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 <[email protected]>

Signed-off-by: Anuj Phogat <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>
Cc: <[email protected]>

1 files changed, 21 insertions, 8 deletions

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 192130a99b8..52059e4bfb3 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -3132,32 +3132,45 @@ 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: