On Jun 5, 2012, at 6:46 AM, Paolo Bonzini wrote:
>> Do we always have CTZ if we have FFS? Can't there be a target that
>> implements FFS as opcode but not CTZ, so you'd slow down things?
>> Thus, should the transform be conditonal on target support for CTZ
>> or no target support for FFS?
>
> H
Il 04/06/2012 11:31, Richard Guenther ha scritto:
> +val = compare_range_with_value (NE_EXPR, vr, integer_zero_node,
> &sop);
> +if (!val || !integer_onep (val))
> + return false;
>
> please add a value_range_nonzero_p helper alongside value_range_nonnegative_p.
>
> +
On Sat, Jun 2, 2012 at 1:36 PM, Paolo Bonzini wrote:
> The ffs function can be converted to ctz if the operand is known not
> to be zero, as is the case for example in
>
> while (x != 0) {
> bit = ffs(x) - 1;
> ...
> x &= ~(1 << bit);
> }
>
> CSE can already do this on x86,
The ffs function can be converted to ctz if the operand is known not
to be zero, as is the case for example in
while (x != 0) {
bit = ffs(x) - 1;
...
x &= ~(1 << bit);
}
CSE can already do this on x86, but the attached patch implements this
folding in VRP in a target-
