Re: [PATCH] fortran: Fix up initializers of param(0) PARAMETERs [PR103691]

[Richard Biener <richard.guenther@gmail.com>]

> Am 26.03.2022 um 12:28 schrieb Thomas Koenig <tkoenig@netcologne.de>:
> 
> On 25.03.22 12:34, Jakub Jelinek via Fortran wrote:
>> What is the behavior with a RANGE_EXPR when one has { [0..10] = ++i;
>> }, is that applying the side-effects 11 times or once ?
> 
> For side effects during the evaluation of expression, Fortran has a
> clear "if you depend on it, it's your fault" rule.  In F 2018, it says
> 
> 10.1.7  Evaluation of operands
> 
> 1 It is not necessary for a processor to evaluate all of the operands of
> an expression, or to evaluate entirely each operand, if the value of the
> expression can be determined otherwise.
> 
> Also, the semantics of
> 
> a(a:b) = expr
> 
> say that the expression on the LHS is evaluated only once before
> assignment.  So, anything that looks like that should be translated
> to
> 
> tmp = ++i;
> [0..10] = tmp;

Note I was not trying to question middle-end semantic here but gfortran se_expr (?) one. Is there a Fortan input where Jakob’s patch would cause a side-effect to be dropped and is that valid?

Richard.

> 
>