i965: Map GL_PATCHES to 3DPRIM_PATCHLIST_n.

Inspired by a patch by Fabian Bieler.

Fabian defined a _3DPRIM_PATCHLIST_0 macro (which isn't actually a valid
topology type); I instead chose to make a macro that takes an argument.
He also took the number of patch vertices from _mesa_prim (which was set
to ctx->TessCtrlProgram.patch_vertices) - I chose to use it directly to
avoid the need for the VBO patch.

v2: Change macro to 0x20 + (n - 1) instead of 0x1F + n to better match
    the documentation (suggested by Ian).

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/drivers/dri/i965/brw_defines.h

@@ -78,6 +78,8 @@
 #define _3DPRIM_LINESTRIP_BF      0x13
 #define _3DPRIM_LINESTRIP_CONT_BF 0x14
 #define _3DPRIM_TRIFAN_NOSTIPPLE  0x16
+#define _3DPRIM_PATCHLIST(n) ({ assert(n > 0 && n <= 32); 0x20 + (n - 1); })
+
 
 /* We use this offset to be able to pass native primitive types in struct
  * _mesa_prim::mode.  Native primitive types are BRW_PRIM_OFFSET +

src/mesa/drivers/dri/i965/brw_draw.c

@@ -140,9 +140,16 @@ brw_set_prim(struct brw_context *brw, const struct _mesa_prim *prim)
 static void
 gen6_set_prim(struct brw_context *brw, const struct _mesa_prim *prim)
 {
+   const struct gl_context *ctx = &brw->ctx;
+   uint32_t hw_prim;
+
    DBG("PRIM: %s\n", _mesa_enum_to_string(prim->mode));
 
-   const uint32_t hw_prim = get_hw_prim_for_gl_prim(prim->mode);
+   if (prim->mode == GL_PATCHES)
+      hw_prim = _3DPRIM_PATCHLIST(ctx->TessCtrlProgram.patch_vertices);
+   else
+      hw_prim = get_hw_prim_for_gl_prim(prim->mode);
+
    if (hw_prim != brw->primitive) {
       brw->primitive = hw_prim;
       brw->ctx.NewDriverState |= BRW_NEW_PRIMITIVE;