On 04/16/2014 11:07 AM, Matt Turner wrote:
> We were starting at the beginning of the instruction list, rather than
> with the MOV instruction itself. This allows us to coalesce after
> control flow.
>
> Excluding the shaders from an unreleased title, the shader-db results:
>
> total instructions in shared programs: 1603791 -> 1594215 (-0.60%)
> instructions in affected programs: 678772 -> 669196 (-1.41%)
> GAINED: 5
> LOST: 0
> ---
> .../drivers/dri/i965/brw_fs_register_coalesce.cpp | 22
> +++++++++-------------
> 1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
> b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
> index 5836fb7..58f6ca7 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
> @@ -73,7 +73,7 @@ is_coalesce_candidate(const fs_inst *inst, const int
> *virtual_grf_sizes)
>
> static bool
> can_coalesce_vars(brw::fs_live_variables *live_intervals,
> - const exec_list *instructions, const fs_inst *inst,
> + const exec_list *instructions, const fs_inst *inst, int ip,
> int var_to, int var_from)
> {
> if (!live_intervals->vars_interfere(var_from, var_to))
> @@ -92,21 +92,15 @@ can_coalesce_vars(brw::fs_live_variables *live_intervals,
> if (live_intervals->end[var_to] > live_intervals->end[var_from])
> return false;
>
> - int scan_ip = -1;
> -
> - foreach_list(n, instructions) {
> - fs_inst *scan_inst = (fs_inst *)n;
> - scan_ip++;
> + assert(ip >= live_intervals->start[var_to]);
>
> + fs_inst *scan_inst;
> + for (scan_inst = (fs_inst *)inst->next;
> + scan_inst->next != NULL && ip <= live_intervals->end[var_to];
This doesn't seem quite right to me. The last instruction in the list
will have scan_inst->next == the tail sentinel (so, ->next->next ==
NULL). I think you want:
!scan_inst->is_tail_sentinel() && ip <= live_intervals->end[var_to];
With that changed (or my logic rebuffed), this is:
Reviewed-by: Kenneth Graunke <kenn...@whitecape.org>
> + scan_inst = (fs_inst *)scan_inst->next, ip++) {
> if (scan_inst->is_control_flow())
> return false;
>
> - if (scan_ip <= live_intervals->start[var_to])
> - continue;
> -
> - if (scan_ip > live_intervals->end[var_to])
> - break;
> -
> if (scan_inst->dst.equals(inst->dst) ||
> scan_inst->dst.equals(inst->src[0]))
> return false;
> @@ -129,9 +123,11 @@ fs_visitor::register_coalesce()
> fs_inst *mov[MAX_SAMPLER_MESSAGE_SIZE];
> int var_to[MAX_SAMPLER_MESSAGE_SIZE];
> int var_from[MAX_SAMPLER_MESSAGE_SIZE];
> + int ip = -1;
>
> foreach_list(node, &this->instructions) {
> fs_inst *inst = (fs_inst *)node;
> + ip++;
>
> if (!is_coalesce_candidate(inst, virtual_grf_sizes))
> continue;
> @@ -170,7 +166,7 @@ fs_visitor::register_coalesce()
> var_to[i] = live_intervals->var_from_vgrf[reg_to] +
> reg_to_offset[i];
> var_from[i] = live_intervals->var_from_vgrf[reg_from] + i;
>
> - if (!can_coalesce_vars(live_intervals, &instructions, inst,
> + if (!can_coalesce_vars(live_intervals, &instructions, inst, ip,
> var_to[i], var_from[i])) {
> can_coalesce = false;
> reg_from = -1;
>
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