mirror of
https://gitlab.freedesktop.org/mesa/mesa.git
synced 2025-12-30 14:20:11 +01:00
f3290219ab
We don't need one bit per bitsize per instruction if only one actually matters in the end. First step towards moving NIR in the direction of full float_controls2 only. Also rename this from fp_fast_math, because that name implied that 0 is the no fast math mode, while the opposite was the case. Reviewed-by: Marek Olšák <marek.olsak@amd.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39026>
1560 lines
52 KiB
C
1560 lines
52 KiB
C
/*
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* Copyright © 2016 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#include "nir/nir_builder.h"
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#include "nir.h"
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#include "nir_constant_expressions.h"
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#include "nir_control_flow.h"
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#include "nir_loop_analyze.h"
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static nir_def *clone_alu_and_replace_src_defs(nir_builder *b,
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const nir_alu_instr *alu,
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nir_def **src_defs);
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/**
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* Gets the single block that jumps back to the loop header. Already assumes
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* there is exactly one such block.
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*/
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static nir_block *
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find_continue_block(nir_loop *loop)
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{
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nir_block *header_block = nir_loop_first_block(loop);
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nir_block *prev_block =
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nir_cf_node_as_block(nir_cf_node_prev(&loop->cf_node));
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assert(header_block->predecessors.entries == 2);
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set_foreach(&header_block->predecessors, pred_entry) {
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if (pred_entry->key != prev_block)
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return (nir_block *)pred_entry->key;
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}
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UNREACHABLE("Continue block not found!");
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}
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/**
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* Does a phi have one constant value from outside a loop and one from inside?
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*/
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static bool
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phi_has_constant_from_outside_and_one_from_inside_loop(nir_phi_instr *phi,
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const nir_block *entry_block,
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bool *entry_val,
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bool *continue_val)
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{
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/* We already know we have exactly one continue */
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assert(exec_list_length(&phi->srcs) == 2);
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*entry_val = false;
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*continue_val = false;
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nir_foreach_phi_src(src, phi) {
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if (!nir_src_is_const(src->src))
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return false;
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if (src->pred != entry_block) {
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*continue_val = nir_src_as_bool(src->src);
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} else {
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*entry_val = nir_src_as_bool(src->src);
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}
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}
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return true;
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}
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/**
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* This optimization detects if statements at the tops of loops where the
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* condition is a phi node of two constants and moves half of the if to above
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* the loop and the other half of the if to the end of the loop. A simple for
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* loop "for (int i = 0; i < 4; i++)", when run through the SPIR-V front-end,
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* ends up looking something like this:
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*
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* vec1 32 ssa_0 = load_const (0x00000000)
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* vec1 32 ssa_1 = load_const (0xffffffff)
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* loop {
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* block block_1:
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* vec1 32 ssa_2 = phi block_0: ssa_0, block_7: ssa_5
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* vec1 32 ssa_3 = phi block_0: ssa_0, block_7: ssa_1
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* if ssa_3 {
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* block block_2:
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* vec1 32 ssa_4 = load_const (0x00000001)
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* vec1 32 ssa_5 = iadd ssa_2, ssa_4
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* } else {
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* block block_3:
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* }
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* block block_4:
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* vec1 32 ssa_6 = load_const (0x00000004)
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* vec1 32 ssa_7 = ilt ssa_5, ssa_6
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* if ssa_7 {
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* block block_5:
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* } else {
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* block block_6:
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* break
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* }
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* block block_7:
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* }
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*
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* This turns it into something like this:
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*
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* // Stuff from block 1
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* // Stuff from block 3
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* loop {
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* block block_1:
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* vec1 32 ssa_2 = phi block_0: ssa_0, block_7: ssa_5
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* vec1 32 ssa_6 = load_const (0x00000004)
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* vec1 32 ssa_7 = ilt ssa_2, ssa_6
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* if ssa_7 {
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* block block_5:
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* } else {
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* block block_6:
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* break
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* }
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* block block_7:
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* // Stuff from block 1
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* // Stuff from block 2
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* vec1 32 ssa_4 = load_const (0x00000001)
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* vec1 32 ssa_5 = iadd ssa_2, ssa_4
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* }
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*/
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static bool
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opt_peel_loop_initial_if(nir_loop *loop)
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{
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nir_block *header_block = nir_loop_first_block(loop);
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nir_block *const prev_block =
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nir_cf_node_as_block(nir_cf_node_prev(&loop->cf_node));
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/* It would be insane if this were not true */
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assert(_mesa_set_search(&header_block->predecessors, prev_block));
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/* The loop must have exactly one continue block which could be a block
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* ending in a continue instruction or the "natural" continue from the
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* last block in the loop back to the top.
