From: Francisco Jerez Date: Fri, 24 Jan 2020 06:01:00 +0000 (-0800) Subject: intel/fs/cse: Make HALT instruction act as CSE barrier. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=c9e33e5cbf6b8b953932f283e1f0abcb6c77eb1f;p=mesa.git intel/fs/cse: Make HALT instruction act as CSE barrier. Found by inspection. This seems particularly likely to cause problems with instructions dependent on the current execution mask like SHADER_OPCODE_FIND_LIVE_CHANNEL or the FS_OPCODE_LOAD_LIVE_CHANNELS instruction I'm about to introduce, but one could imagine it leading to data corruption if CSE ever managed to combine two instructions before and after the FS_OPCODE_PLACEHOLDER_HALT, since the one before may not be executed for some channels. Reviewed-by: Caio Marcelo de Oliveira Filho Cc: 20.0 --- diff --git a/src/intel/compiler/brw_fs_cse.cpp b/src/intel/compiler/brw_fs_cse.cpp index b7c32f3907f..4751e11bcfe 100644 --- a/src/intel/compiler/brw_fs_cse.cpp +++ b/src/intel/compiler/brw_fs_cse.cpp @@ -317,6 +317,16 @@ fs_visitor::opt_cse_local(bblock_t *block, int &ip) } } + /* Discard jumps aren't represented in the CFG unfortunately, so we need + * to make sure that they behave as a CSE barrier, since we lack global + * dataflow information. This is particularly likely to cause problems + * with instructions dependent on the current execution mask like + * SHADER_OPCODE_FIND_LIVE_CHANNEL. + */ + if (inst->opcode == FS_OPCODE_DISCARD_JUMP || + inst->opcode == FS_OPCODE_PLACEHOLDER_HALT) + aeb.make_empty(); + foreach_in_list_safe(aeb_entry, entry, &aeb) { /* Kill all AEB entries that write a different value to or read from * the flag register if we just wrote it.