Question about dump_printf/dump_printf_loc

Question about dump_printf/dump_printf_loc

[Steve Ellcey]

I have a simple question about dump_printf and dump_printf_loc.  I notice
that most (all?) of the uses of these function are of the form:

	if (dump_enabled_p ())
		dump_printf_loc (MSG_*, ......);

Since dump_enabled_p() is just checking to see if dump_file or alt_dump_file
is set and since dump_printf_loc has checks for these as well, is there
any reason why we shouldn't or couldn't just use:

	dump_printf_loc (MSG_*, ......);

with out the call to dump_enabled_p and have the dump function do nothing
when there is no dump file set?  I suppose the first version would have
some performance advantage since dump_enabled_p is an inlined function,
but is that enough of a reason to do it?  The second version seems like
it would look cleaner in the code where we are making these calls.

Steve Ellcey
sellcey@cavium.com

Re: Question about dump_printf/dump_printf_loc

[Richard Biener via gcc]

On Sat, May 6, 2017 at 12:37 AM, Steve Ellcey <sellcey@cavium.com> wrote:
> I have a simple question about dump_printf and dump_printf_loc.  I notice
> that most (all?) of the uses of these function are of the form:
>
>         if (dump_enabled_p ())
>                 dump_printf_loc (MSG_*, ......);
>
> Since dump_enabled_p() is just checking to see if dump_file or alt_dump_file
> is set and since dump_printf_loc has checks for these as well, is there
> any reason why we shouldn't or couldn't just use:
>
>         dump_printf_loc (MSG_*, ......);
>
> with out the call to dump_enabled_p and have the dump function do nothing
> when there is no dump file set?  I suppose the first version would have
> some performance advantage since dump_enabled_p is an inlined function,
> but is that enough of a reason to do it?  The second version seems like
> it would look cleaner in the code where we are making these calls.

The purpose of dump_enabled_p () is to save compile-time for the common case,
esp. when guarding multiple dump_* calls.  But also for the single-called case.
You could try improve things by having inline wrappers for all dump_* cases that
inline a dump_enabled_p () call but that would be somewhat gross.

Richard.

> Steve Ellcey
> sellcey@cavium.com

Re: Question about dump_printf/dump_printf_loc

[Jeff Law]

On 05/05/2017 04:37 PM, Steve Ellcey wrote:
> I have a simple question about dump_printf and dump_printf_loc.  I notice
> that most (all?) of the uses of these function are of the form:
> 
> 	if (dump_enabled_p ())
> 		dump_printf_loc (MSG_*, ......);
> 
> Since dump_enabled_p() is just checking to see if dump_file or alt_dump_file
> is set and since dump_printf_loc has checks for these as well, is there
> any reason why we shouldn't or couldn't just use:
> 
> 	dump_printf_loc (MSG_*, ......);
> 
> with out the call to dump_enabled_p and have the dump function do nothing
> when there is no dump file set?  I suppose the first version would have
> some performance advantage since dump_enabled_p is an inlined function,
> but is that enough of a reason to do it?  The second version seems like
> it would look cleaner in the code where we are making these calls.
> 
I doubt the performance difference is measurable.  More likely than not 
it's just habit.

I tend to perfer the second as it makes the code easier (IMHO) to read.

jeff