Mesa (9.2): glsl: Allow precision qualifiers for sampler types

[Ian Romanick]

Module: Mesa
Branch: 9.2
Commit: 26ae6ec1e87a9b932e57e99a785b229ff72cf551
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=26ae6ec1e87a9b932e57e99a785b229ff72cf551

Author: Anuj Phogat <anuj.phogat at gmail.com>
Date:   Mon Aug 26 18:21:03 2013 -0700

glsl: Allow precision qualifiers for sampler types

GLSL 1.30 doesn't allow precision qualifiers on sampler types,
but in GLSL ES, sampler types are also allowed. This seems like
an oversight (since the intention of including these in GLSL 1.30
is to allow compatibility with ES shaders).

Currently, Mesa allows "default" precision qualifiers to be set for
sampler types in GLSL (commit d5948f2). This patch makes it follow
GLSL ES rules and also allow declaring sampler variables with a
precision qualifier in GLSL 1.30 (and later). e.g.
uniform lowp sampler2D sampler;

This fixes a shader compilation error in Khronos OpenGL conformance
test "depth_texture_mipmap".

V2: Update comments.
Signed-off-by: Ian Romanick <idr at lists.freedesktop.org>

Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
Reviewed-by: Ian Romanick <idr at lists.freedesktop.org>
Cc: <mesa-stable at lists.freedesktop.org>
(cherry picked from commit 9c0b7be964f0cbb707ed11c2526a30eda5254d2e)

---

 src/glsl/ast_to_hir.cpp |   29 +++++++++++++++++++++--------
 1 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 6164f76..0481b1f 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -3006,32 +3006,45 @@ ast_declarator_list::hir(exec_list *instructions,
       }
 
 
-      /* Precision qualifiers only apply to floating point and integer types.
+      /* Precision qualifiers apply to floating point, integer and sampler
+       * types.
        *
-       * From section 4.5.2 of the GLSL 1.30 spec:
+       * Section 4.5.2 (Precision Qualifiers) of the GLSL 1.30 spec says:
        *    "Any floating point or any integer declaration can have the type
        *    preceded by one of these precision qualifiers [...] Literal
        *    constants do not have precision qualifiers. Neither do Boolean
        *    variables.
        *
-       * In GLSL ES, sampler types are also allowed.
+       * Section 4.5 (Precision and Precision Qualifiers) of the GLSL 1.30
+       * spec also says:
        *
-       * From page 87 of the GLSL ES spec:
-       *    "RESOLUTION: Allow sampler types to take a precision qualifier."
+       *     "Precision qualifiers are added for code portability with OpenGL
+       *     ES, not for functionality. They have the same syntax as in OpenGL
+       *     ES."
+       *
+       * Section 8 (Built-In Functions) of the GLSL ES 1.00 spec says:
+       *
+       *     "uniform lowp sampler2D sampler;
+       *     highp vec2 coord;
+       *     ...
+       *     lowp vec4 col = texture2D (sampler, coord);
+       *                                            // texture2D returns lowp"
+       *
+       * From this, we infer that GLSL 1.30 (and later) should allow precision
+       * qualifiers on sampler types just like float and integer types.
        */
       if (this->type->qualifier.precision != ast_precision_none
           && !var->type->is_float()
           && !var->type->is_integer()
           && !var->type->is_record()
-          && !(var->type->is_sampler() && state->es_shader)
+          && !var->type->is_sampler()
           && !(var->type->is_array()
                && (var->type->fields.array->is_float()
                    || var->type->fields.array->is_integer()))) {
 
          _mesa_glsl_error(&loc, state,
                           "precision qualifiers apply only to floating point"
-                          "%s types", state->es_shader ? ", integer, and sampler"
-						       : "and integer");
+                          ", integer and sampler types");
       }
 
       /* From page 17 (page 23 of the PDF) of the GLSL 1.20 spec: