Messages in this thread | | | Subject | Re: [patch V4 09/31] bitops: Add x86-specific parity functions | From | "H. Peter Anvin" <> | Date | Mon, 16 May 2016 12:19:15 -0700 |
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On May 11, 2016 2:31:39 AM PDT, Peter Zijlstra <peterz@infradead.org> wrote: >On Wed, May 11, 2016 at 05:16:38PM +0800, zengzhaoxiu@163.com wrote: > >> +static inline unsigned int __arch_parity4(unsigned int w) >> +{ >> + unsigned int res = 0; >> + >> + asm("test $0xf, %1; setpo %b0" >> + : "+q" (res) >> + : "r" (w) >> + : "cc"); >> + >> + return res; >> +} >> + >> +static inline unsigned int __arch_parity8(unsigned int w) >> +{ >> + unsigned int res = 0; >> + >> + asm("test %1, %1; setpo %b0" >> + : "+q" (res) >> + : "r" (w) >> + : "cc"); >> + >> + return res; >> +} >> + >> +static inline unsigned int __arch_parity16(unsigned int w) >> +{ >> + unsigned int res = 0; >> + >> + asm("xor %h1, %b1; setpo %b0" >> + : "+q" (res), "+q" (w) >> + : : "cc"); >> + >> + return res; >> +} > >Please use the GEN_*_RMWcc() stuff to avoid the setpo where possible. > >> + >> +#ifdef CONFIG_64BIT >> +/* popcnt %eax, %eax -- redundant REX prefix for alignment */ >> +#define POPCNT32 ".byte 0xf3,0x40,0x0f,0xb8,0xc0" >> +/* popcnt %rax, %rax */ >> +#define POPCNT64 ".byte 0xf3,0x48,0x0f,0xb8,0xc0" >> +#else >> +/* popcnt %eax, %eax */ >> +#define POPCNT32 ".byte 0xf3,0x0f,0xb8,0xc0" >> +#endif > >Yuck, please don't duplicate stuff like this. > >> + >> +static __always_inline unsigned int __arch_parity32(unsigned int w) >> +{ >> + unsigned int res; >> + unsigned int tmp; >> + >> + asm(ALTERNATIVE( >> + " mov %%eax, %1 \n" >> + " shr $16, %%eax \n" >> + " xor %1, %%eax \n" >> + " xor %%ah, %%al \n" >> + " mov $0, %%eax \n" >> + " setpo %%al \n", >> + POPCNT32 " \n" >> + " and $1, %%eax \n", >> + X86_FEATURE_POPCNT) >> + : "=a" (res), "=&r" (tmp) >> + : "a" (w) >> + : "cc"); >> + >> + return res; >> +} > >How many bytes does that end up being? Should we make it a call?
Also, setxx is used with a "bool" or "u8", not " unsigned int"!!!! -- Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.
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