[PATCH] net/crc: reduce usage of static arrays in net_crc_sse.c

[PATCH] net/crc: reduce usage of static arrays in net_crc_sse.c

[Shreesh Adiga]

Replace the clearing of lower 32 bits of XMM register with blend of
zero register.
Replace the clearing of upper 64 bits of XMM register with _mm_move_epi64.
Clang is able to optimize away the AND + memory operand with the
above sequence, however GCC is still emitting the code for AND with
memory operands which is being explicitly eliminated here.

Additionally replace the 48 byte crc_xmm_shift_tab with the contents of
shf_table which is 32 bytes, achieving the same functionality.

Signed-off-by: Shreesh Adiga <16567adigashreesh@gmail.com>
---
 lib/net/net_crc_sse.c | 30 +++++++-----------------------
 1 file changed, 7 insertions(+), 23 deletions(-)

diff --git a/lib/net/net_crc_sse.c b/lib/net/net_crc_sse.c
index 112dc94ac1..eec854e587 100644
--- a/lib/net/net_crc_sse.c
+++ b/lib/net/net_crc_sse.c
@@ -96,20 +96,13 @@ crcr32_reduce_128_to_64(__m128i data128, __m128i precomp)
 static __rte_always_inline uint32_t
 crcr32_reduce_64_to_32(__m128i data64, __m128i precomp)
 {
-	static const alignas(16) uint32_t mask1[4] = {
-		0xffffffff, 0xffffffff, 0x00000000, 0x00000000
-	};
-
-	static const alignas(16) uint32_t mask2[4] = {
-		0x00000000, 0xffffffff, 0xffffffff, 0xffffffff
-	};
 	__m128i tmp0, tmp1, tmp2;
 
-	tmp0 = _mm_and_si128(data64, _mm_load_si128((const __m128i *)mask2));
+	tmp0 = _mm_blend_epi16(_mm_setzero_si128(), data64, 252);
 
 	tmp1 = _mm_clmulepi64_si128(tmp0, precomp, 0x00);
 	tmp1 = _mm_xor_si128(tmp1, tmp0);
-	tmp1 = _mm_and_si128(tmp1, _mm_load_si128((const __m128i *)mask1));
+	tmp1 = _mm_move_epi64(tmp1);
 
 	tmp2 = _mm_clmulepi64_si128(tmp1, precomp, 0x10);
 	tmp2 = _mm_xor_si128(tmp2, tmp1);
@@ -118,13 +111,11 @@ crcr32_reduce_64_to_32(__m128i data64, __m128i precomp)
 	return _mm_extract_epi32(tmp2, 2);
 }
 
-static const alignas(16) uint8_t crc_xmm_shift_tab[48] = {
-	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+static const alignas(16) uint8_t crc_xmm_shift_tab[32] = {
+	0x00, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+	0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
 	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
-	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
+	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
 };
 
 /**
@@ -216,19 +207,12 @@ crc32_eth_calc_pclmulqdq(
 			0x80808080, 0x80808080, 0x80808080, 0x80808080
 		};
 
-		const alignas(16) uint8_t shf_table[32] = {
-			0x00, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
-			0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
-			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-			0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
-		};
-
 		__m128i last16, a, b;
 
 		last16 = _mm_loadu_si128((const __m128i *)&data[data_len - 16]);
 
 		temp = _mm_loadu_si128((const __m128i *)
-			&shf_table[data_len & 15]);
+			&crc_xmm_shift_tab[data_len & 15]);
 		a = _mm_shuffle_epi8(fold, temp);
 
 		temp = _mm_xor_si128(temp,
-- 
2.49.1