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*/
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if (header_block->predecessors.entries != 2)
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return false;
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nir_cf_node *if_node = nir_cf_node_next(&header_block->cf_node);
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if (!if_node || if_node->type != nir_cf_node_if)
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return false;
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nir_if *nif = nir_cf_node_as_if(if_node);
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nir_def *cond = nif->condition.ssa;
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if (!nir_def_is_phi(cond))
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return false;
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nir_phi_instr *cond_phi = nir_def_as_phi(cond);
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if (nir_def_block(cond) != header_block)
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return false;
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bool entry_val = false, continue_val = false;
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if (!phi_has_constant_from_outside_and_one_from_inside_loop(cond_phi,
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prev_block,
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&entry_val,
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&continue_val))
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return false;
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/* If they both execute or both don't execute, this is a job for
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* nir_dead_cf, not this pass.
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*/
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if ((entry_val && continue_val) || (!entry_val && !continue_val))
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return false;
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struct exec_list *continue_list, *entry_list;
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if (continue_val) {
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continue_list = &nif->then_list;
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entry_list = &nif->else_list;
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} else {
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continue_list = &nif->else_list;
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entry_list = &nif->then_list;
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}
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/* We want to be moving the contents of entry_list to above the loop so it
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* can't contain any break or continue instructions.
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*/
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foreach_list_typed(nir_cf_node, cf_node, node, entry_list) {
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nir_foreach_block_in_cf_node(block, cf_node) {
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if (nir_block_ends_in_jump(block))
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return false;
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}
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}
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/* We're about to re-arrange a bunch of blocks so make sure that we don't
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* have deref uses which cross block boundaries. We don't want a deref
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* accidentally ending up in a phi.
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*/
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nir_rematerialize_derefs_in_use_blocks_impl(
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nir_cf_node_get_function(&loop->cf_node));
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/* Before we do anything, convert the loop to LCSSA. We're about to
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* replace a bunch of SSA defs with registers and this will prevent any of
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* it from leaking outside the loop.
