glsl: Simplify the interface to link_invalidate_variable_locations

The unit tests added in the previous commits prove some things about the
state of some internal data structures.  The most important of these is
that all built-in input and output variables have explicit_location
set.  This means that link_invalidate_variable_locations doesn't need to
know the range of non-generic shader inputs or outputs.  It can simply
reset location state depending on whether explicit_location is set.

There are two additional assumptions that were already implicit in the
code that comments now document.

  - ir_variable::is_unmatched_generic_inout is only used by the linker
    when connecting outputs from one shader stage to inputs of another
    shader stage.

  - Any varying that has explicit_location set must be a built-in.  This
    will be true until GL_ARB_separate_shader_objects is supported.

As a result, the input_base and output_base parameters to
link_invalidate_variable_locations are no longer necessary, and the code
for resetting locations and setting is_unmatched_generic_inout can be
simplified.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

3 files changed, 31 insertions, 44 deletions

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index bf96d60..b23c31a 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -366,8 +366,7 @@ parse_program_resource_name(const GLchar *name,
 
 
 void
-link_invalidate_variable_locations(exec_list *ir, int input_base,
-                                   int output_base)
+link_invalidate_variable_locations(exec_list *ir)
 {
    foreach_list(node, ir) {
       ir_variable *const var = ((ir_instruction *) node)->as_variable();
@@ -375,26 +374,30 @@ link_invalidate_variable_locations(exec_list *ir, int input_base,
       if (var == NULL)
          continue;
 
-      int base;
-      switch (var->mode) {
-      case ir_var_shader_in:
-         base = input_base;
-         break;
-      case ir_var_shader_out:
-         base = output_base;
-         break;
-      default:
-         continue;
-      }
-
-      /* Only assign locations for generic attributes / varyings / etc.
+      /* Only assign locations for variables that lack an explicit location.
+       * Explicit locations are set for all built-in variables, generic vertex
+       * shader inputs (via layout(location=...)), and generic fragment shader
+       * outputs (also via layout(location=...)).
        */
-      if ((var->location >= base) && !var->explicit_location)
+      if (!var->explicit_location) {
          var->location = -1;
+         var->location_frac = 0;
+      }
 
-      if ((var->location == -1) && !var->explicit_location) {
+      /* ir_variable::is_unmatched_generic_inout is used by the linker while
+       * connecting outputs from one stage to inputs of the next stage.
+       *
+       * There are two implicit assumptions here.  First, we assume that any
+       * built-in variable (i.e., non-generic in or out) will have
+       * explicit_location set.  Second, we assume that any generic in or out
+       * will not have explicit_location set.
+       *
+       * This second assumption will only be valid until
+       * GL_ARB_separate_shader_objects is supported.  When that extension is
+       * implemented, this function will need some modifications.
+       */
+      if (!var->explicit_location) {
          var->is_unmatched_generic_inout = 1;
-         var->location_frac = 0;
       } else {
          var->is_unmatched_generic_inout = 0;
       }
@@ -2217,18 +2220,15 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
    /* Mark all generic shader inputs and outputs as unpaired. */
    if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) {
       link_invalidate_variable_locations(
-            prog->_LinkedShaders[MESA_SHADER_VERTEX]->ir,
-            VERT_ATTRIB_GENERIC0, VARYING_SLOT_VAR0);
+            prog->_LinkedShaders[MESA_SHADER_VERTEX]->ir);
    }
    if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) {
       link_invalidate_variable_locations(
-            prog->_LinkedShaders[MESA_SHADER_GEOMETRY]->ir,
-            VARYING_SLOT_VAR0, VARYING_SLOT_VAR0);
+            prog->_LinkedShaders[MESA_SHADER_GEOMETRY]->ir);
    }
    if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] != NULL) {
       link_invalidate_variable_locations(
-            prog->_LinkedShaders[MESA_SHADER_FRAGMENT]->ir,
-            VARYING_SLOT_VAR0, FRAG_RESULT_DATA0);
+            prog->_LinkedShaders[MESA_SHADER_FRAGMENT]->ir);
    }
 
