On Wed, Jul 30, 2025 at 10:16:06AM +0200, Jakub Jelinek wrote:
> Or maybe better
> _BitInt(PROMOTED_SIZE (x) * __CHAR_BIT__) __x;
> int __y = S (x);
> do_copy (&__x, &(x), sizeof (__x));
> if (__y < PROMOTED_SIZE (x) * __CHAR_BIT__)
> {
> int __neg = __x < 0;
> __x >>= PROMOTED_SIZE (x) * __CHAR_BIT__ - __y;
Obviously __x >>= __y;
We want to shift away all the normal bits and keep just the padding bits
which aren't padding in the promoted type.
> if (__x != (__neg ? (typeof (__x)) -1 : (__typeof (__x)) 0))
> __builtin_abort ();
> }
> and just no __neg and if (__x) in the unsigned case?
> The intent is not to invoke any UB, just have the memcpy hidden
> from the optimizers.
Jakub
