[Mesa-dev] [PATCH v2 5/7] anv/pipeline: Be smarter about depth/stencil state
Jason Ekstrand
jason at jlekstrand.net
Mon Feb 13 19:19:52 UTC 2017
On Mon, Feb 13, 2017 at 11:14 AM, Nanley Chery <nanleychery at gmail.com>
wrote:
> On Fri, Feb 10, 2017 at 09:26:52PM -0800, Jason Ekstrand wrote:
> > On Fri, Feb 10, 2017 at 5:29 PM, Nanley Chery <nanleychery at gmail.com>
> wrote:
> >
> > > On Fri, Feb 10, 2017 at 03:31:32PM -0800, Jason Ekstrand wrote:
> > > > On Fri, Feb 10, 2017 at 3:18 PM, Nanley Chery <nanleychery at gmail.com
> >
> > > wrote:
> > > >
> > > > > On Fri, Feb 10, 2017 at 02:55:42PM -0800, Nanley Chery wrote:
> > > > > > On Fri, Feb 10, 2017 at 11:02:19AM -0800, Jason Ekstrand wrote:
> > > > > > > It's a bit hard to measure because it almost gets lost in the
> > > noise,
> > > > > > > but this seemed to help Dota 2 by a percent or two on my
> Broadwell
> > > > > > > GT3e desktop.
> > > > > > >
> > > > > > > Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> > > > > > > ---
> > > > > > > src/intel/vulkan/genX_pipeline.c | 171
> > > ++++++++++++++++++++++++++++++
> > > > > +--------
> > > > > > > 1 file changed, 137 insertions(+), 34 deletions(-)
> > > > > > >
> > > > > > > diff --git a/src/intel/vulkan/genX_pipeline.c
> > > b/src/intel/vulkan/genX_
> > > > > pipeline.c
> > > > > > > index 71b9e30..d2af8b9 100644
> > > > > > > --- a/src/intel/vulkan/genX_pipeline.c
> > > > > > > +++ b/src/intel/vulkan/genX_pipeline.c
> > > > > > > @@ -638,6 +638,133 @@ static const uint32_t
> vk_to_gen_stencil_op[]
> > > = {
> > > > > > > [VK_STENCIL_OP_DECREMENT_AND_WRAP] =
> STENCILOP_DECR,
> > > > > > > };
> > > > > > >
> > > > > > > +static bool
> > > > > > > +may_write_stencil_face(const VkStencilOpState *face,
> > > > > > > + VkCompareOp depthCompareOp)
> > > > > > > +{
> > > > > >
> > > > > > This function triggers some false negatives. One example is
> > > > > >
> > > > > > face->compareOp == VK_COMPARE_OP_GREATER &&
> > > > > > face->depthFailOp == VK_STENCIL_OP_KEEP &&
> > > > > > face->passOp == VK_STENCIL_OP_KEEP &&
> > > > > > face->failOp == VK_STENCIL_OP_INVERT &&
> > > > > > depthCompareOp == don't care;
> > > > > >
> > > > > > This function returns false even though a stencil write occurs
> if the
> > > > > > stencil test results in a fail.
> > > > >
> > > > > Thanks for pointing out in the office that this actually isn't a
> false
> > > > > negative. This function is correct, but I still think it could be
> > > > > simplified. I really needed a visual to evaluate it as it
> currently is
> > > > > written.
> > > > >
> > > >
> > > > There is a way I could write it that may be clearer. How about:
> > > >
> > > > may_write_stencil_face(const VkStencilOpState *face,
> > > > VkCompareOp depthCompareOp)
> > > > {
> > > > /* If compareOp is ALWAYS, then failOp doesn't matter */
> > > > if (face->compareOp == VK_COMPARE_OP_ALWAYS)
> > > > face->failOp = VK_STENCIL_OP_KEEP;
> > > >
> > > > if (face->compareOp == VK_COMPARE_OP_NEVER ||
> > >
> > > Why does the depth compare op independently impact the stencil op?
> > > Did you mean && instead of ||?
> > >
> >
> > Perhaps it would help if I explained the way that I'm reasoning about
> > things a bit better.
> >
> > In the first case (above), if compareOp is ALWAYS then the stencil test
> > will never fail so the failOp doesn't matter. We can set it to KEEP or
> > whatever else we like but KEEP is the most convenient.