    /* FINISHME: The value of the max_attribute_index parameter is
diff --git a/src/glsl/linker.h b/src/glsl/linker.h
index 9915c38..887cd33 100644
--- a/src/glsl/linker.h
+++ b/src/glsl/linker.h
@@ -31,8 +31,7 @@ link_function_calls(gl_shader_program *prog, gl_shader *main,
 		    gl_shader **shader_list, unsigned num_shaders);
 
 extern void
-link_invalidate_variable_locations(exec_list *ir, int input_base,
-                                   int output_base);
+link_invalidate_variable_locations(exec_list *ir);
 
 extern void
 link_assign_uniform_locations(struct gl_shader_program *prog);
diff --git a/src/glsl/tests/invalidate_locations_test.cpp b/src/glsl/tests/invalidate_locations_test.cpp
index cded1d5..f70dc6f 100644
--- a/src/glsl/tests/invalidate_locations_test.cpp
+++ b/src/glsl/tests/invalidate_locations_test.cpp
@@ -72,9 +72,7 @@ TEST_F(invalidate_locations, simple_vertex_in_generic)
 
    ir.push_tail(var);
 
-   link_invalidate_variable_locations(&ir,
-                                      VERT_ATTRIB_GENERIC0,
-                                      VARYING_SLOT_VAR0);
+   link_invalidate_variable_locations(&ir);
 
    EXPECT_EQ(-1, var->location);
    EXPECT_EQ(0u, var->location_frac);
@@ -97,9 +95,7 @@ TEST_F(invalidate_locations, explicit_location_vertex_in_generic)
 
    ir.push_tail(var);
 
-   link_invalidate_variable_locations(&ir,
-                                      VERT_ATTRIB_GENERIC0,
-                                      VARYING_SLOT_VAR0);
+   link_invalidate_variable_locations(&ir);
 
    EXPECT_EQ(VERT_ATTRIB_GENERIC0, var->location);
    EXPECT_EQ(0u, var->location_frac);
@@ -123,9 +119,7 @@ TEST_F(invalidate_locations, explicit_location_frac_vertex_in_generic)
 
    ir.push_tail(var);
 
-   link_invalidate_variable_locations(&ir,
-                                      VERT_ATTRIB_GENERIC0,
-                                      VARYING_SLOT_VAR0);
+   link_invalidate_variable_locations(&ir);
 
    EXPECT_EQ(VERT_ATTRIB_GENERIC0, var->location);
    EXPECT_EQ(2u, var->location_frac);
@@ -148,9 +142,7 @@ TEST_F(invalidate_locations, vertex_in_builtin)
 
    ir.push_tail(var);
 
-   link_invalidate_variable_locations(&ir,
-                                      VERT_ATTRIB_GENERIC0,
-                                      VARYING_SLOT_VAR0);
+   link_invalidate_variable_locations(&ir);
 
    EXPECT_EQ(VERT_ATTRIB_POS, var->location);
    EXPECT_EQ(0u, var->location_frac);
@@ -172,9 +164,7 @@ TEST_F(invalidate_locations, simple_vertex_out_generic)
 
    ir.push_tail(var);
 
-   link_invalidate_variable_locations(&ir,
-                                      VERT_ATTRIB_GENERIC0,
-                                      VARYING_SLOT_VAR0);
+   link_invalidate_variable_locations(&ir);
 
    EXPECT_EQ(-1, var->location);
    EXPECT_EQ(0u, var->location_frac);
@@ -197,9 +187,7 @@ TEST_F(invalidate_locations, vertex_out_builtin)
 
    ir.push_tail(var);
 
-   link_invalidate_variable_locations(&ir,
-                                      VERT_ATTRIB_GENERIC0,
-                                      VARYING_SLOT_VAR0);
+   link_invalidate_variable_locations(&ir);
 
    EXPECT_EQ(VARYING_SLOT_COL0, var->location);
    EXPECT_EQ(0u, var->location_frac);