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*/
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nir_convert_loop_to_lcssa(loop);
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nir_block *after_if_block =
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nir_cf_node_as_block(nir_cf_node_next(&nif->cf_node));
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/* Get rid of phis in the header block since we will be duplicating it */
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nir_lower_phis_to_regs_block(header_block, false);
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/* Get rid of phis after the if since dominance will change */
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nir_lower_phis_to_regs_block(after_if_block, false);
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/* Get rid of SSA defs in the pieces we're about to move around */
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nir_lower_ssa_defs_to_regs_block(header_block);
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nir_foreach_block_in_cf_node(block, &nif->cf_node)
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nir_lower_ssa_defs_to_regs_block(block);
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nir_cf_list header, tmp;
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nir_cf_extract(&header, nir_before_block(header_block),
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nir_after_block(header_block));
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nir_cf_list_clone(&tmp, &header, &loop->cf_node, NULL);
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nir_cf_reinsert(&tmp, nir_before_cf_node(&loop->cf_node));
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nir_cf_extract(&tmp, nir_before_cf_list(entry_list),
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nir_after_cf_list(entry_list));
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nir_cf_reinsert(&tmp, nir_before_cf_node(&loop->cf_node));
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nir_cf_reinsert(&header,
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nir_after_block_before_jump(find_continue_block(loop)));
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bool continue_list_jumps =
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nir_block_ends_in_jump(exec_node_data(nir_block,
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exec_list_get_tail(continue_list),
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cf_node.node));
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nir_cf_extract(&tmp, nir_before_cf_list(continue_list),
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nir_after_cf_list(continue_list));
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/* Get continue block again as the previous reinsert might have removed the
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* block. Also, if both the continue list and the continue block ends in
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* jump instructions, removes the jump from the latter, as it will not be
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* executed if we insert the continue list before it. */
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nir_block *continue_block = find_continue_block(loop);
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if (continue_list_jumps) {
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nir_instr *last_instr = nir_block_last_instr(continue_block);
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if (last_instr && last_instr->type == nir_instr_type_jump)
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nir_instr_remove(last_instr);
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}
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nir_cf_reinsert(&tmp,
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nir_after_block_before_jump(continue_block));
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nir_cf_node_remove(&nif->cf_node);
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return true;
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}
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static bool
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alu_instr_is_type_conversion(const nir_alu_instr *alu)
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{
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return nir_op_infos[alu->op].num_inputs == 1 &&
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nir_op_infos[alu->op].output_type != nir_op_infos[alu->op].input_types[0];
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}
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static bool
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is_trivial_bcsel(const nir_instr *instr, bool allow_non_phi_src)
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{
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if (instr->type != nir_instr_type_alu)
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return false;
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nir_alu_instr *const bcsel = nir_instr_as_alu(instr);
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if (!nir_op_is_selection(bcsel->op))
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return false;
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for (unsigned i = 0; i < 3; i++) {
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if (!nir_alu_src_is_trivial_ssa(bcsel, i) ||
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nir_def_block(bcsel->src[i].src.ssa) != instr->block)
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return false;
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if (!nir_src_is_phi(bcsel->src[i].src)) {
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/* opt_split_alu_of_phi() is able to peel that src from the loop */
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if (i == 0 || !allow_non_phi_src)
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return false;
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allow_non_phi_src = false;
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}
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}
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nir_foreach_phi_src(src, nir_def_as_phi(bcsel->src[0].src.ssa)) {
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if (!nir_src_is_const(src->src))
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return false;
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}
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return true;
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}
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/**
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* Splits ALU instructions that have a source that is a phi node
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*
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* ALU instructions in the header block of a loop that meet the following
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* criteria can be split.
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*
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* - The loop has no continue instructions other than the "natural" continue
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* at the bottom of the loop.
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*
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* - At least one source of the instruction is a phi node from the header block.
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*
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* - Any non-phi sources of the ALU instruction come from a block that
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* dominates the block before the loop. The most common failure mode for
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* this check is sources that are generated in the loop header block.
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*
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* - The phi node selects a constant or undef from the block before the loop or
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* the only ALU user is a trivial bcsel that gets removed by peeling the ALU
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*
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* The split process splits the original ALU instruction into two, one at the
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* bottom of the loop and one at the block before the loop. The instruction
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* before the loop computes the value on the first iteration, and the
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* instruction at the bottom computes the value on the second, third, and so
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* on. A new phi node is added to the header block that selects either the
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* instruction before the loop or the one at the end, and uses of the original
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* instruction are replaced by this phi.
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*
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* The splitting transforms a loop like:
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*
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* vec1 32 ssa_8 = load_const (0x00000001)
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* vec1 32 ssa_10 = load_const (0x00000000)
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* // succs: block_1
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* loop {
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* block block_1:
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* // preds: block_0 block_4
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* vec1 32 ssa_11 = phi block_0: ssa_10, block_4: ssa_15
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* vec1 32 ssa_12 = phi block_0: ssa_1, block_4: ssa_15
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* vec1 32 ssa_13 = phi block_0: ssa_10, block_4: ssa_16
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* vec1 32 ssa_14 = iadd ssa_11, ssa_8
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* vec1 32 ssa_15 = b32csel ssa_13, ssa_14, ssa_12
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* ...
