On 04/16/2014 11:07 AM, Matt Turner wrote:
> And avoid rewriting other instructions unnecessarily. Removes a few
> self-moves we weren't able to handle because they were components of a
> large VGRF.
>
> instructions in affected programs: 830 -> 826 (-0.48%)
> ---
> src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 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 f6d9b68..8b37ed0 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
> @@ -44,6 +44,12 @@
> #include "brw_fs_live_variables.h"
>
> static bool
> +is_nop_mov(const fs_inst *inst)
> +{
> + return inst->dst.equals(inst->src[0]);
It feels weird having a function called is_nop_mov that doesn't ensure
that inst->opcode == BRW_OPCODE_MOV. I know it's unnecessary, since
this function is only called after is_coalesce_candidate(), but...it
might be nice to add that check anyway, or maybe a comment or assertion.
> +}
> +
> +static bool
> is_coalesce_candidate(const fs_inst *inst, const int *virtual_grf_sizes)
> {
> if (inst->opcode != BRW_OPCODE_MOV ||
> @@ -70,9 +76,7 @@ can_coalesce_vars(brw::fs_live_variables *live_intervals,
> const exec_list *instructions, const fs_inst *inst,
> int var_to, int var_from)
> {
> - if (live_intervals->vars_interfere(var_from, var_to) &&
> - !inst->dst.equals(inst->src[0])) {
> -
> + if (live_intervals->vars_interfere(var_from, var_to)) {
> /* We know that the live ranges of A (var_from) and B (var_to)
> * interfere because of the ->vars_interfere() call above. If the end
> * of B's live range is after the end of A's range, then we know two
> @@ -131,6 +135,12 @@ fs_visitor::register_coalesce()
> if (!is_coalesce_candidate(inst, virtual_grf_sizes))
> continue;
>
> + if (is_nop_mov(inst)) {
> + inst->opcode = BRW_OPCODE_NOP;
> + progress = true;
> + continue;
> + }
Having the can_coalesce_vars function alter the instruction stream also
seems strange. What do you think about moving the MOV->NOP code into
the caller? It would be outside the vars_interfere path, but I think
that's okay...
> +
> if (reg_from != inst->src[0].reg) {
> reg_from = inst->src[0].reg;
>
>
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