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i965: Clamp "Maximum VP Index" to 1 when gl_ViewportIndex isn't written.

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fs_visitor::emit_urb_writes skips writing the VUE header for shaders
that don't write gl_PointSize, gl_Layer, or gl_ViewportIndex.  This
leaves their values uninitialized.  Kristian's nearby comment says:

"But often none of the special varyings that live there are written
 and in that case we can skip writing to the vue header, provided the
 corresponding state properly clamps the values further down the
 pipeline."

However, we were clamping gl_ViewportIndex to [0, 15], so we would end
up using a random viewport.  To fix this, detect when the shader doesn't
write gl_ViewportIndex, and clamp it to [0, 0].

The vec4 backend always writes zeros to the VUE header, so it doesn't
suffer from this problem.  With vec4-style HWord writes, we can write
the header and position together in a single message.  In the FS world,
we would need 4 extra MOVs of 0 and a longer message, or a separate
OWord write.  It's likely cheaper to just clamp the value.

Fixes DiRT Showdown and Bioshock Infinite, which only rendered half of
the screen - the lower left of two triangles.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93054
Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Kenneth Graunke 2016-05-07 17:30:02 -07:00
parent e74812dbfe
commit e0e7280db0
1 changed files with 10 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
src/mesa/drivers/dri/i965/gen6_clip_state.c
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@ -177,6 +177,11 @@ upload_clip_state(struct brw_context *brw)
if (!is_drawing_points(brw) && !is_drawing_lines(brw))
dw2 |= GEN6_CLIP_XY_TEST;
/* BRW_NEW_VUE_MAP_GEOM_OUT */
const int max_vp_index =
(brw->vue_map_geom_out.slots_valid & VARYING_BIT_VIEWPORT) != 0 ?
ctx->Const.MaxViewports : 1;
BEGIN_BATCH(4);
OUT_BATCH(_3DSTATE_CLIP << 16 | (4 - 2));
OUT_BATCH(dw1);
@ -186,7 +191,7 @@ upload_clip_state(struct brw_context *brw)
OUT_BATCH(U_FIXED(0.125, 3) << GEN6_CLIP_MIN_POINT_WIDTH_SHIFT |
U_FIXED(255.875, 3) << GEN6_CLIP_MAX_POINT_WIDTH_SHIFT |
(_mesa_geometric_layers(fb) > 0 ? 0 : GEN6_CLIP_FORCE_ZERO_RTAINDEX) |
((ctx->Const.MaxViewports - 1) & GEN6_CLIP_MAX_VP_INDEX_MASK));
((max_vp_index - 1) & GEN6_CLIP_MAX_VP_INDEX_MASK));
ADVANCE_BATCH();
}
@ -201,7 +206,8 @@ const struct brw_tracked_state gen6_clip_state = {
BRW_NEW_GEOMETRY_PROGRAM |
BRW_NEW_META_IN_PROGRESS |
BRW_NEW_PRIMITIVE |
BRW_NEW_RASTERIZER_DISCARD,
BRW_NEW_RASTERIZER_DISCARD |
BRW_NEW_VUE_MAP_GEOM_OUT,
},
.emit = upload_clip_state,
};
@ -218,7 +224,8 @@ const struct brw_tracked_state gen7_clip_state = {
BRW_NEW_GEOMETRY_PROGRAM |
BRW_NEW_META_IN_PROGRESS |
BRW_NEW_PRIMITIVE |
BRW_NEW_RASTERIZER_DISCARD,
BRW_NEW_RASTERIZER_DISCARD |
BRW_NEW_VUE_MAP_GEOM_OUT,
},
.emit = upload_clip_state,
};