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* // succs: block_1
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* }
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*
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* into:
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*
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* vec1 32 ssa_8 = load_const (0x00000001)
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* vec1 32 ssa_10 = load_const (0x00000000)
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* vec1 32 ssa_22 = iadd ssa_10, ssa_8
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* // succs: block_1
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* loop {
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* block block_1:
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* // preds: block_0 block_4
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* vec1 32 ssa_11 = phi block_0: ssa_10, block_4: ssa_15
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* vec1 32 ssa_12 = phi block_0: ssa_1, block_4: ssa_15
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* vec1 32 ssa_13 = phi block_0: ssa_10, block_4: ssa_16
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* vec1 32 ssa_21 = phi block_0: ssa_22, block_4: ssa_20
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* vec1 32 ssa_15 = b32csel ssa_13, ssa_21, ssa_12
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* ...
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* vec1 32 ssa_20 = iadd ssa_15, ssa_8
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* // succs: block_1
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* }
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*/
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static bool
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opt_split_alu_of_phi(nir_builder *b, nir_loop *loop, nir_opt_if_options options)
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{
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bool progress = false;
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nir_block *header_block = nir_loop_first_block(loop);
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nir_block *const prev_block =
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nir_cf_node_as_block(nir_cf_node_prev(&loop->cf_node));
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/* It would be insane if this were not true */
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assert(_mesa_set_search(&header_block->predecessors, prev_block));
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/* The loop must have exactly one continue block which could be a block
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* ending in a continue instruction or the "natural" continue from the
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* last block in the loop back to the top.
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*/
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if (header_block->predecessors.entries != 2)
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return false;
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nir_block *continue_block = find_continue_block(loop);
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if (continue_block == header_block)
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return false;
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/* If the continue block is otherwise empty, leave it that way. This must match
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* opt_loop_peel_initial_break so that this optimization doesn't fight that one.
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*/
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if (!nir_block_contains_work(continue_block))
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return false;
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nir_foreach_instr_safe(instr, header_block) {
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if (instr->type != nir_instr_type_alu)
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continue;
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nir_alu_instr *const alu = nir_instr_as_alu(instr);
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/* nir_op_vec{2,3,4} and nir_op_mov are excluded because they can easily
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* lead to infinite optimization loops. Splitting comparisons can lead
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* to loop unrolling not recognizing loop termintators, and type
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* conversions also lead to regressions.
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*/
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if (nir_op_is_vec_or_mov(alu->op) ||
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nir_alu_instr_is_comparison(alu) ||
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alu_instr_is_type_conversion(alu) ||
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/* Avoid fighting with nir_lower_64bit_phis */
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(alu->def.bit_size == 64 && (options & nir_opt_if_avoid_64bit_phis)))
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continue;
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bool has_phi_src_from_prev_block = false;
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bool all_non_phi_exist_in_prev_block = true;
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bool is_prev_result_undef = true;
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bool is_prev_result_const = true;
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nir_def *prev_srcs[8]; // FINISHME: Array size?
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nir_def *continue_srcs[8]; // FINISHME: Array size?
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for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
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nir_instr *const src_instr = nir_def_instr(alu->src[i].src.ssa);
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/* If the source is a phi in the loop header block, then the
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* prev_srcs and continue_srcs will come from the different sources
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* of the phi.
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*/
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if (src_instr->type == nir_instr_type_phi &&
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src_instr->block == header_block) {
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nir_phi_instr *const phi = nir_instr_as_phi(src_instr);
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/* Only strictly need to NULL out the pointers when the assertions
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* (below) are compiled in. Debugging a NULL pointer deref in the
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|
* wild is easier than debugging a random pointer deref, so set
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* NULL unconditionally just to be safe.