> >
> > The second case is a bit more complicated. Here we're looking at the
> > stencil+depth pass op. In order for this to trigger, both the depth and
> > the stencil test have to pass. If either compare function is NEVER then
> at
> > least one of them will always fail and we'll never trigger the passOp.
> >
> > In the third case, depthFailOp gets taken if stencil passes but depth
> > fails. Again, if compareOp == NEVER or depthCompareOp == ALWAYS, then
> this
> > case cannot happen and depthFailOp doesn't matter.
> >
> > Does that make sense? It's not so much about figuring out which of the
> > stencil ops get taken as it is about figuring out which ones don't matter
> > because the corresponding depth and stencil test results cannot happen.
> > Then, you take the ones that do matter and look at the stencil ops. If
> any
> > of the stencil ops that *can* happen aren't KEEP, then we write stencil.
> >
> > --Jason
> >
> >
> > > > face->depthCompareOp == VK_COMPARE_OP_NEVER)
> > > > face->passOp = VK_STENCIL_OP_KEEP;
> > > >
> > > > if (face->compareOp == VK_COMPARE_OP_NEVER ||
> > > > face->depthCompareOp == VK_COMPARE_OP_ALWAYS)
> > > > face->depthFailOp = VK_STENCIL_OP_KEEP;
> > > >
> > > > return face->failOp != VK_STENCIL_OP_KEEP ||
> > > > face->depthFailOp != VK_STENCIL_OP_KEEP ||
> > > > face->passOp != VK_STENCIL_OP_KEEP;
> > >
> > > Why does this work?
> > >
> > > > }
> > > >
> > > > I thought about writing it that way at one point but I decided
> sanitizing
> > > > the stencil ops wasn't needed. I can switch if you'd rather.
> > > >
> > >
> > > I sent another function to the list before I saw this, which I think is
> > > more straight-forward. What do you think?
> > >
>
> It looks like you missed this question. The second function I sent isn't
> 100% correct, but I think the general structure of the code and comments
> is easier to grasp. I do find your explanation helpful to understanding
> how your function works. If you disagree with using my proposed function
> as a starting point, could you massage your explanation into code
> comments?
>
Yeah, I would probably say that your function is the wrong mental model. I
can definitely add more code comments and send another version.
> -Nanley
>
> > > -Nanley
> > >
> > > > >-Nanley
> > > > >
> > > > > >
> > > > > > The possible input combinations that affect writing to stencil
> can be
> > > > > > divided up into 10 sets.
> > > > > >
> > > > > > s = stencil compare op
> > > > > > d = depth compare op
> > > > > > df = depth fail op
> > > > > > sf = stencil fail op
> > > > > > sp = stencil pass op
> > > > > >
> > > > > > s.Always | !s.Always
> > > > > > d.Never | !d.Never | s.Never |
> > > > > > | d.Always | | |
> > > > > > !keep | | | |
> > > > > > | | | |
> > > > > > ------------|----------|------
> > > |--------------|--------------
> > > > > > | | | |
> > > > > > keep df.Keep | sp.Keep | | sf.Keep |
> > > > > > | | | |
> > > > > > | | | |
> > > > > >
> > > > > > We know that stencil won't be written if the function inputs
> land us
> > > in
> > > > > > 3 of these sets (denoted by the *.Keep's above). I think this
> > > function
> > > > > > would be easier to understand if it determined if we fell in one
> of
> > > the
> > > > > > 3 instead of the 7. How about something like this:
> > > > > >
> > > > > > static bool
> > > > > > wont_write_stencil_face(const VkStencilOpState *face,
> > > > > > VkCompareOp depthCompareOp)
> > > > > > {
> > > > > > if (face->compareOp == VK_COMPARE_OP_NEVER &&
> > > > > > face->failOp == VK_STENCIL_OP_KEEP)
> > > > > > return true;
> > > > > >
> > > > > > if (face->compareOp == VK_COMPARE_OP_ALWAYS) {
> > > > > > if (depthCompareOp == VK_COMPARE_OP_NEVER &&
> > > > > > face->depthFailOp == VK_STENCIL_OP_KEEP)
> > > > > > return true;
> > > > > > if (depthCompareOp == VK_COMPARE_OP_ALWAYS &&
> > > > > > face->passOp == VK_STENCIL_OP_KEEP)
> > > > > > return true;
> > > > > > }
> > > > > > return false;
> > > > > > }
> > > > > >
> > > > > > -Nanley
> > > > > >
> > > > > > > + /* If compareOp is ALWAYS then the stencil test will never
> fail
> > > > > and we can
> > > > > > > + * ignore failOp. If it's not ALWAYS and failOp is not
> KEEP,
> > > we
> > > > > may write
> > > > > > > + * stencil.
