From c4eedd9b5362e0bd24af8ac13135ab8caecdca82 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@linux.intel.com>
Date: Tue, 25 Feb 2014 02:07:40 -0800
Subject: [PATCH] hash: reverse the operand order to crc32
Checkin
a132a9cf2bcd440a974b9d3f5c44ba30b2c895a1 hash: use intrinsic
changed the rte_hash_crc.h from using the crc32 instruction via inline
assembly to using an intrinsic. The intrinsic should allow for better
compiler performance, but the change did not account for the fact that
the inline assembly being in AT&T syntax used the opposite operand
order of the intrinsic.
This turns out to not matter for correctness, because the CRC32
operation is commutative. However, it could potentially matter for
performance, because the loop is more efficient with the moving
pointer in the source operand and the accumulation in the destination
operand.
This was discovered by Jan Beulich when looking at the equivalent code
in the Linux kernel.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Reported-by: Jan Beulich <jbeulich@suse.com>
Reported-by: Pashupati Kumar <kumarp@brocade.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>
---
lib/librte_hash/rte_hash_crc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/librte_hash/rte_hash_crc.h b/lib/librte_hash/rte_hash_crc.h
index f6187a0e9a..a849678a43 100644
--- a/lib/librte_hash/rte_hash_crc.h
+++ b/lib/librte_hash/rte_hash_crc.h
@@ -60,7 +60,7 @@ extern "C" {
static inline uint32_t
rte_hash_crc_4byte(uint32_t data, uint32_t init_val)
{
- return _mm_crc32_u32(data, init_val);
+ return _mm_crc32_u32(init_val, data);
}
/**
--
2.39.5