[Mesa-dev] [PATCH] i965/fs: Add pass to rename registers to break live ranges.

[Matt Turner]

On Mon, Apr 14, 2014 at 3:01 PM, Matt Turner <mattst88 at gmail.com> wrote:
> From: Kenneth Graunke <kenneth at whitecape.org>
>
> The pass breaks live ranges of virtual registers by allocating new
> registers when it sees an assignment to a virtual GRF it's already seen
> written.
>
> total instructions in shared programs: 1656292 -> 1651898 (-0.27%)
> instructions in affected programs:     466836 -> 462442 (-0.94%)
> GAINED:                                173
> LOST:                                  3
> ---
> [mattst88]: Perform renaming at control flow level 0, rather than bailing
>             at first sight of control flow.
>
>  src/mesa/drivers/dri/i965/brw_fs.cpp | 56 ++++++++++++++++++++++++++++++++++++
>  src/mesa/drivers/dri/i965/brw_fs.h   |  1 +
>  2 files changed, 57 insertions(+)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
> index dbce167..aa957cc 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> @@ -2076,6 +2076,61 @@ fs_visitor::opt_algebraic()
>  }
>
>  bool
> +fs_visitor::opt_register_renaming()
> +{
> +   bool progress = false;
> +   int depth = 0;
> +
> +   int remap[virtual_grf_count];
> +   memset(remap, -1, sizeof(int) * virtual_grf_count);
> +
> +   foreach_list(node, &this->instructions) {
> +      fs_inst *inst = (fs_inst *) node;
> +
> +      if (inst->opcode == BRW_OPCODE_IF || inst->opcode == BRW_OPCODE_DO) {
> +         depth++;
> +      } else if (inst->opcode == BRW_OPCODE_ENDIF ||
> +                 inst->opcode == BRW_OPCODE_WHILE) {
> +         depth--;
> +      }
> +
> +      /* Rewrite instruction sources. */
> +      for (int i = 0; i < 3; i++) {
> +         if (inst->src[i].file == GRF &&
> +             remap[inst->src[i].reg] != -1 &&
> +             remap[inst->src[i].reg] != inst->src[i].reg) {
> +            inst->src[i].reg = remap[inst->src[i].reg];
> +            progress = true;
> +         }
> +      }
> +
> +      int dst = inst->dst.reg;
> +
> +      if (depth == 0 &&
> +          inst->dst.file == GRF &&
> +          virtual_grf_sizes[inst->dst.reg] == 1 &&
> +          !inst->is_partial_write()) {
> +         if (remap[dst] == -1) {
> +            remap[dst] = dst;
> +         } else {
> +            remap[dst] = virtual_grf_alloc(virtual_grf_sizes[dst]);
> +            inst->dst.reg = remap[dst];
> +            progress = true;
> +         }
> +      } else if (inst->dst.file == GRF &&
> +                 remap[dst] != -1 &&
> +                 remap[dst] != dst) {
> +         inst->dst.reg = remap[dst];
> +         progress = true;
> +      }
> +   }
> +
> +   invalidate_live_intervals();
> +
> +   return progress;
> +}
> +
> +bool
>  fs_visitor::compute_to_mrf()
>  {
>     bool progress = false;
> @@ -3031,6 +3086,7 @@ fs_visitor::run()
>           progress = opt_peephole_sel() || progress;
>           progress = dead_control_flow_eliminate(this) || progress;
>           progress = opt_saturate_propagation() || progress;
> +         progress = opt_register_renaming() || progress;
>           progress = register_coalesce() || progress;
>          progress = compute_to_mrf() || progress;
>        } while (progress);
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
> index acf6a11..3f368c2 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.h
> +++ b/src/mesa/drivers/dri/i965/brw_fs.h
> @@ -371,6 +371,7 @@ public:
>     bool opt_copy_propagate_local(void *mem_ctx, bblock_t *block,
>                                   exec_list *acp);
>     void opt_drop_redundant_mov_to_flags();
> +   bool opt_split_live_ranges();

Rebase fail. This should obviously be opt_register_renaming().