Re: [PATCH] Fold VIEW_CONVERT_EXPR <type, STRING_CST> generated by Fortran FE a lot (PR target/35366)

[Tobias Schlüter <Tobias dot Schlueter at physik dot uni-muenchen dot de>]

Jakub Jelinek wrote:
> Unfortrunately, it causes 2 Fortran testsuite failures, hollerith.f90
> and transfer_simplify_4.f90, both at all optimization levels.
> I believe the tests are just invalid though.  The first one does:
> logical l
> l = 4Ho wo
> and expects all the 32 bits preserved, but that is certainly against
> the semantics of BOOLEAN_TYPE and from quick skimming of the Fortran
> standard also LOGICAL type.  BOOLEAN_TYPE has just two values, false
> and true (similarly for LOGICAL .false. and .true.) and so the folder
> IMHO correctly folds this into
> l = .true.
> (4Ho wo is non-zero).  The transfer_simplify_4.f90 testcase transfers an
> integer into logical and back and expects again all the 32-bits to be
> preserved.
>
> Fortran folks, can you please look at these 2 testcases and say whether
> they are valid Fortran or just undefined behavior?

They are not standard Fortran.  Using Hollerith constants this way was 
the way of encoding strings before there was a Character type in 
Fortran, so the current behavior is intentional.  Whether there actually 
is code that uses logicals to encode strings, I can't tell.  I CCed Feng 
Wang who added the original Hollerith support, and Steve who last 
modified the testcase.

Cheers,
- Tobi