[Mesa-dev] [PATCH 1/9] i965/vec4: Don't emit MOVs for unused URB slots.

[Matt Turner]

Otherwise we'd emit a MOV from the null register (which isn't allowed).

Helps 24 programs in shader-db (the geometry shaders in GSCloth):

instructions in affected programs:     302 -> 262 (-13.25%)
---
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp    | 18 +++++++++++++-----
 src/mesa/drivers/dri/i965/brw_vec4_vs_visitor.cpp |  2 +-
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index f891910..c39f97e 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -1221,6 +1221,9 @@ vec4_visitor::emit_untyped_surface_read(unsigned surf_index, dst_reg dst,
 void
 vec4_visitor::emit_ndc_computation()
 {
+   if (output_reg[VARYING_SLOT_POS].file == BAD_FILE)
+      return;
+
    /* Get the position */
    src_reg pos = src_reg(output_reg[VARYING_SLOT_POS]);
 
@@ -1286,7 +1289,8 @@ vec4_visitor::emit_psiz_and_flags(dst_reg reg)
        * Later, clipping will detect ucp[6] and ensure the primitive is
        * clipped against all fixed planes.
        */
-      if (devinfo->has_negative_rhw_bug) {
+      if (devinfo->has_negative_rhw_bug &&
+          output_reg[BRW_VARYING_SLOT_NDC].file != BAD_FILE) {
          src_reg ndc_w = src_reg(output_reg[BRW_VARYING_SLOT_NDC]);
          ndc_w.swizzle = BRW_SWIZZLE_WWWW;
          emit(CMP(dst_null_f(), ndc_w, src_reg(0.0f), BRW_CONDITIONAL_L));
@@ -1334,8 +1338,10 @@ vec4_visitor::emit_generic_urb_slot(dst_reg reg, int varying)
    assert(varying < VARYING_SLOT_MAX);
    assert(output_reg[varying].type == reg.type);
    current_annotation = output_reg_annotation[varying];
-   /* Copy the register, saturating if necessary */
-   return emit(MOV(reg, src_reg(output_reg[varying])));
+   if (output_reg[varying].file != BAD_FILE)
+      return emit(MOV(reg, src_reg(output_reg[varying])));
+   else
+      return NULL;
 }
 
 void
@@ -1354,11 +1360,13 @@ vec4_visitor::emit_urb_slot(dst_reg reg, int varying)
    }
    case BRW_VARYING_SLOT_NDC:
       current_annotation = "NDC";
-      emit(MOV(reg, src_reg(output_reg[BRW_VARYING_SLOT_NDC])));
+      if (output_reg[BRW_VARYING_SLOT_NDC].file != BAD_FILE)
+         emit(MOV(reg, src_reg(output_reg[BRW_VARYING_SLOT_NDC])));
       break;
    case VARYING_SLOT_POS:
       current_annotation = "gl_Position";
-      emit(MOV(reg, src_reg(output_reg[VARYING_SLOT_POS])));
+      if (output_reg[VARYING_SLOT_POS].file != BAD_FILE)
+         emit(MOV(reg, src_reg(output_reg[VARYING_SLOT_POS])));
       break;
    case VARYING_SLOT_EDGE:
       /* This is present when doing unfilled polygons.  We're supposed to copy
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_vs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_vs_visitor.cpp
index 485a80e..5dd4f98 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_vs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_vs_visitor.cpp
@@ -217,7 +217,7 @@ vec4_vs_visitor::emit_urb_slot(dst_reg reg, int varying)
        * shader.
        */
       vec4_instruction *inst = emit_generic_urb_slot(reg, varying);
-      if (key->clamp_vertex_color)
+      if (inst && key->clamp_vertex_color)
          inst->saturate = true;
       break;
    }
-- 
2.4.9