Mesa (master): i965: Use true AA line distance on G45/Ironlake.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: b625bcc601a16fab1962f9ed569700d3d08738b9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b625bcc601a16fab1962f9ed569700d3d08738b9

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Wed Apr 26 14:28:49 2017 -0700

i965: Use true AA line distance on G45/Ironlake.

The original Broadwater and Crestline platforms computed antialiased
line distances using "manhattan" distance, aka a + b = c.  Eaglelake
and Cantiga added "true" distance, which apparently does something
like max(a, b) + min(a, b) / 4.  Not exactly "true", but at least
more accurate.

The G45 documentation indicates that the old manhattan distance setting
is "only for debug purposes" and should never be used.  The Ironlake
documentation no longer mentions AALINEDISTANCE_MANHATTAN, though it
does still contain the narrative about the feature.

At any rate, we should use the more accurate mode.

Reviewed-by: Plamena Manolova <plamena.manolova at intel.com>
Reviewed-by: Francisco Jerez <currojerez at riseup.net>

---

 src/mesa/drivers/dri/i965/brw_sf_state.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_sf_state.c b/src/mesa/drivers/dri/i965/brw_sf_state.c
index e919f5d14b..d50ceb1213 100644
--- a/src/mesa/drivers/dri/i965/brw_sf_state.c
+++ b/src/mesa/drivers/dri/i965/brw_sf_state.c
@@ -265,7 +265,7 @@ static void upload_sf_unit( struct brw_context *brw )
    /* _NEW_PROGRAM | _NEW_POINT */
    sf->sf7.use_point_size_state = !(ctx->VertexProgram.PointSizeEnabled ||
 				    ctx->Point._Attenuated);
-   sf->sf7.aa_line_distance_mode = 0;
+   sf->sf7.aa_line_distance_mode = brw->is_g4x || brw->gen == 5;
 
    /* might be BRW_NEW_PRIMITIVE if we have to adjust pv for polygons:
     * _NEW_LIGHT