Mesa (master): i965: Handle rasterizer discard in the clipper rather than SOL on Gen7.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: d1e4e9960cbdfce6078cdc377809ea76c2eb7078
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d1e4e9960cbdfce6078cdc377809ea76c2eb7078

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Thu May 16 19:25:14 2013 -0700

i965: Handle rasterizer discard in the clipper rather than SOL on Gen7.

In order to implement the GL_PRIMITIVES_GENERATED query in a sane
fashion on our hardware, we can't discard primitives until the clipper.
The patch after next explains the rationale.

By setting the clipper to REJECT_ALL mode, all primitives get thrown away,
so rendering is still appropriately disabled.

This may negatively impact performance in the rasterizer discard case,
but it's unclear how much and this hasn't been observed to be a
bottleneck in any application we've looked at.  The clipper is the very
next stage in the pipeline, so I don't think it will be terrible.

v2: Add a perf_debug; resolve rebase conflicts on the brw dirty flags.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Eric Anholt <eric at anholt.net>
Reviewed-by: Paul Berry <stereotype441 at gmail.com>

---

 src/mesa/drivers/dri/i965/gen7_clip_state.c |   11 ++++++++++-
 src/mesa/drivers/dri/i965/gen7_sol_state.c  |    7 +------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/gen7_clip_state.c b/src/mesa/drivers/dri/i965/gen7_clip_state.c
index 7c9f6c1..aae7895 100644
--- a/src/mesa/drivers/dri/i965/gen7_clip_state.c
+++ b/src/mesa/drivers/dri/i965/gen7_clip_state.c
@@ -102,6 +102,13 @@ upload_clip_state(struct brw_context *brw)
       dw2 |= GEN6_CLIP_GB_TEST;
    }
 
+   /* BRW_NEW_RASTERIZER_DISCARD */
+   if (ctx->RasterDiscard) {
+      dw2 |= GEN6_CLIP_MODE_REJECT_ALL;
+      perf_debug("Rasterizer discard is currently implemented via the clipper; "
+                 "using the SOL unit may be faster.");
+   }
+
    BEGIN_BATCH(4);
    OUT_BATCH(_3DSTATE_CLIP << 16 | (4 - 2));
    OUT_BATCH(dw1);
@@ -122,7 +129,9 @@ const struct brw_tracked_state gen7_clip_state = {
                 _NEW_POLYGON |
                 _NEW_LIGHT |
                 _NEW_TRANSFORM),
-      .brw   = BRW_NEW_CONTEXT | BRW_NEW_META_IN_PROGRESS,
+      .brw   = BRW_NEW_CONTEXT |
+               BRW_NEW_META_IN_PROGRESS |
+               BRW_NEW_RASTERIZER_DISCARD,
       .cache = CACHE_NEW_WM_PROG
    },
    .emit = upload_clip_state,
diff --git a/src/mesa/drivers/dri/i965/gen7_sol_state.c b/src/mesa/drivers/dri/i965/gen7_sol_state.c
index f570336..1e484dc 100644
--- a/src/mesa/drivers/dri/i965/gen7_sol_state.c
+++ b/src/mesa/drivers/dri/i965/gen7_sol_state.c
@@ -195,10 +195,6 @@ upload_3dstate_streamout(struct brw_context *brw, bool active,
    uint32_t dw1 = 0, dw2 = 0;
    int i;
 
-   /* BRW_NEW_RASTERIZER_DISCARD */
-   if (ctx->RasterDiscard)
-      dw1 |= SO_RENDERING_DISABLE;
-
    if (active) {
       int urb_entry_read_offset = 0;
       int urb_entry_read_length = (vue_map->num_slots + 1) / 2 -
@@ -267,8 +263,7 @@ const struct brw_tracked_state gen7_sol_state = {
       .brw   = (BRW_NEW_BATCH |
 		BRW_NEW_VERTEX_PROGRAM |
                 BRW_NEW_VUE_MAP_GEOM_OUT |
-                BRW_NEW_TRANSFORM_FEEDBACK |
-                BRW_NEW_RASTERIZER_DISCARD)
+                BRW_NEW_TRANSFORM_FEEDBACK)
    },
    .emit = upload_sol_state,
 };