http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57904
--- Comment #13 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
(In reply to Jakub Jelinek from comment #12)
> But you can always create testcases (in C/C++ etc.) that will hit this
> warning, so while the FE change is possible, we need to do something either
> about the optimization passes in between IPA and cunrolli (copyprop change
> Jeff talks about, perhaps only done for that single pass instance and not
> others, or all?, guess depending on how expensive it is) or scheduling there
> another instance of some other cleanup pass, or deferring the warning
> reporting until some cleanup.
>
Could someone please provide a C test case that generates this warning?
maybe something like:
int dovar = from;
if (dovar <= to)
for (;;)
{
...
if (dovar == to)
break;
dovar += step;
}
> For the FE change, I guess most important are benchmark results, doesn't it
> slow down important benchmarks?
I think the change in the simple DO-loops really makes sense,
independent of this warning.
It generates the IL code just a bit more like it is done in C:
for (dovar=from; dovar <= to; dovar+=step) { ... }
=>
dovar = from;
if (dovar <= to)
{
loop:
...
dovar+=step;
if (dovar <= to)
goto loop;
}
Therefore the IL is easier to analyze and
chances are good that the optimizer performs better.
I can't do these benchmarks however. Who could do that for us?
