Richard Henderson <r...@twiddle.net> writes:
> On 10/24/2016 09:08 PM, Nikunj A Dadhania wrote:
>> Richard Henderson <r...@twiddle.net> writes:
>>
>>> On 10/24/2016 02:14 AM, Nikunj A Dadhania wrote:
>>>> +#define EXTRACT_BITS(size) \
>>>> +static inline uint##size##_t extract_bits_u##size(uint##size##_t reg, \
>>>> + uint##size##_t start, \
>>>> + uint##size##_t end) \
>>>> +{ \
>>>> + uint##size##_t nr_mask_bits = end - start + 1; \
>>>> + uint##size##_t val = 1; \
>>>> + uint##size##_t mask = (val << nr_mask_bits) - 1; \
>>>> + uint##size##_t shifted_reg = reg >> ((size - 1) - end); \
>>>> + return shifted_reg & mask; \
>>>> +}
>>>> +
>>>> +EXTRACT_BITS(64);
>>>> +EXTRACT_BITS(32);
>>>
>>> We already have extract32 and extract64, which you're (nearly) duplicating.
>>
>> The bit position number notation is different, because of this using the
>> above routine, MSB=0 and LSB=63.
>>
>> While the below assumes: MSB=63 and LSB=0
>>
>> static inline uint64_t extract64(uint64_t value, int start, int length)
>> {
>> assert(start >= 0 && length > 0 && length <= 64 - start);
>> return (value >> start) & (~0ULL >> (64 - length));
>> }
>>
>> Let me know if I am missing something here.
>
> Since the arguments to extract_bits_uN are completely under your control, via
> the arguments to VRLMI, this is a non-argument. Just change them to
> little-endian position + length.
Sure, was already trying that, I have the changed version now:
#define VRLMI(name, size, element, \
begin_last, \
end_last, \
shift_last, num_bits, insert) \
void helper_##name(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b) \
{ \
int i; \
for (i = 0; i < ARRAY_SIZE(r->element); i++) { \
uint##size##_t src1 = a->element[i]; \
uint##size##_t src2 = b->element[i]; \
uint##size##_t src3 = r->element[i]; \
uint##size##_t begin, end, shift, mask, rot_val; \
\
begin = extract##size(src2, size - begin_last - 1, num_bits); \
end = extract##size(src2, size - end_last - 1, num_bits); \
shift = extract##size(src2, size - shift_last - 1, num_bits); \
rot_val = rol##size(src1, shift); \
mask = mask_u##size(begin, end); \
if (insert) { \
r->element[i] = (rot_val & mask) | (src3 & ~mask); \
} else { \
r->element[i] = (rot_val & mask); \
} \
} \
}
VRLMI(vrldmi, 64, u64,
47, /* begin_last */
55, /* end_last */
63, /* shift_last */
6, /* num_bits */
1); /* mask and insert */
>
> (And, after you do that conversion for vrldmi and vilwmi, you'll see why
> big-endian bit numbering is the spawn of the devil. ;-)
That bit numbering gives nightmares ;-)
Regards
Nikunj
