Re: Concertlina II: Full Circle

Stephen Fuld wrote:

Thomas Koenig wrote:

John Savard <quadibloc@servername.invalid> schrieb:

On Tue, 18 Jun 2024 16:17:33 -0000 (UTC), Thomas Koenig
<tkoenig@netcologne.de> wrote:

John Savard <quadibloc@servername.invalid> schrieb:

 

Also, this looping instruction is strictly a way to directly

encode >>> the FORTRAN DO loop. It does not attempt any vectorization.

 

Which one, the FORTRAN 66 one or the one since FORTRAN 77?

 

FORTRAN IV (or 66) indeed.

 It was actually not defined in the standard, in practice it
was usually implemented by a test at the bottom of the loop,
and programs depended on that.
 FORTRAN 77 fixed that, so now
  DO 100 I=1,0
 ...
  100   CONTINUE
 is executed zero times.

How does VVM handle that?  It sems you must "waste" some time, not
executing the loop body until the furst LOOP instruction tells you
whether to or not, or perhaps not actually updating the values the
first time through the loop.  Neither seems optimal.  :-(

The compiler emits code at the top of the loop to branch around the VEC-LOOP bookends.