| Message ID | 20240221-parisc_use_generic_checksum-v1-4-ad34d895fd1b@rivosinc.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | parisc: checksum: Use generic implementations and optimize checksum | expand |
On Wed, Feb 21, 2024 at 06:37:14PM -0800, Charlie Jenkins wrote: > Replace the shifting and masking of x with a rotation. This generates > better assembly. > > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com> Tested-by: Guenter Roeck <linux@roeck-us.net> > --- > arch/parisc/lib/checksum.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/arch/parisc/lib/checksum.c b/arch/parisc/lib/checksum.c > index eaa660491e24..1ae8cc730d13 100644 > --- a/arch/parisc/lib/checksum.c > +++ b/arch/parisc/lib/checksum.c > @@ -27,11 +27,8 @@ > > static inline unsigned short from32to16(unsigned int x) > { > - /* 32 bits --> 16 bits + carry */ > - x = (x & 0xffff) + (x >> 16); > - /* 16 bits + carry --> 16 bits including carry */ > - x = (x & 0xffff) + (x >> 16); > - return (unsigned short)x; > + x += ror32(x, 16); > + return (unsigned short)(x >> 16); > } > > unsigned int do_csum(const unsigned char *buff, int len) > > -- > 2.34.1 >
diff --git a/arch/parisc/lib/checksum.c b/arch/parisc/lib/checksum.c index eaa660491e24..1ae8cc730d13 100644 --- a/arch/parisc/lib/checksum.c +++ b/arch/parisc/lib/checksum.c @@ -27,11 +27,8 @@ static inline unsigned short from32to16(unsigned int x) { - /* 32 bits --> 16 bits + carry */ - x = (x & 0xffff) + (x >> 16); - /* 16 bits + carry --> 16 bits including carry */ - x = (x & 0xffff) + (x >> 16); - return (unsigned short)x; + x += ror32(x, 16); + return (unsigned short)(x >> 16); } unsigned int do_csum(const unsigned char *buff, int len)
Replace the shifting and masking of x with a rotation. This generates better assembly. Signed-off-by: Charlie Jenkins <charlie@rivosinc.com> --- arch/parisc/lib/checksum.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)