linux-kernel - [PATCH] zstd: Fix decompression of large window archives on 32-bit platforms

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Message-Id: <20200914061931.21886-1-oss@malat.biz>
Date:   Mon, 14 Sep 2020 08:19:31 +0200
From:   Petr Malat <oss@...at.biz>
To:     linux-kernel@...r.kernel.org
Cc:     nickrterrell@...il.com, gustavoars@...nel.org,
        Petr Malat <oss@...at.biz>
Subject: [PATCH] zstd: Fix decompression of large window archives on 32-bit platforms

It seems some optimization has been removed from the code without removing
the if condition which should activate it only on 64-bit platforms and as
a result the code responsible for decompression with window larger than
8MB was disabled on 32-bit platforms.

Signed-off-by: Petr Malat <oss@...at.biz>
---
 lib/zstd/decompress.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/lib/zstd/decompress.c b/lib/zstd/decompress.c
index db6761ea4deb..509a3b8d51b9 100644
--- a/lib/zstd/decompress.c
+++ b/lib/zstd/decompress.c
@@ -1457,12 +1457,8 @@ static size_t ZSTD_decompressBlock_internal(ZSTD_DCtx *dctx, void *dst, size_t d
 		ip += litCSize;
 		srcSize -= litCSize;
 	}
-	if (sizeof(size_t) > 4) /* do not enable prefetching on 32-bits x86, as it's performance detrimental */
-				/* likely because of register pressure */
-				/* if that's the correct cause, then 32-bits ARM should be affected differently */
-				/* it would be good to test this on ARM real hardware, to see if prefetch version improves speed */
-		if (dctx->fParams.windowSize > (1 << 23))
-			return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize);
+	if (dctx->fParams.windowSize > (1 << 23))
+		return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize);
 	return ZSTD_decompressSequences(dctx, dst, dstCapacity, ip, srcSize);
 }
 
-- 
2.20.1