linker: Reject shaders that use too many varyings

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
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 255edc6a76f179d2198805c8db0e0b8c780a7958..b6479e7a3a4e5084a6c6ceb9dc4dfd8334728367 100644 (file)
--- 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 varying_vectors = 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;
    }