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*/
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prev_srcs[i] = NULL;
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continue_srcs[i] = NULL;
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nir_foreach_phi_src(src_of_phi, phi) {
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if (src_of_phi->pred == prev_block) {
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|
if (!nir_src_is_undef(src_of_phi->src)) {
|
|
is_prev_result_undef = false;
|
|
}
|
|
|
|
if (!nir_src_is_const(src_of_phi->src)) {
|
|
is_prev_result_const = false;
|
|
}
|
|
|
|
prev_srcs[i] = src_of_phi->src.ssa;
|
|
has_phi_src_from_prev_block = true;
|
|
} else
|
|
continue_srcs[i] = src_of_phi->src.ssa;
|
|
}
|
|
|
|
assert(prev_srcs[i] != NULL);
|
|
assert(continue_srcs[i] != NULL);
|
|
} else {
|
|
/* If the source is not a phi (or a phi in a block other than the
|
|
* loop header), then the value must exist in prev_block.
|
|
*/
|
|
if (!nir_block_dominates(src_instr->block, prev_block)) {
|
|
all_non_phi_exist_in_prev_block = false;
|
|
break;
|
|
}
|
|
|
|
prev_srcs[i] = alu->src[i].src.ssa;
|
|
continue_srcs[i] = alu->src[i].src.ssa;
|
|
}
|
|
}
|
|
|
|
if (!has_phi_src_from_prev_block || !all_non_phi_exist_in_prev_block)
|
|
continue;
|
|
|
|
if (!is_prev_result_undef && !is_prev_result_const) {
|
|
/* check if the only user is a trivial bcsel */
|
|
if (!list_is_singular(&alu->def.uses))
|
|
continue;
|
|
|
|
nir_src *use = list_first_entry(&alu->def.uses, nir_src, use_link);
|
|
if (nir_src_is_if(use) || !is_trivial_bcsel(nir_src_parent_instr(use), true))
|
|
continue;
|
|
}
|
|
|
|
/* Split ALU of Phi */
|
|
b->cursor = nir_after_block(prev_block);
|
|
nir_def *prev_value = clone_alu_and_replace_src_defs(b, alu, prev_srcs);
|
|
|
|
/* Make a copy of the original ALU instruction. Replace the sources
|
|
* of the new instruction that read a phi with an undef source from
|
|
* prev_block with the non-undef source of that phi.
|
|
*
|
|
* Insert the new instruction at the end of the continue block.
|
|
*/
|
|
b->cursor = nir_after_block_before_jump(continue_block);
|
|
|
|
nir_def *const alu_copy =
|
|
clone_alu_and_replace_src_defs(b, alu, continue_srcs);
|
|
|
|
/* Make a new phi node that selects a value from prev_block and the
|
|
* result of the new instruction from continue_block.
|
|
*/
|
|
nir_phi_instr *const phi = nir_phi_instr_create(b->shader);
|
|
nir_phi_instr_add_src(phi, prev_block, prev_value);
|
|
nir_phi_instr_add_src(phi, continue_block, alu_copy);
|
|
|
|
nir_def_init(&phi->instr, &phi->def, alu_copy->num_components,
|
|
alu_copy->bit_size);
|
|
|
|
b->cursor = nir_after_phis(header_block);
|
|
nir_builder_instr_insert(b, &phi->instr);
|
|
|
|
/* Modify all readers of the original ALU instruction to read the
|
|
* result of the phi.
|
|
*/
|
|
nir_def_rewrite_uses(&alu->def,
|
|
&phi->def);
|
|
|
|
/* Since the original ALU instruction no longer has any readers, just
|
|
* remove it.
|
|
*/
|
|
nir_instr_remove_v(&alu->instr);
|
|
nir_instr_free(&alu->instr);
|
|
|
|
progress = true;
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
/**
|
|
* Simplify a bcsel whose sources are all phi nodes from the loop header block
|
|
*
|
|
* bcsel instructions in a loop that meet the following criteria can be
|
|
* converted to phi nodes:
|
|
*
|
|
* - The loop has no continue instructions other than the "natural" continue
|
|
* at the bottom of the loop.
