[Mesa-dev] [PATCH] i965/gen6: Align interleaved URB writes for overflow outputs as well.

[Eric Anholt]

Fixes glsl-max-varyings.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=35614
---
 src/mesa/drivers/dri/i965/brw_vs_emit.c |   35 +++++++++++++++++++++++-------
 1 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vs_emit.c b/src/mesa/drivers/dri/i965/brw_vs_emit.c
index dd4e1e6..a28cdc0 100644
--- a/src/mesa/drivers/dri/i965/brw_vs_emit.c
+++ b/src/mesa/drivers/dri/i965/brw_vs_emit.c
@@ -1553,6 +1553,26 @@ static void emit_swz( struct brw_vs_compile *c,
    }
 }
 
+static int
+align_interleaved_urb_mlen(struct brw_context *brw, int mlen)
+{
+   struct intel_context *intel = &brw->intel;
+
+   if (intel->gen >= 6) {
+      /* URB data written (does not include the message header reg) must
+       * be a multiple of 256 bits, or 2 VS registers.  See vol5c.5,
+       * section 5.4.3.2.2: URB_INTERLEAVED.
+       *
+       * URB entries are allocated on a multiple of 1024 bits, so an
+       * extra 128 bits written here to make the end align to 256 is
+       * no problem.
+       */
+      if ((mlen % 2) != 1)
+	 mlen++;
+   }
+
+   return mlen;
+}
 
 /**
  * Post-vertex-program processing.  Send the results to the URB.
@@ -1734,12 +1754,11 @@ static void emit_vertex_write( struct brw_vs_compile *c)
 
    eot = (c->first_overflow_output == 0);
 
-   msg_len = c->nr_outputs + 2 + len_vertex_header; 
-   if (intel->gen >= 6) {
-	   /* interleaved urb write message length for gen6 should be multiple of 2 */
-	   if ((msg_len % 2) != 0)
-		msg_len++;
-   }
+   /* Message header, plus VUE header, plus the (first set of) outputs. */
+   msg_len = 1 + len_vertex_header + c->nr_outputs;
+   msg_len = align_interleaved_urb_mlen(brw, msg_len);
+   /* Any outputs beyond BRW_MAX_MRF should be past first_overflow_output */
+   msg_len = MIN2(msg_len, (BRW_MAX_MRF - 1)),
 
    brw_urb_WRITE(p, 
 		 brw_null_reg(), /* dest */
@@ -1747,7 +1766,7 @@ static void emit_vertex_write( struct brw_vs_compile *c)
 		 c->r0,		/* src */
 		 0,		/* allocate */
 		 1,		/* used */
-		 MIN2(msg_len - 1, (BRW_MAX_MRF - 1)), /* msg len */
+		 msg_len,
 		 0,		/* response len */
 		 eot, 		/* eot */
 		 eot, 		/* writes complete */
@@ -1774,7 +1793,7 @@ static void emit_vertex_write( struct brw_vs_compile *c)
                     c->r0,          /* src */
                     0,              /* allocate */
                     1,              /* used */
-                    mrf,            /* msg len */
+                    align_interleaved_urb_mlen(brw, mrf),
                     0,              /* response len */
                     1,              /* eot */
                     1,              /* writes complete */
-- 
1.7.4.4