anv: Move push constant allocation to the command buffer

Instead of blasting it out as part of the pipeline, we put it in the
command buffer and only blast it out when it's really needed.  Since the
PUSH_CONSTANT_ALLOC commands aren't pipelined, they immediately cause a
stall which we would like to avoid.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

1 files changed, 69 insertions, 9 deletions

diff --git a/src/intel/vulkan/genX_cmd_buffer.c b/src/intel/vulkan/genX_cmd_buffer.c
index ee47c29..f5e3530 100644
--- a/src/intel/vulkan/genX_cmd_buffer.c
+++ b/src/intel/vulkan/genX_cmd_buffer.c
@@ -274,6 +274,72 @@ void genX(CmdPipelineBarrier)(
    }
 }
 
+static void
+cmd_buffer_alloc_push_constants(struct anv_cmd_buffer *cmd_buffer)
+{
+   VkShaderStageFlags stages = cmd_buffer->state.pipeline->active_stages;
+
+   /* In order to avoid thrash, we assume that vertex and fragment stages
+    * always exist.  In the rare case where one is missing *and* the other
+    * uses push concstants, this may be suboptimal.  However, avoiding stalls
+    * seems more important.
+    */
+   stages |= VK_SHADER_STAGE_FRAGMENT_BIT | VK_SHADER_STAGE_VERTEX_BIT;
+
+   if (stages == cmd_buffer->state.push_constant_stages)
+      return;
+
+#if GEN_GEN >= 8
+   const unsigned push_constant_kb = 32;
+#elif GEN_IS_HASWELL
+   const unsigned push_constant_kb = cmd_buffer->device->info.gt == 3 ? 32 : 16;
+#else
+   const unsigned push_constant_kb = 16;
+#endif
+
+   const unsigned num_stages =
+      _mesa_bitcount(stages & VK_SHADER_STAGE_ALL_GRAPHICS);
+   unsigned size_per_stage = push_constant_kb / num_stages;
+
+   /* Broadwell+ and Haswell gt3 require that the push constant sizes be in
+    * units of 2KB.  Incidentally, these are the same platforms that have
+    * 32KB worth of push constant space.
+    */
+   if (push_constant_kb == 32)
+      size_per_stage &= ~1u;
+
+   uint32_t kb_used = 0;
+   for (int i = MESA_SHADER_VERTEX; i < MESA_SHADER_FRAGMENT; i++) {
+      unsigned push_size = (stages & (1 << i)) ? size_per_stage : 0;
+      anv_batch_emit(&cmd_buffer->batch,
+                     GENX(3DSTATE_PUSH_CONSTANT_ALLOC_VS), alloc) {
+         alloc._3DCommandSubOpcode  = 18 + i;
+         alloc.ConstantBufferOffset = (push_size > 0) ? kb_used : 0;
+         alloc.ConstantBufferSize   = push_size;
+      }
+      kb_used += push_size;
+   }
+
+   anv_batch_emit(&cmd_buffer->batch,
+                  GENX(3DSTATE_PUSH_CONSTANT_ALLOC_PS), alloc) {
+      alloc.ConstantBufferOffset = kb_used;
+      alloc.ConstantBufferSize = push_constant_kb - kb_used;
+   }
+
+   cmd_buffer->state.push_constant_stages = stages;
+
+   /* From the BDW PRM for 3DSTATE_PUSH_CONSTANT_ALLOC_VS:
+    *
+    *    "The 3DSTATE_CONSTANT_VS must be reprogrammed prior to
+    *    the next 3DPRIMITIVE command after programming the
+    *    3DSTATE_PUSH_CONSTANT_ALLOC_VS"
+    *
+    * Since 3DSTATE_PUSH_CONSTANT_ALLOC_VS is programmed as part of
+    * pipeline setup, we need to dirty push constants.
+    */
+   cmd_buffer->state.push_constants_dirty |= VK_SHADER_STAGE_ALL_GRAPHICS;
+}
+
 static uint32_t
 cmd_buffer_flush_push_constants(struct anv_cmd_buffer *cmd_buffer)
 {
@@ -384,16 +450,10 @@ genX(cmd_buffer_flush_state)(struct anv_cmd_buffer *cmd_buffer)
 
       anv_batch_emit_batch(&cmd_buffer->batch, &pipeline->batch);
 
-      /* From the BDW PRM for 3DSTATE_PUSH_CONSTANT_ALLOC_VS:
-       *
-       *    "The 3DSTATE_CONSTANT_VS must be reprogrammed prior to
-       *    the next 3DPRIMITIVE command after programming the
-       *    3DSTATE_PUSH_CONSTANT_ALLOC_VS"
-       *
-       * Since 3DSTATE_PUSH_CONSTANT_ALLOC_VS is programmed as part of
-       * pipeline setup, we need to dirty push constants.
+      /* If the pipeline changed, we may need to re-allocate push constant
+       * space in the URB.
        */
-      cmd_buffer->state.push_constants_dirty |= VK_SHADER_STAGE_ALL_GRAPHICS;
+      cmd_buffer_alloc_push_constants(cmd_buffer);
    }
 
 #if GEN_GEN <= 7