|
|
*
|
|
* - All of the sources of the bcsel are phi nodes in the header block of the
|
|
* loop.
|
|
*
|
|
* - The phi node representing the condition of the bcsel instruction chooses
|
|
* only constant values.
|
|
*
|
|
* The contant value from the condition will select one of the other sources
|
|
* when entered from outside the loop and the remaining source when entered
|
|
* from the continue block. Since each of these sources is also a phi node in
|
|
* the header block, the value of the phi node can be "evaluated." These
|
|
* evaluated phi nodes provide the sources for a new phi node. All users of
|
|
* the bcsel result are updated to use the phi node result.
|
|
*
|
|
* The replacement transforms loops like:
|
|
*
|
|
* vec1 32 ssa_7 = undefined
|
|
* vec1 32 ssa_8 = load_const (0x00000001)
|
|
* vec1 32 ssa_9 = load_const (0x000000c8)
|
|
* vec1 32 ssa_10 = load_const (0x00000000)
|
|
* // succs: block_1
|
|
* loop {
|
|
* block block_1:
|
|
* // preds: block_0 block_4
|
|
* vec1 32 ssa_11 = phi block_0: ssa_1, block_4: ssa_14
|
|
* vec1 32 ssa_12 = phi block_0: ssa_10, block_4: ssa_15
|
|
* vec1 32 ssa_13 = phi block_0: ssa_7, block_4: ssa_25
|
|
* vec1 32 ssa_14 = b32csel ssa_12, ssa_13, ssa_11
|
|
* vec1 32 ssa_16 = ige32 ssa_14, ssa_9
|
|
* ...
|
|
* vec1 32 ssa_15 = load_const (0xffffffff)
|
|
* ...
|
|
* vec1 32 ssa_25 = iadd ssa_14, ssa_8
|
|
* // succs: block_1
|
|
* }
|
|
*
|
|
* into:
|
|
*
|
|
* vec1 32 ssa_7 = undefined
|
|
* vec1 32 ssa_8 = load_const (0x00000001)
|
|
* vec1 32 ssa_9 = load_const (0x000000c8)
|
|
* vec1 32 ssa_10 = load_const (0x00000000)
|
|
* // succs: block_1
|
|
* loop {
|
|
* block block_1:
|
|
* // preds: block_0 block_4
|
|
* vec1 32 ssa_11 = phi block_0: ssa_1, block_4: ssa_14
|
|
* vec1 32 ssa_12 = phi block_0: ssa_10, block_4: ssa_15
|
|
* vec1 32 ssa_13 = phi block_0: ssa_7, block_4: ssa_25
|
|
* vec1 32 sss_26 = phi block_0: ssa_1, block_4: ssa_25
|
|
* vec1 32 ssa_16 = ige32 ssa_26, ssa_9
|
|
* ...
|
|
* vec1 32 ssa_15 = load_const (0xffffffff)
|
|
* ...
|
|
* vec1 32 ssa_25 = iadd ssa_26, ssa_8
|
|
* // succs: block_1
|
|
* }
|
|
*
|
|
* \note
|
|
* It may be possible modify this function to not require a phi node as the
|
|
* source of the bcsel that is selected when entering from outside the loop.
|
|
* The only restriction is that the source must be geneated outside the loop
|
|
* (since it will become the source of a phi node in the header block of the
|
|
* loop).
|
|
*/
|
|
static bool
|
|
opt_simplify_bcsel_of_phi(nir_builder *b, nir_loop *loop)
|
|
{
|
|
bool progress = false;
|
|
nir_block *header_block = nir_loop_first_block(loop);
|
|
nir_block *const prev_block =
|
|
nir_cf_node_as_block(nir_cf_node_prev(&loop->cf_node));
|
|
|
|
/* It would be insane if this were not true */
|
|
assert(_mesa_set_search(&header_block->predecessors, prev_block));
|
|
|
|
/* The loop must have exactly one continue block which could be a block
|
|
* ending in a continue instruction or the "natural" continue from the
|
|
* last block in the loop back to the top.
