On Thu, Nov 21, 2019 at 10:35 AM Tobias Burnus <tob...@codesourcery.com> wrote:
>
> On 11/20/19 10:35 PM, Thomas König wrote:
> >> Is there a risk of performance regressions due to higher register
> >> pressure?
>
> richi points out (on IRC) that ideally LTO IPA opts would promote the
> call-by reference to call-by value – but is not sure that it indeed
> happens. [In any case, Linux distros have started to compile packages
> with LTO.]
>
> One could try and see whether that indeed happens. – Still, I think the
> real solution is to teach the middle end about the Fortran semantics.
OK, so I found it, it's handled via SSA_NAME_POINTS_TO_READONLY_MEMORY
which is initialized during the rewrite into SSA form from the information
given by the "fn spec" attribute:
for (tree arg = DECL_ARGUMENTS (cfun->decl);
arg; arg = DECL_CHAIN (arg), ++i)
{
if (i >= (unsigned) TREE_STRING_LENGTH (fnspec))
break;
if (TREE_STRING_POINTER (fnspec)[i] == 'R'
|| TREE_STRING_POINTER (fnspec)[i] == 'r')
so when the frontend sets "fn spec" from the intent it should already work.
But the examples I saw above didn't use INTENT(IN) for the scalar parameters.
Richard.
> Cheers,
>
> Tobia
>
>
