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i965/clear: Quantize the depth clear value based on the format 

In f9fd976e8a we changed the clear value to be stored as an
isl_color_value.  This had the side-effect same clear value check is now
happening directly between the f32[0] field of the isl_color_value and
ctx->Depth.Clear.  This isn't what we want for two reasons.  One is that
the comparison happens in floating point even for Z16 and Z24 formats.
Worse than that, ctx->Depth.Clear is a double so, even for 32-bit float
formats, we were comparing as doubles and not floats.  This means that
the test basically always fails for anything other than 0.0f and 1.0f.
This caused a slight performance regression in Lightsmark 2008 because
it was using a depth clear value of 0.999 which can't be stored in a
32-bit float so we were doing unneeded resolves.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Bugzilla: https://bugs.freedesktop.org/101678
Cc: "17.2" <mesa-stable@lists.freedesktop.org>
This commit is contained in:
Jason Ekstrand 2017-08-19 20:31:03 -07:00
parent 3c9ed70d92
commit 0ae9ce0f29
1 changed files with 12 additions and 2 deletions
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14
src/mesa/drivers/dri/i965/brw_clear.c
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@ -159,12 +159,22 @@ brw_fast_clear_depth(struct gl_context *ctx)
break;
}
/* Quantize the clear value to what can be stored in the actual depth
* buffer. This makes the following check more accurate because it now
* checks if the actual depth bits will match. It also prevents us from
* getting a too-accurate depth value during depth testing or when sampling
* with HiZ enabled.
*/
float clear_value =
mt->format == MESA_FORMAT_Z_FLOAT32 ? ctx->Depth.Clear :
(unsigned)(ctx->Depth.Clear * fb->_DepthMax) / (float)fb->_DepthMax;
const uint32_t num_layers = depth_att->Layered ? depth_irb->layer_count : 1;
/* If we're clearing to a new clear value, then we need to resolve any clear
* flags out of the HiZ buffer into the real depth buffer.
*/
if (mt->fast_clear_color.f32[0] != ctx->Depth.Clear) {
if (mt->fast_clear_color.f32[0] != clear_value) {
for (uint32_t level = mt->first_level; level <= mt->last_level; level++) {
if (!intel_miptree_level_has_hiz(mt, level))
continue;
@ -201,7 +211,7 @@ brw_fast_clear_depth(struct gl_context *ctx)
}
}
mt->fast_clear_color.f32[0] = ctx->Depth.Clear;
mt->fast_clear_color.f32[0] = clear_value;
}
bool need_clear = false;