Mesa (master): svga: avoid provoking vertex conversion when possible

[Brian Paul]

Module: Mesa
Branch: master
Commit: 129d34da494840628b2bb1cbb6397d50dab3c999
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=129d34da494840628b2bb1cbb6397d50dab3c999

Author: Brian Paul <brianp at vmware.com>
Date:   Fri Oct 16 16:12:19 2015 -0600

svga: avoid provoking vertex conversion when possible

Provoking vertex comes into play when doing flat shading.  But if we know
that all fragments in a primitive are the same color, the provoking vertex
doesn't matter.  Check for that case and use whichever provoking vertex
convention is supported by the device.

This avoids generating an index buffer to do the PV conversion.

Reviewed-by: Charmaine Lee <charmainel at vmware.com>
Reviewed-by: José Fonseca <jfonseca at vmware.com>

---

 src/gallium/drivers/svga/svga_draw_arrays.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/gallium/drivers/svga/svga_draw_arrays.c b/src/gallium/drivers/svga/svga_draw_arrays.c
index 5635411..e4d7764 100644
--- a/src/gallium/drivers/svga/svga_draw_arrays.c
+++ b/src/gallium/drivers/svga/svga_draw_arrays.c
@@ -32,6 +32,7 @@
 #include "svga_draw.h"
 #include "svga_draw_private.h"
 #include "svga_context.h"
+#include "svga_shader.h"
 
 
 #define DBG 0
@@ -206,6 +207,18 @@ svga_hwtnl_draw_arrays(struct svga_hwtnl *hwtnl,
    unsigned gen_prim, gen_size, gen_nr, gen_type;
    u_generate_func gen_func;
    enum pipe_error ret = PIPE_OK;
+   unsigned api_pv = hwtnl->api_pv;
+   struct svga_context *svga = hwtnl->svga;
+
+   if (svga->curr.rast->templ.flatshade &&
+       svga->state.hw_draw.fs->constant_color_output) {
+      /* The fragment color is a constant, not per-vertex so the whole
+       * primitive will be the same color (except for possible blending).
+       * We can ignore the current provoking vertex state and use whatever
+       * the hardware wants.
+       */
+      api_pv = hwtnl->hw_pv;
+   }
 
    if (hwtnl->api_fillmode != PIPE_POLYGON_MODE_FILL &&
        prim >= PIPE_PRIM_TRIANGLES) {
@@ -226,7 +239,7 @@ svga_hwtnl_draw_arrays(struct svga_hwtnl *hwtnl,
                                    prim,
                                    start,
                                    count,
-                                   hwtnl->api_pv,
+                                   api_pv,
                                    hwtnl->hw_pv,
                                    &gen_prim, &gen_size, &gen_nr, &gen_func);
    }