Dave Airlie <airl...@gmail.com> writes: > From: Dave Airlie <airl...@redhat.com> > > This is ported from GLSL and converts > > if (cond) > discard; > > into > discard_if(cond); > > This removes a block, but also is needed by radv > to workaround a bug in the LLVM backend. > > v2: handle if (a) discard_if(b) (nha) > cleanup and drop pointless loop (Matt) > make sure there are no dependent phis (Eric) > v3: make sure only one instruction in the then block. > > Signed-off-by: Dave Airlie <airl...@redhat.com> > ---
> diff --git a/src/compiler/nir/nir_opt_conditional_discard.c
> b/src/compiler/nir/nir_opt_conditional_discard.c
> new file mode 100644
> index 0000000..6e90983
> --- /dev/null
> +++ b/src/compiler/nir/nir_opt_conditional_discard.c
> @@ -0,0 +1,125 @@
> +/*
> + * Copyright © 2016 Red Hat
> + *
> + * 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"
> +#include "nir_builder.h"
> +
> +/** @file nir_opt_conditional_discard.c
> + *
> + * Handles optimization of lowering if (cond) discard to discard_if(cond).
> + */
Maybe put some quotes around "if (cond) discard" to clarify what
statement is being lowered.
> +static bool
> +nir_opt_conditional_discard_block(nir_block *block, void *mem_ctx)
> +{
> + nir_builder bld;
> +
> + if (nir_cf_node_is_first(&block->cf_node))
> + return false;
> +
> + nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node);
> + if (prev_node->type != nir_cf_node_if)
> + return false;
> +
> + nir_if *if_stmt = nir_cf_node_as_if(prev_node);
> + nir_block *then_block = nir_if_first_then_block(if_stmt);
> + nir_block *else_block = nir_if_first_else_block(if_stmt);
> +
> + /* check there is only one else block and it is empty */
> + if (nir_if_last_else_block(if_stmt) != else_block)
> + return false;
> + if (!exec_list_is_empty(&else_block->instr_list))
> + return false;
> +
> + /* check there is only one then block and it has only one instruction in
> it */
> + if (nir_if_last_then_block(if_stmt) != then_block)
> + return false;
> + if (exec_list_is_empty(&then_block->instr_list))
> + return false;
> + if (exec_list_length(&then_block->instr_list) > 1)
> + return false;
> + /*
> + * make sure no subsequent phi nodes point at this if.
> + */
> + nir_block *after =
> nir_cf_node_as_block(nir_cf_node_next(&if_stmt->cf_node));
> + nir_foreach_instr_safe(instr, after) {
> + if (instr->type != nir_instr_type_phi)
> + break;
> + nir_phi_instr *phi = nir_instr_as_phi(instr);
> +
> + nir_foreach_phi_src(phi_src, phi) {
> + if (phi_src->pred == then_block ||
> + phi_src->pred == else_block)
> + return false;
> + }
> + }
> +
> + /* Get the first instruction in the then block and confirm it is
> + * a discard or a discard_if
> + */
> + nir_instr *instr = nir_block_first_instr(then_block);
> + if (instr->type != nir_instr_type_intrinsic)
> + return false;
> +
> + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
> + if (intrin->intrinsic != nir_intrinsic_discard &&
> + intrin->intrinsic != nir_intrinsic_discard_if)
> + return false;
> +
> + nir_src cond;
> +
> + nir_builder_init(&bld, mem_ctx);
Missing bld.cursor initialization, so the adding-to-a-discard_if case
should crash. With that fixed, this will be:
Reviewed-by: Eric Anholt <e...@anholt.net>
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