[Mesa-dev] [PATCH] i965: Use vec4 vs shader path in spill cases.

[Bish, Jim]

For BDW and newer hardware, vertex shaders can be dispatched
using simd8 scalars, but when spills occur performance will
be impacted.

Fixes spec at glsl-1.10@execution at varying-packing@simple by falling back
to vec4x2 dispatch. There is another issue with simd8 dispatch which
will be addressed later.

Bugzill : https://bugs.freedesktop.org/show_bug.cgi?id=89055
---
 src/mesa/drivers/dri/i965/brw_vec4.cpp | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index 5a9c3f5..6ea9f92 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1909,26 +1909,34 @@ brw_vs_emit(struct brw_context *brw,
 
          return NULL;
       }
-
-      fs_generator g(brw, mem_ctx, (void *) &c->key, &prog_data->base.base,
+      
+      if (!v.spilled_any_registers) {
+         fs_generator g(brw, mem_ctx, (void *) &c->key, &prog_data->base.base,
                      &c->vp->program.Base, v.promoted_constants,
                      v.runtime_check_aads_emit, "VS");
-      if (INTEL_DEBUG & DEBUG_VS) {
-         char *name;
-         if (prog) {
-            name = ralloc_asprintf(mem_ctx, "%s vertex shader %d",
+         if (INTEL_DEBUG & DEBUG_VS) {
+            char *name;
+            if (prog) {
+               name = ralloc_asprintf(mem_ctx, "%s vertex shader %d",
                                    prog->Label ? prog->Label : "unnamed",
                                    prog->Name);
-         } else {
-            name = ralloc_asprintf(mem_ctx, "vertex program %d",
+            } else {
+               name = ralloc_asprintf(mem_ctx, "vertex program %d",
                                    c->vp->program.Base.Id);
+            }
+            g.enable_debug(name);
          }
-         g.enable_debug(name);
-      }
-      g.generate_code(v.cfg, 8);
-      assembly = g.get_assembly(final_assembly_size);
+         g.generate_code(v.cfg, 8);
+         assembly = g.get_assembly(final_assembly_size);
 
-      c->base.last_scratch = v.last_scratch;
+         c->base.last_scratch = v.last_scratch;
+      } else {
+         /*
+          * Clean up from previous attempt to use simd8 dispatch
+          */
+         brw->scalar_vs = false;
+         prog_data->base.base.total_scratch = 0; /* reset */         
+      }
    }
 
    if (!assembly) {
-- 
2.1.4