On Sat, Jun 22, 2013 at 2:59 AM, Dehao Chen <de...@google.com> wrote:
> This patch prevents integer-underflow of badness computation in ipa-inline.
>
> Bootstrapped and passed regression tests.
>
> OK for trunk?
>
> Thanks,
> Dehao
>
> gcc/ChangeLog:
> 2013-06-21 Dehao Chen <de...@google.com>
>
> * ipa-inline.c (edge_badness): Fix integer underflow.
>
> Index: gcc/ipa-inline.c
> ===================================================================
> --- gcc/ipa-inline.c (revision 200326)
> +++ gcc/ipa-inline.c (working copy)
> @@ -888,11 +888,9 @@ edge_badness (struct cgraph_edge *edge, bool dump)
> else if (max_count)
> {
> int relbenefit = relative_time_benefit (callee_info, edge, edge_time);
> - badness =
> - ((int)
> - ((double) edge->count * INT_MIN / 2 / max_count /
> RELATIVE_TIME_BENEFIT_RANGE) *
> - relbenefit) / growth;
> -
> + badness = ((int)((double) edge->count / max_count
> + * relbenefit / RELATIVE_TIME_BENEFIT_RANGE * INT_MIN / 2)) / growth;
> +
FP operations on the host are frowned upon if code generation depends
on their outcome. They all should use sreal_* as predict already does.
Other than that I wonder why the final division is int (so we get truncation
and not rounding)? That increases the effect of doing the multiply by
relbenefit in double.
Richard.
> /* Be sure that insanity of the profile won't lead to increasing counts
> in the scalling and thus to overflow in the computation above. */
> gcc_assert (max_count >= edge->count);
