On 01/08/2014 12:43 PM, Matt Turner wrote:
> total instructions in shared programs: 1500212 -> 1500153 (-0.00%)
> instructions in affected programs: 17777 -> 17718 (-0.33%)
> ---
> src/mesa/drivers/dri/i965/brw_dead_control_flow.cpp | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_dead_control_flow.cpp
> b/src/mesa/drivers/dri/i965/brw_dead_control_flow.cpp
> index 63a3e5b..82e83b8 100644
> --- a/src/mesa/drivers/dri/i965/brw_dead_control_flow.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_dead_control_flow.cpp
> @@ -33,6 +33,7 @@
> *
> * - if/endif
> * - if/else/endif
> + * - .../else/endif
Presumably the point of this is to change:
IF, foo, bar, ELSE, ENDIF ===> IF, foo, bar, ENDIF
...but if I can read, that's not what this does at all...
> */
> bool
> dead_control_flow_eliminate(backend_visitor *v)
> @@ -59,16 +60,17 @@ dead_control_flow_eliminate(backend_visitor *v)
> found = true;
> } else if (prev_inst->opcode == BRW_OPCODE_ELSE) {
> else_inst = prev_inst;
> + found = true;
>
> prev_inst = (backend_instruction *) prev_inst->prev;
> if (prev_inst->opcode == BRW_OPCODE_IF) {
> if_inst = prev_inst;
> - found = true;
> }
> }
>
> if (found) {
> - if_inst->remove();
> + if (if_inst)
> + if_inst->remove();
> if (else_inst)
> else_inst->remove();
> endif_inst->remove();
>
So in the above case...found = true, endif_inst != NULL, else_inst !=
NULL, but if_inst == NULL.
You delete ELSE, and you delete ENDIF. You leave IF in place...OUCH.
I think you could fix this by changing this to:
if (else_inst)
else_inst->remove();
if (if_inst) {
if_inst->remove();
endif_inst->remove();
}
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