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.landwer...@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)
+{
+ /* 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
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