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([2406:7400:56:e503:ad72:fda5:83e8:be95]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-33255d39d21sm7358074eec.16.2026.09.03.05.35.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Sep 2026 05:35:27 -0700 (PDT) Message-ID: Date: Thu, 3 Sep 2026 18:05:17 +0530 Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] lib/zstd: add fallback aliases for disabled BMI2 variants To: Usama Arif , dsterba@suse.com, linux-kernel@vger.kernel.org, terrelln@fb.com, terrelln@meta.com, linux-crypto@vger.kernel.org, yosry@kernel.org, ebiggers@kernel.org, torvalds@linux-foundation.org Cc: hannes@cmpxchg.org, nphamcs@gmail.com, chengming.zhou@linux.dev, shakeel.butt@linux.dev, kernel-team@meta.com References: <20260901110850.1805747-1-usama.arif@linux.dev> <20260901110850.1805747-2-usama.arif@linux.dev> Content-Language: en-US From: Dhruva G In-Reply-To: <20260901110850.1805747-2-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 01-09-2026 16:37, Usama Arif wrote: > When dynamic BMI2 dispatch is disabled, the BMI2-specific functions are > not compiled and each selector is conditionally compiled to avoid naming > them. > > The selector-level preprocessor guards will be replaced with a predicate > that becomes constant false when dynamic BMI2 dispatch is disabled. > Although the compiler eliminates an `if (0)` branch, it must still parse > and resolve the BMI2 function referenced by it. > > Add aliases from the unavailable BMI2 function names to their default > implementations. These aliases make the names valid without emitting > BMI2-specific code. The selectors remain unchanged in this patch, so the > aliases are not used yet and there is no code-generation change. > > Signed-off-by: Usama Arif > --- Reviewed-by: Dhruva Gole > lib/zstd/common/entropy_common.c | 4 ++++ > lib/zstd/common/fse_decompress.c | 2 ++ > lib/zstd/compress/zstd_compress_sequences.c | 4 ++++ > lib/zstd/decompress/huf_decompress.c | 4 ++++ > lib/zstd/decompress/zstd_decompress_block.c | 12 ++++++++++++ > 5 files changed, 26 insertions(+) > > diff --git a/lib/zstd/common/entropy_common.c b/lib/zstd/common/entropy_common.c > index 6cdd82233fb59..15a7c14ae8040 100644 > --- a/lib/zstd/common/entropy_common.c > +++ b/lib/zstd/common/entropy_common.c > @@ -202,6 +202,8 @@ BMI2_TARGET_ATTRIBUTE static size_t FSE_readNCount_body_bmi2( > { > return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize); > } > +#else > +#define FSE_readNCount_body_bmi2 FSE_readNCount_body_default > #endif > > size_t FSE_readNCount_bmi2( > @@ -323,6 +325,8 @@ static BMI2_TARGET_ATTRIBUTE size_t HUF_readStats_body_bmi2(BYTE* huffWeight, si > { > return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 1); > } > +#else > +#define HUF_readStats_body_bmi2 HUF_readStats_body_default > #endif > > size_t HUF_readStats_wksp(BYTE* huffWeight, size_t hwSize, U32* rankStats, > diff --git a/lib/zstd/common/fse_decompress.c b/lib/zstd/common/fse_decompress.c > index 15081d8dc607c..8d9c43b928833 100644 > --- a/lib/zstd/common/fse_decompress.c > +++ b/lib/zstd/common/fse_decompress.c > @@ -300,6 +300,8 @@ BMI2_TARGET_ATTRIBUTE static size_t FSE_decompress_wksp_body_bmi2(void* dst, siz > { > return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 1); > } > +#else > +#define FSE_decompress_wksp_body_bmi2 FSE_decompress_wksp_body_default > #endif > > size_t FSE_decompress_wksp_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize, int bmi2) > diff --git a/lib/zstd/compress/zstd_compress_sequences.c b/lib/zstd/compress/zstd_compress_sequences.c > index 256980c9d85ad..64abcdf2c5714 100644 > --- a/lib/zstd/compress/zstd_compress_sequences.c > +++ b/lib/zstd/compress/zstd_compress_sequences.c > @@ -415,6 +415,10 @@ ZSTD_encodeSequences_bmi2( > sequences, nbSeq, longOffsets); > } > > +#else > + > +#define ZSTD_encodeSequences_bmi2 ZSTD_encodeSequences_default > + > #endif > > size_t ZSTD_encodeSequences( > diff --git a/lib/zstd/decompress/huf_decompress.c b/lib/zstd/decompress/huf_decompress.c > index ac8b87f48f847..5663ae524cd83 100644 > --- a/lib/zstd/decompress/huf_decompress.c > +++ b/lib/zstd/decompress/huf_decompress.c > @@ -700,6 +700,8 @@ size_t HUF_decompress4X1_usingDTable_internal_bmi2(void* dst, size_t dstSize, vo > size_t cSrcSize, HUF_DTable const* DTable) { > return HUF_decompress4X1_usingDTable_internal_body(dst, dstSize, cSrc, cSrcSize, DTable); > } > +#else > +#define HUF_decompress4X1_usingDTable_internal_bmi2 HUF_decompress4X1_usingDTable_internal_default > #endif > > static > @@ -1503,6 +1505,8 @@ size_t HUF_decompress4X2_usingDTable_internal_bmi2(void* dst, size_t dstSize, vo > size_t cSrcSize, HUF_DTable const* DTable) { > return HUF_decompress4X2_usingDTable_internal_body(dst, dstSize, cSrc, cSrcSize, DTable); > } > +#else > +#define HUF_decompress4X2_usingDTable_internal_bmi2 HUF_decompress4X2_usingDTable_internal_default > #endif > > static > diff --git a/lib/zstd/decompress/zstd_decompress_block.c b/lib/zstd/decompress/zstd_decompress_block.c > index 710eb0ffd5a37..9c4215e435014 100644 > --- a/lib/zstd/decompress/zstd_decompress_block.c > +++ b/lib/zstd/decompress/zstd_decompress_block.c > @@ -622,6 +622,8 @@ BMI2_TARGET_ATTRIBUTE static void ZSTD_buildFSETable_body_bmi2(ZSTD_seqSymbol* d > ZSTD_buildFSETable_body(dt, normalizedCounter, maxSymbolValue, > baseValue, nbAdditionalBits, tableLog, wksp, wkspSize); > } > +#else > +#define ZSTD_buildFSETable_body_bmi2 ZSTD_buildFSETable_body_default > #endif > > void ZSTD_buildFSETable(ZSTD_seqSymbol* dt, > @@ -1934,6 +1936,16 @@ ZSTD_decompressSequencesLong_bmi2(ZSTD_DCtx* dctx, > } > #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */ > > +#else > + > +#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG > +#define ZSTD_decompressSequences_bmi2 ZSTD_decompressSequences_default > +#define ZSTD_decompressSequencesSplitLitBuffer_bmi2 ZSTD_decompressSequencesSplitLitBuffer_default > +#endif > +#ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT > +#define ZSTD_decompressSequencesLong_bmi2 ZSTD_decompressSequencesLong_default > +#endif > + > #endif /* DYNAMIC_BMI2 */ > > #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG