[Mesa-dev] [PATCH 09/10] i965: Handle rasterizer discard in the clipper rather than GS on Gen6.

[Paul Berry]

On 17 May 2013 10:18, Kenneth Graunke <kenneth at whitecape.org> wrote:

> This has more of a negative impact than the previous patch, as on Gen6
> passing primitives through to the clipper means we actually have to make
> the GS thread write them to the URB.
>
> I don't see another good solution though, and rasterizer discard is not
> the most common of cases, so hopefully it won't be too terrible.
>
> Cc: Eric Anholt <eric at anholt.net>
> Cc: Paul Berry <stereotype441 at gmail.com>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/brw_gs.c          |  9 +--------
>  src/mesa/drivers/dri/i965/brw_gs_emit.c     | 30
> -----------------------------
>  src/mesa/drivers/dri/i965/gen6_clip_state.c |  6 +++++-
>  3 files changed, 6 insertions(+), 39 deletions(-)
>
> This patch prevents breakage in patch 10.  See patch 10 for the rationale.
>

This patch removes the last use of brw_gs_prog_key::rasterizer_discard.
Let's remove that unused field to avoid future confusion.

With that change, this patch is:

Reviewed-by: Paul Berry <stereotype441 at gmail.com>


>
> diff --git a/src/mesa/drivers/dri/i965/brw_gs.c
> b/src/mesa/drivers/dri/i965/brw_gs.c
> index a432b76..f354dd9 100644
> --- a/src/mesa/drivers/dri/i965/brw_gs.c
> +++ b/src/mesa/drivers/dri/i965/brw_gs.c
> @@ -214,12 +214,6 @@ static void populate_key( struct brw_context *brw,
>
> swizzle_for_offset[linked_xfb_info->Outputs[i].ComponentOffset];
>           }
>        }
> -      /* On Gen6, GS is also used for rasterizer discard. */
> -      /* BRW_NEW_RASTERIZER_DISCARD */
> -      if (ctx->RasterDiscard) {
> -         key->need_gs_prog = true;
> -         key->rasterizer_discard = true;
> -      }
>     } else {
>        /* Pre-gen6, GS is used to transform QUADLIST, QUADSTRIP, and
> LINELOOP
>         * into simpler primitives.
> @@ -259,8 +253,7 @@ const struct brw_tracked_state brw_gs_prog = {
>     .dirty = {
>        .mesa  = (_NEW_LIGHT),
>        .brw   = (BRW_NEW_PRIMITIVE |
> -                BRW_NEW_TRANSFORM_FEEDBACK |
> -                BRW_NEW_RASTERIZER_DISCARD),
> +                BRW_NEW_TRANSFORM_FEEDBACK),
>        .cache = CACHE_NEW_VS_PROG
>     },
>     .emit = brw_upload_gs_prog
> diff --git a/src/mesa/drivers/dri/i965/brw_gs_emit.c
> b/src/mesa/drivers/dri/i965/brw_gs_emit.c
> index 87ff9f0..cbfc6aa 100644
> --- a/src/mesa/drivers/dri/i965/brw_gs_emit.c
> +++ b/src/mesa/drivers/dri/i965/brw_gs_emit.c
> @@ -201,28 +201,6 @@ static void brw_gs_emit_vue(struct brw_gs_compile *c,
>  }
>
>  /**
> - * De-allocate the URB entry that was previously allocated to this thread
> - * (without writing any vertex data to it), and terminate the thread.
>  This is
> - * used to implement RASTERIZER_DISCARD functionality.
> - */
> -static void brw_gs_terminate(struct brw_gs_compile *c)
> -{
> -   struct brw_compile *p = &c->func;
> -   brw_urb_WRITE(p,
> -                 retype(brw_null_reg(), BRW_REGISTER_TYPE_UD), /* dest */
> -                 0, /* msg_reg_nr */
> -                 c->reg.header, /* src0 */
> -                 false, /* allocate */
> -                 false, /* used */
> -                 1, /* msg_length */
> -                 0, /* response_length */
> -                 true, /* eot */
> -                 true, /* writes_complete */
> -                 0, /* offset */
> -                 BRW_URB_SWIZZLE_NONE);
> -}
> -
> -/**
>   * Send an FF_SYNC message to ensure that all previously spawned GS
> threads
>   * have finished sending primitives down the pipeline, and to allocate a
> URB
>   * entry for the first output vertex.  Only needed when
> intel->needs_ff_sync
> @@ -484,14 +462,6 @@ gen6_sol_program(struct brw_gs_compile *c, struct
> brw_gs_prog_key *key,
>
>     brw_gs_ff_sync(c, 1);
>
> -   /* If RASTERIZER_DISCARD is enabled, we have nothing further to do, so
> -    * release the URB that was just allocated, and terminate the thread.
> -    */
> -   if (key->rasterizer_discard) {
> -      brw_gs_terminate(c);
> -      return;
> -   }
> -
>     brw_gs_overwrite_header_dw2_from_r0(c);
>     switch (num_verts) {
>     case 1:
> diff --git a/src/mesa/drivers/dri/i965/gen6_clip_state.c
> b/src/mesa/drivers/dri/i965/gen6_clip_state.c
> index 1811a3f..b5e22dc 100644
> --- a/src/mesa/drivers/dri/i965/gen6_clip_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_clip_state.c
> @@ -77,6 +77,10 @@ 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;
> +
>     BEGIN_BATCH(4);
>     OUT_BATCH(_3DSTATE_CLIP << 16 | (4 - 2));
>     OUT_BATCH(dw1);
> @@ -94,7 +98,7 @@ upload_clip_state(struct brw_context *brw)
>  const struct brw_tracked_state gen6_clip_state = {
>     .dirty = {
>        .mesa  = _NEW_TRANSFORM | _NEW_LIGHT | _NEW_BUFFERS,
> -      .brw   = (BRW_NEW_CONTEXT),
> +      .brw   = BRW_NEW_CONTEXT | BRW_NEW_RASTERIZER_DISCARD,
>        .cache = CACHE_NEW_WM_PROG
>     },
>     .emit = upload_clip_state,
> --
> 1.8.2.3
>
>
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