i965/fs: Set exec_all on unspills.

This makes sure that unspills restore the exact contents of the
variable in scratch space into the GRF without applying channel
masking, which is incorrect under control flow for things like message
headers or vectors of heterogeneous types that don't properly respect
channel boundaries.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

diff --git a/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp b/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
index 099df8b..bc847bf 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_reg_allocate.cpp
@@ -944,8 +944,16 @@ fs_visitor::spill_reg(int spill_reg)
 
             const unsigned width =
                dispatch_width == 16 && regs_read % 2 == 0 ? 16 : 8;
-            emit_unspill(ibld.group(width, 0), unspill_dst,
-                         subset_spill_offset, regs_read);
+
+            /* Set exec_all() on unspill messages under the (rather
+             * pessimistic) assumption that there is no one-to-one
+             * correspondence between channels of the spilled variable in
+             * scratch space and the scratch read message, which operates on
+             * 32 bit channels.  It shouldn't hurt in any case because the
+             * unspill destination is a block-local temporary.
+             */
+            emit_unspill(ibld.exec_all().group(width, 0),
+                         unspill_dst, subset_spill_offset, regs_read);
         }
       }