> > > > > > > + */
> > > > > > > + if (face->compareOp != VK_COMPARE_OP_ALWAYS &&
> > > > > > > + face->failOp != VK_STENCIL_OP_KEEP)
> > > > > > > + return true;
> > > > > > > +
> > > > > > > +
> > > > > > > + /* If the compareOp is NEVER then the stencil test will
> never
> > > pass
> > > > > and the
> > > > > > > + * passOp and depthFailOp don't matter. If compareOp isn't
> > > NEVER,
> > > > > then we
> > > > > > > + * need to take them into account.
> > > > > > > + */
> > > > > > > + if (face->compareOp != VK_COMPARE_OP_NEVER) {
> > > > > > > + /* If depthOp is NEVER then passOp doesn't matter. */
> > > > > > > + if (depthCompareOp != VK_COMPARE_OP_NEVER &&
> > > > > > > + face->passOp != VK_STENCIL_OP_KEEP)
> > > > > > > + return true;
> > > > > > > +
> > > > > > > + /* If depthOp is ALWAYS then depthFailOp doesn't
> matter. */
> > > > > > > + if (depthCompareOp != VK_COMPARE_OP_ALWAYS &&
> > > > > > > + face->depthFailOp != VK_STENCIL_OP_KEEP)
> > > > > > > + return true;
> > > > > > > + }
> > > > > > > +
> > > > > > > + return false;
> > > > > > > +}
> > > > > > > +
> > > > > > > +/* Intel hardware is fairly sensitive to whether or not
> > > depth/stencil
> > > > > writes
> > > > > > > + * are enabled. In the presence of discards, it's fairly
> easy to
> > > get
> > > > > into the
> > > > > > > + * non-promoted case which means a fairly big performance hit.
> > > From
> > > > > the Iron
> > > > > > > + * Lake PRM, Vol 2, pt. 1, section 8.4.3.2, "Early Depth Test
> > > Cases":
> > > > > > > + *
> > > > > > > + * "Non-promoted depth (N) is active whenever the depth
> test
> > > can
> > > > > be done
> > > > > > > + * early but it cannot determine whether or not to write
> source
> > > > > depth to
> > > > > > > + * the depth buffer, therefore the depth write must be
> > > performed
> > > > > post pixel
> > > > > > > + * shader. This includes cases where the pixel shader can
> kill
> > > > > pixels,
> > > > > > > + * including via sampler chroma key, as well as cases
> where the
> > > > > alpha test
> > > > > > > + * function is enabled, which kills pixels based on a
> > > programmable
> > > > > alpha
> > > > > > > + * test. In this case, even if the depth test fails, the
> pixel
> > > > > cannot be
> > > > > > > + * killed if a stencil write is indicated. Whether or not
> the
> > > > > stencil write
> > > > > > > + * happens depends on whether or not the pixel is killed
> > > later. In
> > > > > these
> > > > > > > + * cases if stencil test fails and stencil writes are off,
> the
> > > > > pixels can
> > > > > > > + * also be killed early. If stencil writes are enabled, the
> > > pixels
> > > > > must be
> > > > > > > + * treated as Computed depth (described above)."
> > > > > > > + *
> > > > > > > + * The same thing as mentioned in the stencil case can happen
> in
> > > the
> > > > > depth
> > > > > > > + * case as well if it thinks it writes depth but, thanks to
> the
> > > depth
> > > > > test
> > > > > > > + * being GL_EQUAL, the write doesn't actually matter. A
> little
> > > extra
> > > > > work
> > > > > > > + * up-front to try and disable depth and stencil writes can
> make
> > > a big
> > > > > > > + * difference.
> > > > > > > + *
> > > > > > > + * Unfortunately, the way depth and stencil testing is
> specified,
> > > > > there are
> > > > > > > + * many case where, regardless of depth/stencil writes being
> > > enabled,
> > > > > nothing
> > > > > > > + * actually gets written due to some other bit of state being
> set.
> > > > > This
> > > > > > > + * function attempts to "sanitize" the depth stencil state and
> > > > > disable writes
> > > > > > > + * and sometimes even testing whenever possible.
