i965/fs: Don't use backend_visitor::instructions after creating the CFG.

This is a fix for a regression introduced in commit a9f8296d ("i965/fs:
Preserve the CFG in a few more places.").

The errata this code works around is described in a comment before the function:

   "[DevBW, DevCL] Errata: A destination register from a send can not be
    used as a destination register until after it has been sourced by an
    instruction with a different destination register.

The framebuffer write's sources must be in message registers, which SEND
instructions cannot have as a destination. There's no way for this
errata to affect anything at the end of the program. Just remove the
code.

Cc: 10.4, 10.5 <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=84613
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 1a09ea31569e1e3ce45c6a526b81a99c5a7e90fa..533feb4c7a6ce8ea14ace793f0b23e96bf94ad76 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -3037,16 +3037,6 @@ fs_visitor::insert_gen4_post_send_dependency_workarounds(bblock_t *block, fs_ins
       if (i == write_len)
          return;
    }
-
-   /* If we hit the end of the program, resolve all remaining dependencies out
-    * of paranoia.
-    */
-   fs_inst *last_inst = (fs_inst *)this->instructions.get_tail();
-   assert(last_inst->eot);
-   for (int i = 0; i < write_len; i++) {
-      if (needs_dep[i])
-         last_inst->insert_before(block, DEP_RESOLVE_MOV(first_write_grf + i));
-   }
 }
 
 void