On Dec 21, 2016 8:11 PM, "Timothy Arceri" <timothy.arc...@collabora.com>
wrote:
On Mon, 2016-12-19 at 20:11 -0800, Jason Ekstrand wrote:
> ---
> src/compiler/Makefile.sources | 1 +
> src/compiler/nir/nir.h | 2 +
> src/compiler/nir/nir_opt_trivial_continues.c | 141
> +++++++++++++++++++++++++++
> 3 files changed, 144 insertions(+)
> create mode 100644 src/compiler/nir/nir_opt_trivial_continues.c
>
> diff --git a/src/compiler/Makefile.sources
> b/src/compiler/Makefile.sources
> index ae3e5f0..a0abede 100644
> --- a/src/compiler/Makefile.sources
> +++ b/src/compiler/Makefile.sources
> @@ -242,6 +242,7 @@ NIR_FILES = \
> nir/nir_opt_loop_unroll.c \
> nir/nir_opt_peephole_select.c \
> nir/nir_opt_remove_phis.c \
> + nir/nir_opt_trivial_continues.c \
> nir/nir_opt_undef.c \
> nir/nir_phi_builder.c \
> nir/nir_phi_builder.h \
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index 89b0c70..a6c8956 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2563,6 +2563,8 @@ bool nir_opt_peephole_select(nir_shader
> *shader, unsigned limit);
>
> bool nir_opt_remove_phis(nir_shader *shader);
>
> +bool nir_opt_trivial_continues(nir_shader *shader);
> +
> bool nir_opt_undef(nir_shader *shader);
>
> bool nir_opt_conditional_discard(nir_shader *shader);
> diff --git a/src/compiler/nir/nir_opt_trivial_continues.c
> b/src/compiler/nir/nir_opt_trivial_continues.c
> new file mode 100644
> index 0000000..ff3205d
> --- /dev/null
> +++ b/src/compiler/nir/nir_opt_trivial_continues.c
> @@ -0,0 +1,141 @@
> +/*
> + * Copyright © 2016 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person
> obtaining a
> + * copy of this software and associated documentation files (the
> "Software"),
> + * to deal in the Software without restriction, including without
> limitation
> + * the rights to use, copy, modify, merge, publish, distribute,
> sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom
> the
> + * Software is furnished to do so, subject to the following
> conditions:
> + *
> + * The above copyright notice and this permission notice (including
> the next
> + * paragraph) shall be included in all copies or substantial
> portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
> EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
> OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> OTHER DEALINGS
> + * IN THE SOFTWARE.
> + */
> +
> +#include "nir.h"
> +
> +static bool
> +instr_is_continue(nir_instr *instr)
> +{
> + if (instr->type != nir_instr_type_jump)
> + return false;
> +
> + return nir_instr_as_jump(instr)->type == nir_jump_continue;
> +}
> +
> +static bool
> +lower_trivial_continues_block(nir_block *block, nir_loop *loop)
> +{
> + bool progress = false;
> + nir_instr *first_instr = nir_block_first_instr(block);
> + if (!first_instr || instr_is_continue(first_instr)) {
> + /* The block contains only a continue if anything */
> + nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node);
> + if (prev_node && prev_node->type == nir_cf_node_if) {
> + nir_if *prev_if = nir_cf_node_as_if(prev_node);
> + progress |= lower_trivial_continues_block(
> + nir_if_last_then_block(prev_if), loop);
> + progress |= lower_trivial_continues_block(
> + nir_if_last_else_block(prev_if), loop);
> + }
> +
> + /* The lower_phis_to_regs helper is smart enough to push phi
> sources as
> + * far up if-ladders as it possibly can. In other words, the
> recursive
> + * calls above shouldn't be adding instructions to this block
> since it
> + * follows an if statement.
> + */
> + first_instr = nir_block_first_instr(block);
> + assert(!first_instr || instr_is_continue(first_instr));
> + }
> +
> + nir_instr *last_instr = nir_block_last_instr(block);
> + if (!last_instr || !instr_is_continue(last_instr))
> + return progress;
> +
> + /* We're at the end of a block that goes straight through to the
> end of the
> + * loop and continues to the top. We can exit normally instead
> of jump.
> + */
> + nir_lower_phis_to_regs_block(nir_loop_first_block(loop));
> + nir_instr_remove(last_instr);
> + return true;
> +}
> +
> +static bool
> +lower_trivial_continues_list(struct exec_list *cf_list,
> + bool list_ends_at_loop_tail,
> + nir_loop *loop)
> +{
> + bool progress = false;
> + foreach_list_typed(nir_cf_node, cf_node, node, cf_list) {
> + bool at_loop_tail = list_ends_at_loop_tail &&
> + &cf_node->node ==
> exec_list_get_tail(cf_list);
> + switch (cf_node->type) {
> + case nir_cf_node_block:
> + break;
> +
> + case nir_cf_node_if: {
> + nir_if *nif = nir_cf_node_as_if(cf_node);
> + if (lower_trivial_continues_list(&nif->then_list,
> at_loop_tail, loop))
> + progress = true;
> + if (lower_trivial_continues_list(&nif->else_list,
> at_loop_tail, loop))
> + progress = true;
> + break;
> + }
> +
> + case nir_cf_node_loop: {
> + nir_loop *loop = nir_cf_node_as_loop(cf_node);
> + if (lower_trivial_continues_list(&loop->body, true, loop))
> + progress = true;
> + if
> (lower_trivial_continues_block(nir_loop_last_block(loop), loop))
> + progress = true;
> + break;
> + }
> +
> + case nir_cf_node_function:
> + unreachable("Invalid cf type");
> + }
> + }
> +
> + return progress;
> +}
> +
> +/**
> + * This simple pass gets rid of any "trivial" continues, i.e. those
> that are
> + * at the tail of a loop where we can just delete the continue
> instruction and
> + * control-flow will naturally and harmlessly take us back to the
> top of the
> + * loop.
> + */
> +bool
> +nir_opt_trivial_continues(nir_shader *shader)
> +{
> + bool progress = false;
> +
> + nir_foreach_function(function, shader) {
> + if (function->impl == NULL)
> + continue;
> +
> + /* First we run the simple pass to get rid of pesky continues
> */
> + if (lower_trivial_continues_list(&function->impl->body, false,
> NULL)) {
> + nir_metadata_preserve(function->impl, nir_metadata_none);
> +
> + /* If that made progress, we're no longer really in SSA
> form. Go
> + * back into SSA form and clean up.
> + */
> + nir_convert_to_ssa_impl(function->impl);
> + nir_copy_prop_impl(function->impl);
> + nir_opt_dce_impl(function->impl);
Just curious why you explicitly call these rather than just let them
get cleaned up normally? Does it cut compile times to get rid of them
straight away?
The nir_opt_if pass I wrote relies on this pass. Of this pass is run, it
also needs copy_prop and dce. This potentially allows is to drop an
iteration of the optimization loop. Another option would be to do this in
brw_nir.c:
if (OPT(nir_opt_trivial_continues)) {
OPT(nir_opt_copy_prop);
OPT(nir_opt_dce);
}
I don't have a strong preference either way.
Anyway this looks good to me and very easy to follow:
Reviewed-by: Timothy Arceri <timothy.arc...@collabora.com>
> + progress = true;
> + }
> + }
> +
> + return progress;
> +}
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