> > > > > > > + */
> > > > > > > +static void
> > > > > > > +sanitize_ds_state(VkPipelineDepthStencilStateCreateInfo
> *state,
> > > > > > > + bool *stencilWriteEnable,
> > > > > > > + VkImageAspectFlags ds_aspects)
> > > > > > > +{
> > > > > > > + *stencilWriteEnable = state->stencilTestEnable;
> > > > > > > +
> > > > > > > + /* If the depth test is disabled, we won't be writing
> > > anything. */
> > > > > > > + if (!state->depthTestEnable)
> > > > > > > + state->depthWriteEnable = false;
> > > > > > > +
> > > > > > > + /* The Vulkan spec requires that if either depth or
> stencil is
> > > not
> > > > > present,
> > > > > > > + * the pipeline is to act as if the test silently passes.
> > > > > > > + */
> > > > > > > + if (!(ds_aspects & VK_IMAGE_ASPECT_DEPTH_BIT)) {
> > > > > > > + state->depthWriteEnable = false;
> > > > > > > + state->depthCompareOp = VK_COMPARE_OP_ALWAYS;
> > > > > > > + }
> > > > > > > +
> > > > > > > + if (!(ds_aspects & VK_IMAGE_ASPECT_STENCIL_BIT)) {
> > > > > > > + *stencilWriteEnable = false;
> > > > > > > + state->front.compareOp = VK_COMPARE_OP_ALWAYS;
> > > > > > > + state->back.compareOp = VK_COMPARE_OP_ALWAYS;
> > > > > > > + }
> > > > > > > +
> > > > > > > + /* If the stencil test is enabled and always fails, then we
> > > will
> > > > > never get
> > > > > > > + * to the depth test so we can just disable the depth test
> > > > > entirely.
> > > > > > > + */
> > > > > > > + if (state->stencilTestEnable &&
> > > > > > > + state->front.compareOp == VK_COMPARE_OP_NEVER &&
> > > > > > > + state->back.compareOp == VK_COMPARE_OP_NEVER) {
> > > > > > > + state->depthTestEnable = false;
> > > > > > > + state->depthWriteEnable = false;
> > > > > > > + }
> > > > > > > +
> > > > > > > + /* If depthCompareOp is EQUAL then the value we would be
> > > writing
> > > > > to the
> > > > > > > + * depth buffer is the same as the value that's already
> there
> > > so
> > > > > there's no
> > > > > > > + * point in writing it.
> > > > > > > + */
> > > > > > > + if (state->depthCompareOp == VK_COMPARE_OP_EQUAL)
> > > > > > > + state->depthWriteEnable = false;
> > > > > > > +
> > > > > > > + /* If the stencil ops are such that we don't actually ever
> > > modify
> > > > > the
> > > > > > > + * stencil buffer, we should disable writes.
> > > > > > > + */
> > > > > > > + if (!may_write_stencil_face(&state->front,
> > > state->depthCompareOp)
> > > > > &&
> > > > > > > + !may_write_stencil_face(&state->back,
> > > state->depthCompareOp))
> > > > > > > + *stencilWriteEnable = false;
> > > > > > > +
> > > > > > > + /* If the depth test always passes and we never write out
> > > depth,
> > > > > that's the
> > > > > > > + * same as if the depth test is disabled entirely.
> > > > > > > + */
> > > > > > > + if (state->depthCompareOp == VK_COMPARE_OP_ALWAYS &&
> > > > > > > + !state->depthWriteEnable)
> > > > > > > + state->depthTestEnable = false;
> > > > > > > +
> > > > > > > + /* If the stencil test always passes and we never write out
> > > > > stencil, that's
> > > > > > > + * the same as if the stencil test is disabled entirely.
> > > > > > > + */
> > > > > > > + if (state->front.compareOp == VK_COMPARE_OP_ALWAYS &&
> > > > > > > + state->back.compareOp == VK_COMPARE_OP_ALWAYS &&
> > > > > > > + !*stencilWriteEnable)
> > > > > > > + state->stencilTestEnable = false;
> > > > > > > +}
> > > > > > > +
> > > > > > > static void
> > > > > > > emit_ds_state(struct anv_pipeline *pipeline,
> > > > > > > const VkPipelineDepthStencilStateCreateInfo
> > > > > *pCreateInfo,
> > > > > > > @@ -663,12 +790,20 @@ emit_ds_state(struct anv_pipeline
> *pipeline,
> > > > > > > return;
> > > > > > > }
> > > > > > >
> > > > > > > + VkImageAspectFlags ds_aspects = 0;
> > > > > > > + if (subpass->depth_stencil_attachment !=
> > > VK_ATTACHMENT_UNUSED) {
> > > > > > > + VkFormat depth_stencil_format =
> > > > > > > + pass->attachments[subpass->
> depth_stencil_attachment].
