return (bitContainer >> (start & regMask)) & ((((U64)1) << nbBits) - 1); #else return (bitContainer >> (start & regMask)) & BIT_mask[nbBits]; -- 2.56.0.317.g454f8302e1-goog