|
|
*/
|
|
if (header_block->predecessors.entries != 2)
|
|
return false;
|
|
|
|
/* We can move any bcsel that can guaranteed to execut on every iteration
|
|
* of a loop. For now this is accomplished by only taking bcsels from the
|
|
* header_block. In the future, this could be expanced to include any
|
|
* bcsel that must come before any break.
|
|
*
|
|
* For more details, see
|
|
* https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/170#note_110305
|
|
*/
|
|
nir_foreach_instr_safe(instr, header_block) {
|
|
if (!is_trivial_bcsel(instr, false))
|
|
continue;
|
|
|
|
nir_alu_instr *const bcsel = nir_instr_as_alu(instr);
|
|
nir_phi_instr *const cond_phi =
|
|
nir_def_as_phi(bcsel->src[0].src.ssa);
|
|
|
|
bool entry_val = false, continue_val = false;
|
|
if (!phi_has_constant_from_outside_and_one_from_inside_loop(cond_phi,
|
|
prev_block,
|
|
&entry_val,
|
|
&continue_val))
|
|
continue;
|
|
|
|
/* If they both execute or both don't execute, this is a job for
|
|
* nir_dead_cf, not this pass.
|
|
*/
|
|
if ((entry_val && continue_val) || (!entry_val && !continue_val))
|
|
continue;
|
|
|
|
const unsigned entry_src = entry_val ? 1 : 2;
|
|
const unsigned continue_src = entry_val ? 2 : 1;
|
|
|
|
/* Create a new phi node that selects the value for prev_block from
|
|
* the bcsel source that is selected by entry_val and the value for
|
|
* continue_block from the other bcsel source. Both sources have
|
|
* already been verified to be phi nodes.
|
|
*/
|
|
nir_block *continue_block = find_continue_block(loop);
|
|
nir_phi_instr *const phi = nir_phi_instr_create(b->shader);
|
|
nir_phi_instr_add_src(phi, prev_block,
|
|
nir_phi_get_src_from_block(nir_def_as_phi(bcsel->src[entry_src].src.ssa),
|
|
prev_block)
|
|
->src.ssa);
|
|
|
|
nir_phi_instr_add_src(phi, continue_block,
|
|
nir_phi_get_src_from_block(nir_def_as_phi(bcsel->src[continue_src].src.ssa),
|
|
continue_block)
|
|
->src.ssa);
|
|
|
|
nir_def_init(&phi->instr, &phi->def,
|
|
bcsel->def.num_components,
|
|
bcsel->def.bit_size);
|
|
|
|
b->cursor = nir_after_phis(header_block);
|
|
nir_builder_instr_insert(b, &phi->instr);
|
|
|
|
/* Modify all readers of the bcsel instruction to read the result of
|
|
* the phi.
|
|
*/
|
|
nir_def_rewrite_uses(&bcsel->def,
|
|
&phi->def);
|
|
|
|
/* Since the original bcsel instruction no longer has any readers,
|
|
* just remove it.
|
|
*/
|
|
nir_instr_remove_v(&bcsel->instr);
|
|
nir_instr_free(&bcsel->instr);
|
|
|
|
progress = true;
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
static bool
|
|
is_block_empty(nir_block *block)
|
|
{
|
|
return nir_cf_node_is_last(&block->cf_node) &&
|
|
exec_list_is_empty(&block->instr_list);
|
|
}
|
|
|
|
/* Walk all the phis in the block immediately following the if statement and
|
|
* swap the blocks.
