On Mon, Jul 15, 2013 at 7:32 PM, Kenneth Graunke <kenn...@whitecape.org> wrote:
> The GL_ARB_shading_language_420pack extension/GLSL 4.20 allow qualifiers
> to be specified in (basically) any order. In order to support this, we
> can't hardcode the ordering restrictions in the grammar.
>
> This patch alters the grammar to accept invariant, storage, layout, and
> interpolation qualifiers in any order, but adds C code to enforce the
> ordering requirements. In the 420pack case, we should be able to simply
> skip the error checks.
>
> As a bonus, this also lets us generate decent error messages, rather
> than Bison's awful "unexpected TOKEN" errors.
>
> Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
> ---
> src/glsl/glsl_parser.yy | 110
> ++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 92 insertions(+), 18 deletions(-)
>
> diff --git a/src/glsl/glsl_parser.yy b/src/glsl/glsl_parser.yy
> index b8f3df9..72bf560 100644
> --- a/src/glsl/glsl_parser.yy
> +++ b/src/glsl/glsl_parser.yy
> @@ -1314,34 +1314,108 @@ parameter_type_qualifier:
> ;
>
> type_qualifier:
> - storage_qualifier
> - | layout_qualifier
> - | layout_qualifier storage_qualifier
> + /* Single qualifiers */
> + INVARIANT
> {
> - $$ = $1;
> - $$.flags.i |= $2.flags.i;
> + memset(& $$, 0, sizeof($$));
> + $$.flags.q.invariant = 1;
> }
> + | storage_qualifier
> | interpolation_qualifier
> - | interpolation_qualifier storage_qualifier
> - {
> - $$ = $1;
> - $$.flags.i |= $2.flags.i;
> - }
> - | INVARIANT storage_qualifier
> + | layout_qualifier
> +
> + /* Multiple qualifiers:
> + * In GLSL 4.20, these can be specified in any order. In earlier
> versions,
> + * they appear in this order (see GLSL 1.50 section 4.7 & comments below):
> + *
> + * invariant interpolation storage precision ...or...
> + * layout storage precision
> + *
> + * Each qualifier's rule ensures that the accumulated qualifiers on the
> right
> + * side don't contain any that must appear on the left hand side.
> + * For example, when processing a storage qualifier, we check that there
> are
> + * no interpolation, layout, or invariant qualifiers to the right.
> + */
> + | INVARIANT type_qualifier
> {
> + if ($2.flags.q.invariant)
> + _mesa_glsl_error(&@1, state, "Duplicate \"invariant\"
> qualifier.\n");
> +
> + if ($2.has_layout()) {
> + _mesa_glsl_error(&@1, state,
> + "\"invariant\" cannot be used with
> layout(...).\n");
> + }
> +
> $$ = $2;
> $$.flags.q.invariant = 1;
> }
> - | INVARIANT interpolation_qualifier storage_qualifier
> + | interpolation_qualifier type_qualifier
> + {
> + /* Section 4.3 of the GLSL 1.40 specification states:
> + * "...qualified with one of these interpolation qualifiers"
> + *
> + * GLSL 1.30 claims to allow "one or more", but insists that:
> + * "These interpolation qualifiers may only precede the qualifiers in,
> + * centroid in, out, or centroid out in a declaration."
> + *
> + * ...which means that e.g. smooth can't precede smooth, so there can
> be
> + * only one after all, and the 1.40 text is a clarification, not a
> change.
> + */
> + if ($2.has_interpolation())
> + _mesa_glsl_error(&@1, state, "Duplicate interpolation
> qualifier.\n");
> +
> + if ($2.has_layout()) {
> + _mesa_glsl_error(&@1, state, "Interpolation qualifiers cannot be
> used "
> + "with layout(...).\n");
> + }
> +
> + if ($2.flags.q.invariant) {
> + _mesa_glsl_error(&@1, state, "Interpolation qualifiers must come "
> + "after \"invariant\".\n");
> + }
> +
> + $$ = $1;
> + $$.flags.i |= $2.flags.i;
> + }
> + | layout_qualifier type_qualifier
> {
> - $$ = $2;
> - $$.flags.i |= $3.flags.i;
> - $$.flags.q.invariant = 1;
> + /* The GLSL 1.50 grammar indicates that a layout(...) declaration can
> be
> + * used standalone or immediately before a storage qualifier. It
> cannot
> + * be used with interpolation qualifiers or invariant. There does not
> + * appear to be any text indicating that it must come before the
> storage
> + * qualifier, but always seems to in examples.
> + */
> + if ($2.has_layout())
Should be
if (!state->ARB_shading_language_420pack_enable && $2.has_layout())
Since duplicate layout qualifiers are explicitly allowed.
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