i965/fs: Avoid constant propagation when the type sizes don't match.

The case where the source type of the instruction is smaller than the
immediate type could be handled by calculating the portion of the
immediate read by the instruction (assuming that the source channels
are aligned with the destination channels of the copy) and then
representing the same value as an immediate of the source type
(assuming such an immediate type exists), but the code below doesn't
do that, so just bail for the moment.

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

diff --git a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
index ceaaf5f..6aec506 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
@@ -538,6 +538,14 @@ fs_visitor::try_constant_propagate(fs_inst *inst, acp_entry *entry)
                                entry->dst, entry->regs_written))
          continue;
 
+      /* If the type sizes don't match each channel of the instruction is
+       * either extracting a portion of the constant (which could be handled
+       * with some effort but the code below doesn't) or reading multiple
+       * channels of the source at once.
+       */
+      if (type_sz(inst->src[i].type) != type_sz(entry->dst.type))
+         continue;
+
       fs_reg val = entry->src;
       val.type = inst->src[i].type;