[PATCH v3] MIPS: Check __clang__ to avoid performance influence with GCC in csum_tcpudp_nofold()
From: Tiezhu Yang
Date: Fri Apr 02 2021 - 06:27:27 EST
The asm code in csum_tcpudp_nofold() is performance critical, I am sorry
for the poorly considered implementation about the performance influence
with GCC in the commit 198688edbf77 ("MIPS: Fix inline asm input/output
type mismatch in checksum.h used with Clang").
Using __clang__ instead of CC_IS_CLANG as check condition, because it
still occurs build error under CC_IS_GCC when make M=samples/bpf which
used with Clang compiler.
With this patch, we can build successfully by both GCC and Clang,
at the same time, the logic is much clear to avoid the potential
performance influence with GCC.
Here are some test data, the config file is loongson3_defconfig, the gcc
version is 10.2.1, we can see that the size has no differences between (1)
and (3).
(1) linux-5.12-rc5.nopatch:
without commit 198688edbf77 ("MIPS: Fix inline asm input/output type
mismatch in checksum.h used with Clang").
(2) linux-5.12-rc5:
with commit 198688edbf77 ("MIPS: Fix inline asm input/output type
mismatch in checksum.h used with Clang").
(3) linux-5.12-rc5.newpatch:
with this patch based on linux-5.12-rc5.
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/vmlinux
text data bss total filename
10273312 3489518 17865568 31628398 linux-5.12-rc5.nopatch/vmlinux
loongson@linux:~$ size --format=GNU linux-5.12-rc5/vmlinux
text data bss total filename
10273536 3489550 17865568 31628654 linux-5.12-rc5/vmlinux
loongson@linux:~$ size --format=GNU linux-5.12-rc5.newpatch/vmlinux
text data bss total filename
10273312 3489518 17865568 31628398 linux-5.12-rc5.newpatch/vmlinux
As far as I can tell, the differences between (1) and (2) is due to the
following affected objects:
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/net/ipv4/tcp_ipv4.o
text data bss total filename
20684 2268 576 23528 linux-5.12-rc5.nopatch/net/ipv4/tcp_ipv4.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5/net/ipv4/tcp_ipv4.o
text data bss total filename
20700 2268 576 23544 linux-5.12-rc5/net/ipv4/tcp_ipv4.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/net/ipv4/tcp_offload.o
text data bss total filename
3584 167 0 3751 linux-5.12-rc5.nopatch/net/ipv4/tcp_offload.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5/net/ipv4/tcp_offload.o
text data bss total filename
3600 167 0 3767 linux-5.12-rc5/net/ipv4/tcp_offload.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/net/ipv4/udp.o
text data bss total filename
30068 3018 32 33118 linux-5.12-rc5.nopatch/net/ipv4/udp.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5/net/ipv4/udp.o
text data bss total filename
30100 3018 32 33150 linux-5.12-rc5/net/ipv4/udp.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/net/ipv4/udp_offload.o
text data bss total filename
6624 311 0 6935 linux-5.12-rc5.nopatch/net/ipv4/udp_offload.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5/net/ipv4/udp_offload.o
text data bss total filename
6640 311 0 6951 linux-5.12-rc5/net/ipv4/udp_offload.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/net/netfilter/nf_nat.o
text data bss total filename
20804 2102 4112 27018 linux-5.12-rc5.nopatch/net/netfilter/nf_nat.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5/net/netfilter/nf_nat.o
text data bss total filename
20820 2102 4112 27034 linux-5.12-rc5/net/netfilter/nf_nat.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/net/netfilter/nf_nat_proto.o
text data bss total filename
7392 770 0 8162 linux-5.12-rc5.nopatch/net/netfilter/nf_nat_proto.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5/net/netfilter/nf_nat_proto.o
text data bss total filename
7408 770 0 8178 linux-5.12-rc5/net/netfilter/nf_nat_proto.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5.nopatch/net/ipv4/netfilter/nf_reject_ipv4.o
text data bss total filename
3776 429 0 4205 linux-5.12-rc5.nopatch/net/ipv4/netfilter/nf_reject_ipv4.o
loongson@linux:~$ size --format=GNU linux-5.12-rc5/net/ipv4/netfilter/nf_reject_ipv4.o
text data bss total filename
3792 429 0 4221 linux-5.12-rc5/net/ipv4/netfilter/nf_reject_ipv4.o
Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
arch/mips/include/asm/checksum.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
index 1e6c135..e1f80407 100644
--- a/arch/mips/include/asm/checksum.h
+++ b/arch/mips/include/asm/checksum.h
@@ -130,7 +130,11 @@ static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
__u32 len, __u8 proto,
__wsum sum)
{
+#ifdef __clang__
unsigned long tmp = (__force unsigned long)sum;
+#else
+ __wsum tmp = sum;
+#endif
__asm__(
" .set push # csum_tcpudp_nofold\n"
--
2.1.0