Mesa (master): iris: Refactor push constant allocation so we can reuse it

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Module: Mesa
Branch: master
Commit: f1bba22f69323eb4b7fc11abab3d14ecacafa5b4
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f1bba22f69323eb4b7fc11abab3d14ecacafa5b4

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Sat Oct  5 14:48:46 2019 -0400

iris: Refactor push constant allocation so we can reuse it

We'll need this for a workaround shortly.  While refactoring, also
improve the comment slightly.

---

 src/gallium/drivers/iris/iris_state.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/gallium/drivers/iris/iris_state.c b/src/gallium/drivers/iris/iris_state.c
index 3278a2857b7..b66eee791d1 100644
--- a/src/gallium/drivers/iris/iris_state.c
+++ b/src/gallium/drivers/iris/iris_state.c
@@ -748,6 +748,27 @@ iris_upload_slice_hashing_state(struct iris_batch *batch)
 }
 #endif
 
+static void
+iris_alloc_push_constants(struct iris_batch *batch)
+{
+   /* For now, we set a static partitioning of the push constant area,
+    * assuming that all stages could be in use.
+    *
+    * TODO: Try lazily allocating the HS/DS/GS sections as needed, and
+    *       see if that improves performance by offering more space to
+    *       the VS/FS when those aren't in use.  Also, try dynamically
+    *       enabling/disabling it like i965 does.  This would be more
+    *       stalls and may not actually help; we don't know yet.
+    */
+   for (int i = 0; i <= MESA_SHADER_FRAGMENT; i++) {
+      iris_emit_cmd(batch, GENX(3DSTATE_PUSH_CONSTANT_ALLOC_VS), alloc) {
+         alloc._3DCommandSubOpcode = 18 + i;
+         alloc.ConstantBufferOffset = 6 * i;
+         alloc.ConstantBufferSize = i == MESA_SHADER_FRAGMENT ? 8 : 6;
+      }
+   }
+}
+
 /**
  * Upload the initial GPU state for a render context.
  *
@@ -858,15 +879,7 @@ iris_init_render_context(struct iris_screen *screen,
    /* TODO: may need to set an offset for origin-UL framebuffers */
    iris_emit_cmd(batch, GENX(3DSTATE_POLY_STIPPLE_OFFSET), foo);
 
-   /* Set a static partitioning of the push constant area. */
-   /* TODO: this may be a bad idea...could starve the push ringbuffers... */
-   for (int i = 0; i <= MESA_SHADER_FRAGMENT; i++) {
-      iris_emit_cmd(batch, GENX(3DSTATE_PUSH_CONSTANT_ALLOC_VS), alloc) {
-         alloc._3DCommandSubOpcode = 18 + i;
-         alloc.ConstantBufferOffset = 6 * i;
-         alloc.ConstantBufferSize = i == MESA_SHADER_FRAGMENT ? 8 : 6;
-      }
-   }
+   iris_alloc_push_constants(batch);
 
 #if GEN_GEN == 10
    /* Gen11+ is enabled for us by the kernel. */