One could also simply remove the error in varasm.c. This
would preserve the optimization. As a side effect, this
would allow register without __asm__ at file scope, but
there do not seem to be any disadvantages. (register
at file scope is already diagnosed by the C FE when
using --pedantic).
Best,
Martin
Am Donnerstag, den 27.02.2020, 10:31 +0100 schrieb Richard Biener:
> On Thu, 27 Feb 2020, Jakub Jelinek wrote:
>
> > Hi!
> >
> > The following testcase is rejected, while it was accepted in 3.4 and earlier
> > (before tree-ssa merge).
> > The problem is that we decide to promote the const variable to TREE_STATIC,
> > but TREE_STATIC DECL_REGISTER VAR_DECLs may only be the global register vars
> > and so assemble_variable/make_decl_rtl diagnoses it.
> >
> > Either we do what the following patch does, where we could consider
> > register as a hint the user doesn't want such optimization, because if
> > something is forced static, it is not "register" anymore and register static
> > is not valid in C either, or we could clear DECL_REGISTER instead, but would
> > still need to punt at least on DECL_HARD_REGISTER cases.
> >
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> OK.
>
> Thanks,
> Richard.
>
> > 2020-02-27 Jakub Jelinek <ja...@redhat.com>
> >
> > PR c/93949
> > * gimplify.c (gimplify_init_constructor): Don't promote readonly
> > DECL_REGISTER variables to TREE_STATIC.
> >
> > * gcc.c-torture/compile/pr93949.c: New test.
> >
> > --- gcc/gimplify.c.jj 2020-02-25 13:54:02.087091120 +0100
> > +++ gcc/gimplify.c 2020-02-26 19:30:57.466490166 +0100
> > @@ -4923,6 +4923,7 @@ gimplify_init_constructor (tree *expr_p,
> > && num_nonzero_elements > 1
> > && TREE_READONLY (object)
> > && VAR_P (object)
> > + && !DECL_REGISTER (object)
> > && (flag_merge_constants >= 2 || !TREE_ADDRESSABLE (object))
> > /* For ctors that have many repeated nonzero elements
> > represented through RANGE_EXPRs, prefer initializing
> > --- gcc/testsuite/gcc.c-torture/compile/pr93949.c.jj 2020-02-26
> > 19:42:15.754530691 +0100
> > +++ gcc/testsuite/gcc.c-torture/compile/pr93949.c 2020-02-26
> > 19:42:08.153642329 +0100
> > @@ -0,0 +1,7 @@
> > +/* PR c/93949 */
> > +
> > +void
> > +foo (void)
> > +{
> > + register const double d[3] = { 0., 1., 2. };
> > +}
> >
> > Jakub
> >
> >
>
>
