[Mesa-dev] [PATCH v2] linker: Reject shaders that use too many varyings

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

Previously it was up to the driver or later code generator to reject
these shaders.  It turns out that nobody did this.

This will need changes to support geometry shaders.

NOTE: This is a candidate for the stable branches.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=37743
---
v2: My previous recollection of the GLSL spec was incorrect.  The same
input packing rule of one slot per variable float or vector is used
for both vertex inputs and fragment inputs.  This also removes the
stray debug printf.

 src/glsl/linker.cpp |   41 ++++++++++++++++++++++++++++++++++++-----
 1 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 255edc6..9b3d189 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1405,8 +1405,9 @@ demote_shader_inputs_and_outputs(gl_shader *sh, enum ir_variable_mode mode)
 }
 
 
-void
-assign_varying_locations(struct gl_shader_program *prog,
+bool
+assign_varying_locations(struct gl_context *ctx,
+			 struct gl_shader_program *prog,
 			 gl_shader *producer, gl_shader *consumer)
 {
    /* FINISHME: Set dynamically when geometry shader support is added. */
@@ -1462,6 +1463,8 @@ assign_varying_locations(struct gl_shader_program *prog,
       }
    }
 
+   unsigned float_components = 0;
+
    foreach_list(node, consumer->ir) {
       ir_variable *const var = ((ir_instruction *) node)->as_variable();
 
@@ -1492,8 +1495,32 @@ assign_varying_locations(struct gl_shader_program *prog,
 	  * value is written by the previous stage.
 	  */
 	 var->mode = ir_var_auto;
+      } else {
+	 /* The packing rules are used for vertex shader inputs are also used
+	  * for fragment shader inputs.
+	  */
+	 varying_vectors += count_attribute_slots(var->type);
       }
    }
+
+   if (ctx->API == API_OPENGLES2 || prog->Version == 100) {
+      if (varying_vectors > ctx->Const.MaxVarying) {
+	 linker_error_printf(prog, "shader uses too many varying vectors "
+			     "(%u > %u)\n",
+			     varying_vectors, ctx->Const.MaxVarying);
+	 return false;
+      }
+   } else {
+      const unsigned float_components = varying_vectors * 4;
+      if (float_components > ctx->Const.MaxVarying * 4) {
+	 linker_error_printf(prog, "shader uses too many varying components "
+			     "(%u > %u)\n",
+			     float_components, ctx->Const.MaxVarying * 4);
+	 return false;
+      }
+   }
+
+   return true;
 }
 
 
@@ -1666,9 +1693,13 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       if (prog->_LinkedShaders[i] == NULL)
 	 continue;
 
-      assign_varying_locations(prog,
-			       prog->_LinkedShaders[prev],
-			       prog->_LinkedShaders[i]);
+      if (!assign_varying_locations(ctx, prog,
+				    prog->_LinkedShaders[prev],
+				    prog->_LinkedShaders[i])) {
+	 prog->LinkStatus = false;
+	 goto done;
+      }
+
       prev = i;
    }
 
-- 
1.7.5.2