Mesa (main): glsl: Fix subscripted arrays with no XFB packing

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Module: Mesa
Branch: main
Commit: 538ab8c5710d13499a65c92f0ac49fc8ab2e3880
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=538ab8c5710d13499a65c92f0ac49fc8ab2e3880

Author: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Date:   Thu Aug 27 08:21:40 2020 -0400

glsl: Fix subscripted arrays with no XFB packing

We need to duplicate the subscripted members even if they happen to be
aligned, since the other elements may be passed into the consumer
shader. Fixes on Panfrost:

dEQP-GLES3.functional.transform_feedback.array_element.interleaved.lines.highp_float

Note: the test did pass on main previously due to an elaborate set of
driver hacks. I don't believe the old behaviour was correct regardless.

Only Panfrost is affected by this change and the next, as every other
driver sets PIPE_CAP_PACKED_STREAM_OUTPUT.

Acked-by: Erik Faye-Lund <erik.faye-lund at collabora.com>
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10778>

---

 src/compiler/glsl/link_varyings.cpp | 8 +++-----
 src/compiler/glsl/link_varyings.h   | 4 ++--
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
index dc5cb65612a..43570de47a1 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -2925,17 +2925,15 @@ assign_varying_locations(struct gl_context *ctx,
       /* There are two situations where a new output varying is needed:
        *
        *  - If varying packing is disabled for xfb and the current declaration
-       *    is not aligned within the top level varying (e.g. vec3_arr[1]).
+       *    is subscripting an array, whether the subscript is aligned or not.
+       *    to preserve the rest of the array for the consumer.
        *
        *  - If a builtin variable needs to be copied to a new variable
        *    before its content is modified by another lowering pass (e.g.
        *    \c gl_Position is transformed by \c nir_lower_viewport_transform).
        */
-      const unsigned dmul =
-         matched_candidate->type->without_array()->is_64bit() ? 2 : 1;
       const bool lowered =
-         (disable_xfb_packing &&
-          !tfeedback_decls[i].is_aligned(dmul, matched_candidate->struct_offset_floats)) ||
+         (disable_xfb_packing && tfeedback_decls[i].subscripted()) ||
          (matched_candidate->toplevel_var->data.explicit_location &&
           matched_candidate->toplevel_var->data.location < VARYING_SLOT_VAR0 &&
           (!consumer || consumer->Stage == MESA_SHADER_FRAGMENT) &&
diff --git a/src/compiler/glsl/link_varyings.h b/src/compiler/glsl/link_varyings.h
index 87d7f43998e..1147117f052 100644
--- a/src/compiler/glsl/link_varyings.h
+++ b/src/compiler/glsl/link_varyings.h
@@ -130,9 +130,9 @@ public:
       return !this->next_buffer_separator && !this->skip_components;
    }
 
-   bool is_aligned(unsigned dmul, unsigned offset) const
+   bool subscripted() const
    {
-      return (dmul * (this->array_subscript + offset)) % 4 == 0;
+      return this->is_subscripted;
    }
 
    const char *name() const