intel/brw: Enable constant propagation for a couple more logical sends

This prevents some regressions later in the MR. Once load_const
operations are marked as is_scalar, they will cesase to get the
automatic constant propagation that occurs in try_rebuild_source.

No shader-db or fossil-db changes on any Intel platform.

v2: Slightly relax source restrictions on
SHADER_OPCODE_UNALIGNED_OWORD_BLOCK_READ_LOGICAL. Add a comment
explaining the restriction.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30251>

src/intel/compiler/brw_fs_copy_propagation.cpp

@@ -1216,6 +1216,7 @@ try_constant_propagate_value(brw_reg val, brw_reg_type dst_type,
    case SHADER_OPCODE_BYTE_SCATTERED_WRITE_LOGICAL:
    case SHADER_OPCODE_BYTE_SCATTERED_READ_LOGICAL:
    case FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD:
+   case FS_OPCODE_VARYING_PULL_CONSTANT_LOAD_LOGICAL:
    case SHADER_OPCODE_BROADCAST:
    case BRW_OPCODE_MAD:
    case BRW_OPCODE_LRP:
@@ -1225,6 +1226,17 @@ try_constant_propagate_value(brw_reg val, brw_reg_type dst_type,
       progress = true;
       break;
 
+   case SHADER_OPCODE_UNALIGNED_OWORD_BLOCK_READ_LOGICAL:
+      /* The address of the send message cannot be immediate (see the
+       * assertions in brw_set_src0 in brw_eu_emit.c). There is no mechanism
+       * to legalize it later, so do not generate the invalid thing here.
+       */
+      if (arg != SURFACE_LOGICAL_SRC_ADDRESS) {
+         inst->src[arg] = val;
+         progress = true;
+      }
+      break;
+
    default:
       break;
    }