Mesa (master): i965: Add scalar GS input lowering code.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: c9541a74e4d179ad844bdf8af1e3de541c5b14c2
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=c9541a74e4d179ad844bdf8af1e3de541c5b14c2

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Wed Sep 23 20:52:19 2015 -0700

i965: Add scalar GS input lowering code.

We really ought to compute the VUE map at link time and stash it, rather
than recomputing it here, but with the mess of program structures I
wasn't sure where to put it.  We can improve that later.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Kristian Høgsberg <krh at bitplanet.net>

---

 src/mesa/drivers/dri/i965/brw_nir.c |   44 +++++++++++++++++++++++++++++++----
 1 file changed, 39 insertions(+), 5 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_nir.c b/src/mesa/drivers/dri/i965/brw_nir.c
index 11f1113..a7a5eb5 100644
--- a/src/mesa/drivers/dri/i965/brw_nir.c
+++ b/src/mesa/drivers/dri/i965/brw_nir.c
@@ -56,7 +56,8 @@ remap_vs_attrs(nir_block *block, void *closure)
 }
 
 static void
-brw_nir_lower_inputs(nir_shader *nir, bool is_scalar)
+brw_nir_lower_inputs(const struct brw_device_info *devinfo,
+                     nir_shader *nir, bool is_scalar)
 {
    switch (nir->stage) {
    case MESA_SHADER_VERTEX:
@@ -90,11 +91,43 @@ brw_nir_lower_inputs(nir_shader *nir, bool is_scalar)
          }
       }
       break;
-   case MESA_SHADER_GEOMETRY:
-      foreach_list_typed(nir_variable, var, node, &nir->inputs) {
-         var->data.driver_location = var->data.location;
+   case MESA_SHADER_GEOMETRY: {
+      if (!is_scalar) {
+         foreach_list_typed(nir_variable, var, node, &nir->inputs) {
+            var->data.driver_location = var->data.location;
+         }
+      } else {
+         /* The GLSL linker will have already matched up GS inputs and
+          * the outputs of prior stages.  The driver does extend VS outputs
+          * in some cases, but only for legacy OpenGL or Gen4-5 hardware,
+          * neither of which offer geometry shader support.  So we can
+          * safely ignore that.
+          *
+          * For SSO pipelines, we use a fixed VUE map layout based on variable
+          * locations, so we can rely on rendezvous-by-location to make this
+          * work.
+          *
+          * However, we need to ignore VARYING_SLOT_PRIMITIVE_ID, as it's not
+          * written by previous stages and shows up via payload magic.
+          */
+         struct brw_vue_map input_vue_map;
+         GLbitfield64 inputs_read =
+            nir->info.inputs_read & ~VARYING_BIT_PRIMITIVE_ID;
+         brw_compute_vue_map(devinfo, &input_vue_map, inputs_read,
+                             nir->info.separate_shader);
+
+         /* Start with the slot for the variable's base. */
+         foreach_list_typed(nir_variable, var, node, &nir->inputs) {
+            assert(input_vue_map.varying_to_slot[var->data.location] != -1);
+            var->data.driver_location =
+               input_vue_map.varying_to_slot[var->data.location];
+         }
+
+         /* Inputs are stored in vec4 slots, so use type_size_vec4(). */
+         nir_lower_io(nir, nir_var_shader_in, type_size_vec4);
       }
       break;
+   }
    case MESA_SHADER_FRAGMENT:
       assert(is_scalar);
       nir_assign_var_locations(&nir->inputs, &nir->num_inputs,
@@ -187,6 +220,7 @@ brw_create_nir(struct brw_context *brw,
                bool is_scalar)
 {
    struct gl_context *ctx = &brw->ctx;
+   const struct brw_device_info *devinfo = brw->intelScreen->devinfo;
    const nir_shader_compiler_options *options =
       ctx->Const.ShaderCompilerOptions[stage].NirOptions;
    static const nir_lower_tex_options tex_options = {
@@ -230,7 +264,7 @@ brw_create_nir(struct brw_context *brw,
    /* Get rid of split copies */
    nir_optimize(nir, is_scalar);
 
-   brw_nir_lower_inputs(nir, is_scalar);
+   brw_nir_lower_inputs(devinfo, nir, is_scalar);
    brw_nir_lower_outputs(nir, is_scalar);
    nir_assign_var_locations(&nir->uniforms,
                             &nir->num_uniforms,