> > > format;
> > > > > > > + ds_aspects = vk_format_aspects(depth_stencil_format);
> > > > > > > + }
> > > > > > > +
> > > > > > > VkPipelineDepthStencilStateCreateInfo info = *pCreateInfo;
> > > > > > > + sanitize_ds_state(&info, &pipeline->writes_stencil,
> > > ds_aspects);
> > > > > > > + pipeline->writes_depth = info.depthWriteEnable;
> > > > > > > + pipeline->depth_test_enable = info.depthTestEnable;
> > > > > > >
> > > > > > > /* VkBool32 depthBoundsTestEnable; // optional
> > > (depth_bounds_test)
> > > > > */
> > > > > > >
> > > > > > > - pipeline->writes_stencil = info.stencilTestEnable;
> > > > > > > -
> > > > > > > #if GEN_GEN <= 7
> > > > > > > struct GENX(DEPTH_STENCIL_STATE) depth_stencil = {
> > > > > > > #else
> > > > > > > @@ -690,38 +825,6 @@ emit_ds_state(struct anv_pipeline
> *pipeline,
> > > > > > > .BackfaceStencilTestFunction =
> vk_to_gen_compare_op[info.
> > > > > back.compareOp],
> > > > > > > };
> > > > > > >
> > > > > > > - VkImageAspectFlags aspects = 0;
> > > > > > > - if (subpass->depth_stencil_attachment !=
> > > VK_ATTACHMENT_UNUSED) {
> > > > > > > - VkFormat depth_stencil_format =
> > > > > > > - pass->attachments[subpass->
> depth_stencil_attachment].
> > > format;
> > > > > > > - aspects = vk_format_aspects(depth_stencil_format);
> > > > > > > - }
> > > > > > > -
> > > > > > > - /* The Vulkan spec requires that if either depth or
> stencil is
> > > not
> > > > > present,
> > > > > > > - * the pipeline is to act as if the test silently passes.
> > > > > > > - */
> > > > > > > - if (!(aspects & VK_IMAGE_ASPECT_DEPTH_BIT)) {
> > > > > > > - depth_stencil.DepthBufferWriteEnable = false;
> > > > > > > - depth_stencil.DepthTestFunction = PREFILTEROPALWAYS;
> > > > > > > - }
> > > > > > > -
> > > > > > > - if (!(aspects & VK_IMAGE_ASPECT_STENCIL_BIT)) {
> > > > > > > - pipeline->writes_stencil = false;
> > > > > > > - depth_stencil.StencilTestFunction = PREFILTEROPALWAYS;
> > > > > > > - depth_stencil.BackfaceStencilTestFunction =
> > > PREFILTEROPALWAYS;
> > > > > > > - }
> > > > > > > -
> > > > > > > - /* From the Broadwell PRM:
> > > > > > > - *
> > > > > > > - * "If Depth_Test_Enable = 1 AND Depth_Test_func =
> EQUAL,
> > > the
> > > > > > > - * Depth_Write_Enable must be set to 0."
> > > > > > > - */
> > > > > > > - if (info.depthTestEnable && info.depthCompareOp ==
> > > > > VK_COMPARE_OP_EQUAL)
> > > > > > > - depth_stencil.DepthBufferWriteEnable = false;
> > > > > > > -
> > > > > > > - pipeline->writes_depth = depth_stencil.
> DepthBufferWriteEnable;
> > > > > > > - pipeline->depth_test_enable =
> depth_stencil.DepthTestEnable;
> > > > > > > -
> > > > > > > #if GEN_GEN <= 7
> > > > > > > GENX(DEPTH_STENCIL_STATE_pack)(NULL, depth_stencil_dw,
> > > > > &depth_stencil);
> > > > > > > #else
> > > > > > > --
> > > > > > > 2.5.0.400.gff86faf
> > > > > > >
> > > > > > > _______________________________________________
> > > > > > > mesa-dev mailing list
> > > > > > > mesa-dev at lists.freedesktop.org
> > > > > > > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> > > > >
> > >
>
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