On Sat, Feb 27, 2016 at 12:30 AM, Alexander Duyck <alexander.du...@gmail.com> wrote: >> +{ >> + asm("lea 40f(, %[slen], 4), %%r11\n\t" >> + "clc\n\t" >> + "jmpq *%%r11\n\t" >> + "adcq 7*8(%[src]),%[res]\n\t" >> + "adcq 6*8(%[src]),%[res]\n\t" >> + "adcq 5*8(%[src]),%[res]\n\t" >> + "adcq 4*8(%[src]),%[res]\n\t" >> + "adcq 3*8(%[src]),%[res]\n\t" >> + "adcq 2*8(%[src]),%[res]\n\t" >> + "adcq 1*8(%[src]),%[res]\n\t" >> + "adcq 0*8(%[src]),%[res]\n\t" >> + "nop\n\t" >> + "40: adcq $0,%[res]" >> + : [res] "=r" (sum) >> + : [src] "r" (buff), >> + [slen] "r" (-((unsigned long)(len >> 3))), "[res]" >> (sum) >> + : "r11"); >> + > > With this patch I cannot mix/match different length checksums without > things failing. In perf the jmpq in the loop above seems to be set to > a fixed value so perhaps it is something in how the compiler is > interpreting the inline assembler.
The perf thing was a red herring. Turns out the code is working correctly there. I actually found the root cause. The problem is in add32_with_carry3. > +static inline unsigned int add32_with_carry3(unsigned int a, unsigned int b, > + unsigned int c) > +{ > + asm("addl %2,%0\n\t" > + "adcl %3,%0\n\t" > + "adcl $0,%0" > + : "=r" (a) > + : "" (a), "rm" (b), "rm" (c)); > + > + return a; > +} > + You need to set the 'a' input variable attribute to "0" instead of "" and then things work for me correctly. - Alex