https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83262
--- Comment #13 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
(In reply to anlauf from comment #11)
> (In reply to Thomas Koenig from comment #9)
> > Created attachment 64471 [details]
> > Updated test case
> >
> > Here's an update on the test case.
>
> You may want to apply:
>
> --- asdf.f90.orig 2026-05-16 16:07:33.523572145 +0200
> +++ asdf.f90 2026-05-16 16:11:51.443302464 +0200
> @@ -204,7 +204,7 @@
>
> do i = 1,N
>
> - key = mod(n,10) + 1
> + key = mod(i,10) + 1
>
> if ( key .eq. 1 ) then
> ss = ss + dble(12)*x1*dble((-1)**key)
> @@ -278,7 +278,7 @@
>
> do i = 1,N
>
> - key = mod(n,10) + 1
> + key = mod(i,10) + 1
>
> if ( key .eq. 1 ) then
> ss = ss + dble(12)*x1*dble((-1)**key)
Ah, I missed those. Thanks for pointing these out.
Now, timings are:
$ gfortran -O1 asdf.f90 && ./a.out 100000000 200000000 300000000
Number of input arguments: 3
GOTO: n =100000000, ss = 0.4321400E+10, time = 0.106 (s)
SELECT CASE: n =100000000, ss = 0.4321400E+10, time = 0.185 (s)
IF-Goto: n =100000000, ss = 0.4321400E+10, time = 0.091 (s)
IF-noGoto: n =100000000, ss = 0.4321400E+10, time = 0.185 (s)
IF-ELSE: n =100000000, ss = 0.4321400E+10, time = 0.185 (s)
GOTO: n =200000000, ss = 0.8642800E+10, time = 0.210 (s)
SELECT CASE: n =200000000, ss = 0.8642800E+10, time = 0.374 (s)
IF-Goto: n =200000000, ss = 0.8642800E+10, time = 0.182 (s)
IF-noGoto: n =200000000, ss = 0.8642800E+10, time = 0.369 (s)
IF-ELSE: n =200000000, ss = 0.8642800E+10, time = 0.369 (s)
GOTO: n =300000000, ss = 0.1296420E+11, time = 0.316 (s)
SELECT CASE: n =300000000, ss = 0.1296420E+11, time = 0.554 (s)
IF-Goto: n =300000000, ss = 0.1296420E+11, time = 0.273 (s)
IF-noGoto: n =300000000, ss = 0.1296420E+11, time = 0.554 (s)
IF-ELSE: n =300000000, ss = 0.1296420E+11, time = 0.554 (s)
GOTO costs totally 0.631 (s)
SELECT CASE costs totally 1.112 (s)
IF-Goto costs totally 0.546 (s)
IF-noGoto costs totally 1.108 (s)
IF-ELSE costs totally 1.108 (s)
$ gfortran -O2 asdf.f90 && ./a.out 100000000 200000000 300000000
Number of input arguments: 3
GOTO: n =100000000, ss = 0.4321400E+10, time = 0.133 (s)
SELECT CASE: n =100000000, ss = 0.4321400E+10, time = 0.126 (s)
IF-Goto: n =100000000, ss = 0.4321400E+10, time = 0.145 (s)
IF-noGoto: n =100000000, ss = 0.4321400E+10, time = 0.143 (s)
IF-ELSE: n =100000000, ss = 0.4321400E+10, time = 0.142 (s)
GOTO: n =200000000, ss = 0.8642800E+10, time = 0.264 (s)
SELECT CASE: n =200000000, ss = 0.8642800E+10, time = 0.253 (s)
IF-Goto: n =200000000, ss = 0.8642800E+10, time = 0.291 (s)
IF-noGoto: n =200000000, ss = 0.8642800E+10, time = 0.286 (s)
IF-ELSE: n =200000000, ss = 0.8642800E+10, time = 0.287 (s)
GOTO: n =300000000, ss = 0.1296420E+11, time = 0.396 (s)
SELECT CASE: n =300000000, ss = 0.1296420E+11, time = 0.380 (s)
IF-Goto: n =300000000, ss = 0.1296420E+11, time = 0.436 (s)
IF-noGoto: n =300000000, ss = 0.1296420E+11, time = 0.427 (s)
IF-ELSE: n =300000000, ss = 0.1296420E+11, time = 0.429 (s)
GOTO costs totally 0.793 (s)
SELECT CASE costs totally 0.760 (s)
IF-Goto costs totally 0.872 (s)
IF-noGoto costs totally 0.856 (s)
IF-ELSE costs totally 0.857 (s)
Total time: 4.138 (s)
so the IF-Goto version is significantly faster than anything else.
That is interesting.:
