diff options
| -rw-r--r-- | src/mesa/drivers/dri/i965/brw_vec4.cpp | 49 |
1 files changed, 27 insertions, 22 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp index df589b87c79..655299472ff 100644 --- a/src/mesa/drivers/dri/i965/brw_vec4.cpp +++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp @@ -840,6 +840,32 @@ vec4_visitor::move_push_constants_to_pull_constants() pack_uniform_registers(); } +/* Conditions for which we want to avoid setting the dependency control bits */ +static bool +is_dep_ctrl_unsafe(const vec4_instruction *inst) +{ + /* + * mlen: + * In the presence of send messages, totally interrupt dependency + * control. They're long enough that the chance of dependency + * control around them just doesn't matter. + * + * predicate: + * From the Ivy Bridge PRM, volume 4 part 3.7, page 80: + * When a sequence of NoDDChk and NoDDClr are used, the last instruction that + * completes the scoreboard clear must have a non-zero execution mask. This + * means, if any kind of predication can change the execution mask or channel + * enable of the last instruction, the optimization must be avoided. This is + * to avoid instructions being shot down the pipeline when no writes are + * required. + * + * math: + * Dependency control does not work well over math instructions. + * NB: Discovered empirically + */ + return (inst->mlen || inst->predicate || inst->is_math()); +} + /** * Sets the dependency control fields on instructions after register * allocation and before the generator is run. @@ -885,28 +911,7 @@ vec4_visitor::opt_set_dependency_control() assert(inst->src[i].file != MRF); } - /* In the presence of send messages, totally interrupt dependency - * control. They're long enough that the chance of dependency - * control around them just doesn't matter. - */ - if (inst->mlen) { - memset(last_grf_write, 0, sizeof(last_grf_write)); - memset(last_mrf_write, 0, sizeof(last_mrf_write)); - continue; - } - - /* It looks like setting dependency control on a predicated - * instruction hangs the GPU. - */ - if (inst->predicate) { - memset(last_grf_write, 0, sizeof(last_grf_write)); - memset(last_mrf_write, 0, sizeof(last_mrf_write)); - continue; - } - - /* Dependency control does not work well over math instructions. - */ - if (inst->is_math()) { + if (is_dep_ctrl_unsafe(inst)) { memset(last_grf_write, 0, sizeof(last_grf_write)); memset(last_mrf_write, 0, sizeof(last_mrf_write)); continue; |