Hi Peter,
On Wed, Feb 20, 2019 at 09:19:58PM -0600, Peter Bergner wrote:
> PR89313 exposes a bug in the asmcons pass where it replaces input operands
> with matching constraints with their associated output operands, as well as
> all other uses of its pseudo registers. This is normally fine. However, if
> the matched output operand is marked as early clobber, then we cannot replace
> the uses of 'input' that do not have matching constraints, since they by
> definition conflict with the early clobber output operand and could be
> clobbered if assigned to the same register as the output operand.
>
> The patch below fixes the bug by only doing the input pseudo replacement
> if the output operand is not early clobber or the input operand is known
> to be a matching constraint.
>
> This passed bootstrap and regression testing with no regressions on
> both x86_64-linux and powerpc64le-linux. Ok for mainline?
Looks fine to me, but I cannot approve it of course. Some trivial
comments:
> +/* If CONSTRAINT is a matching constraint, then return its number.
> + Otherwise, return -1. */
> +
> +static int
> +matching_constraint_num (const char *constraint)
> +{
> + int match;
> +
> + if (*constraint == '%')
> + constraint++;
> +
> + switch (*constraint)
> + {
> + case '0': case '1': case '2': case '3': case '4':
> + case '5': case '6': case '7': case '8': case '9':
> + {
> + char *end;
> + match = strtoul (constraint, &end, 10);
> + if (end == constraint)
> + match = -1;
This condition is always false, because we have at least one digit.
> + break;
> + }
> +
> + default:
> + match = -1;
> + break;
> + }
> + return match;
> +}
Which means you can write it as just
static int
matching_constraint_num (const char *constraint)
{
if (*constraint == '%')
constraint++;
if (IN_RANGE (*constraint, '0', '9'))
return strtoul (constraint, NULL, 10);
return -1;
}
Segher
