[Mesa-dev] [PATCH v2 6/7] i965: support gl_InvocationID for gen7

[Jordan Justen]

Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
---
 src/mesa/drivers/dri/i965/brw_defines.h           |  5 +++++
 src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp | 24 ++++++++++++++++++++---
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
index 7f4cd10..5fe1aba 100644
--- a/src/mesa/drivers/dri/i965/brw_defines.h
+++ b/src/mesa/drivers/dri/i965/brw_defines.h
@@ -1500,6 +1500,11 @@ enum brw_message_target {
 # define BRW_GS_EDGE_INDICATOR_0			(1 << 8)
 # define BRW_GS_EDGE_INDICATOR_1			(1 << 9)
 
+/* GS Thread Payload
+ */
+/* R0 */
+# define GEN7_GS_PAYLOAD_INSTANCE_ID_SHIFT		27
+
 /* 3DSTATE_GS "Output Vertex Size" has an effective maximum of 62.  It's
  * counted in multiples of 16 bytes.
  */
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
index 40743cc..12e137c 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
@@ -51,9 +51,27 @@ vec4_gs_visitor::vec4_gs_visitor(struct brw_context *brw,
 dst_reg *
 vec4_gs_visitor::make_reg_for_system_value(ir_variable *ir)
 {
-   /* Geometry shaders don't use any system values. */
-   assert(!"Unreached");
-   return NULL;
+   dst_reg *reg;
+   src_reg r0(retype(brw_vec4_grf(0, 0), BRW_REGISTER_TYPE_UD));
+
+   switch (ir->data.location) {
+   case SYSTEM_VALUE_INVOCATION_ID:
+      this->current_annotation = "initialize gl_InvocationID";
+
+      reg = new(mem_ctx) dst_reg(this, ir->type);
+
+      /* Copy and shift gen7 instance id from R0 into the
+       * gl_InvocationID register.
+       */
+      emit(SHR(*reg, src_reg(r0),
+               (uint32_t) GEN7_GS_PAYLOAD_INSTANCE_ID_SHIFT));
+      break;
+   default:
+      assert(!"not reached");
+      break;
+   }
+
+   return reg;
 }
 
 
-- 
1.8.5.3