On 29/05/25 9:05 pm, Segher Boessenkool wrote:
>> +#define _AMO_LD_INCREMENT(NAME, TYPE, OPCODE, FC) \
>> +static __inline__ TYPE
>> \
>> +NAME (TYPE *_PTR) \
>> +{ \
>> + TYPE _RET;
>> \
>> + __asm__ volatile (OPCODE " %[ret],%P[addr],%[code]\n"
>> \
>> + : [addr] "+Q" (_PTR[0]), [ret] "=r" (_RET) \
>> + : "Q" (*(TYPE (*)[2]) _PTR), [code] "n" (FC)); \
>> + return _RET;
>> \
>> +}
>
> I don't understand the [2]. Should it be [1]? These instructions
> can use the value at mem+s (as the ISA names things) as input, but not
> mem+2*s.
The entire expression (*(TYPE (*)[2]) _PTR)) means an array of 2 elements.
Since the _AMO_LD_INCREMENT operation reads two memory locations, hence the [2].
Since the first memory location is already specified in the list of output
operands
as "+Q" (_PTR[0]), so the following should be specified in the list of input
operands:
"Q" ((*(TYPE (*)[2]) _PTR)[1])
Regards,
Surya
