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Diffstat (limited to 'arch/x86/lib/csum-partial_64.c')
-rw-r--r--arch/x86/lib/csum-partial_64.c81
1 files changed, 37 insertions, 44 deletions
diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
index 557e42ede68e..c9dae65ac01b 100644
--- a/arch/x86/lib/csum-partial_64.c
+++ b/arch/x86/lib/csum-partial_64.c
@@ -16,6 +16,20 @@ static inline __wsum csum_finalize_sum(u64 temp64)
return (__force __wsum)((temp64 + ror64(temp64, 32)) >> 32);
}
+static inline unsigned long update_csum_40b(unsigned long sum, const unsigned long m[5])
+{
+ asm("addq %1,%0\n\t"
+ "adcq %2,%0\n\t"
+ "adcq %3,%0\n\t"
+ "adcq %4,%0\n\t"
+ "adcq %5,%0\n\t"
+ "adcq $0,%0"
+ :"+r" (sum)
+ :"m" (m[0]), "m" (m[1]), "m" (m[2]),
+ "m" (m[3]), "m" (m[4]));
+ return sum;
+}
+
/*
* Do a checksum on an arbitrary memory area.
* Returns a 32bit checksum.
@@ -31,52 +45,31 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
{
u64 temp64 = (__force u64)sum;
- /*
- * len == 40 is the hot case due to IPv6 headers, but annotating it likely()
- * has noticeable negative affect on codegen for all other cases with
- * minimal performance benefit here.
- */
- if (len == 40) {
- asm("addq 0*8(%[src]),%[res]\n\t"
- "adcq 1*8(%[src]),%[res]\n\t"
- "adcq 2*8(%[src]),%[res]\n\t"
- "adcq 3*8(%[src]),%[res]\n\t"
- "adcq 4*8(%[src]),%[res]\n\t"
- "adcq $0,%[res]"
- : [res] "+r"(temp64)
- : [src] "r"(buff), "m"(*(const char(*)[40])buff));
- return csum_finalize_sum(temp64);
+ /* Do two 40-byte chunks in parallel to get better ILP */
+ if (likely(len >= 80)) {
+ u64 temp64_2 = 0;
+ do {
+ temp64 = update_csum_40b(temp64, buff);
+ temp64_2 = update_csum_40b(temp64_2, buff + 40);
+ buff += 80;
+ len -= 80;
+ } while (len >= 80);
+
+ asm("addq %1,%0\n\t"
+ "adcq $0,%0"
+ :"+r" (temp64): "r" (temp64_2));
}
- if (unlikely(len >= 64)) {
- /*
- * Extra accumulators for better ILP in the loop.
- */
- u64 tmp_accum, tmp_carries;
- asm("xorl %k[tmp_accum],%k[tmp_accum]\n\t"
- "xorl %k[tmp_carries],%k[tmp_carries]\n\t"
- "subl $64, %[len]\n\t"
- "1:\n\t"
- "addq 0*8(%[src]),%[res]\n\t"
- "adcq 1*8(%[src]),%[res]\n\t"
- "adcq 2*8(%[src]),%[res]\n\t"
- "adcq 3*8(%[src]),%[res]\n\t"
- "adcl $0,%k[tmp_carries]\n\t"
- "addq 4*8(%[src]),%[tmp_accum]\n\t"
- "adcq 5*8(%[src]),%[tmp_accum]\n\t"
- "adcq 6*8(%[src]),%[tmp_accum]\n\t"
- "adcq 7*8(%[src]),%[tmp_accum]\n\t"
- "adcl $0,%k[tmp_carries]\n\t"
- "addq $64, %[src]\n\t"
- "subl $64, %[len]\n\t"
- "jge 1b\n\t"
- "addq %[tmp_accum],%[res]\n\t"
- "adcq %[tmp_carries],%[res]\n\t"
- "adcq $0,%[res]"
- : [tmp_accum] "=&r"(tmp_accum),
- [tmp_carries] "=&r"(tmp_carries), [res] "+r"(temp64),
- [len] "+r"(len), [src] "+r"(buff)
- : "m"(*(const char *)buff));
+ /*
+ * len == 40 is the hot case due to IPv6 headers, so return
+ * early for that exact case without checking the tail bytes.
+ */
+ if (len >= 40) {
+ temp64 = update_csum_40b(temp64, buff);
+ len -= 40;
+ if (!len)
+ return csum_finalize_sum(temp64);
+ buff += 40;
}
if (len & 32) {