|
|
*/
|
|
static void
|
|
rewrite_phi_predecessor_blocks(nir_if *nif,
|
|
nir_block *old_then_block,
|
|
nir_block *old_else_block,
|
|
nir_block *new_then_block,
|
|
nir_block *new_else_block)
|
|
{
|
|
nir_block *after_if_block =
|
|
nir_cf_node_as_block(nir_cf_node_next(&nif->cf_node));
|
|
|
|
nir_foreach_phi(phi, after_if_block) {
|
|
nir_foreach_phi_src(src, phi) {
|
|
if (src->pred == old_then_block) {
|
|
src->pred = new_then_block;
|
|
} else if (src->pred == old_else_block) {
|
|
src->pred = new_else_block;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* This optimization turns:
|
|
*
|
|
* if (cond) {
|
|
* } else {
|
|
* do_work();
|
|
* }
|
|
*
|
|
* into:
|
|
*
|
|
* if (!cond) {
|
|
* do_work();
|
|
* } else {
|
|
* }
|
|
*/
|
|
static bool
|
|
opt_if_simplification(nir_builder *b, nir_if *nif)
|
|
{
|
|
/* Only simplify if the then block is empty and the else block is not. */
|
|
if (!is_block_empty(nir_if_first_then_block(nif)) ||
|
|
is_block_empty(nir_if_first_else_block(nif)))
|
|
return false;
|
|
|
|
/* Insert the inverted instruction and rewrite the condition. */
|
|
b->cursor = nir_before_src(&nif->condition);
|
|
nir_src_rewrite(&nif->condition, nir_inot(b, nif->condition.ssa));
|
|
|
|
/* Grab pointers to the last then/else blocks for fixing up the phis. */
|
|
nir_block *then_block = nir_if_last_then_block(nif);
|
|
nir_block *else_block = nir_if_last_else_block(nif);
|
|
|
|
if (nir_block_ends_in_jump(else_block)) {
|
|
/* Even though this if statement has a jump on one side, we may still have
|
|
* phis afterwards. Single-source phis can be produced by loop unrolling
|
|
* or dead control-flow passes and are perfectly legal. Run a quick phi
|
|
* removal on the block after the if to clean up any such phis.
|
|
*/
|
|
nir_block *const next_block =
|
|
nir_cf_node_as_block(nir_cf_node_next(&nif->cf_node));
|
|
nir_remove_single_src_phis_block(next_block);
|
|
}
|
|
|
|
rewrite_phi_predecessor_blocks(nif, then_block, else_block, else_block,
|
|
then_block);
|
|
|
|
/* Finally, move the else block to the then block. */
|
|
nir_cf_list tmp;
|
|
nir_cf_extract(&tmp, nir_before_cf_list(&nif->else_list),
|
|
nir_after_cf_list(&nif->else_list));
|
|
nir_cf_reinsert(&tmp, nir_before_cf_list(&nif->then_list));
|
|
|
|
return true;
|
|
}
|
|
|
|
/* Find phi statements after an if that choose between true and false, and
|
|
* replace them with the if statement's condition (or an inot of it).
|
|
*/
|
|
static bool
|
|
opt_if_phi_is_condition(nir_builder *b, nir_if *nif)
|
|
{
|
|
/* Grab pointers to the last then/else blocks for looking in the phis. */
|
|
nir_block *then_block = nir_if_last_then_block(nif);
|
|
ASSERTED nir_block *else_block = nir_if_last_else_block(nif);
|
|
nir_def *cond = nif->condition.ssa;
|
|
bool progress = false;
|
|
|
|
nir_block *after_if_block = nir_cf_node_as_block(nir_cf_node_next(&nif->cf_node));
|
|
nir_foreach_phi_safe(phi, after_if_block) {
|
|
if (phi->def.bit_size != cond->bit_size ||
|
|
phi->def.num_components != 1)
|
|
continue;
|
|
|
|
enum opt_bool {
|
|
T,
|
|
F,
|
|
UNKNOWN
|
|
} then_val = UNKNOWN,
|
|
else_val = UNKNOWN;
|
|
|
|
nir_foreach_phi_src(src, phi) {
|
|
assert(src->pred == then_block || src->pred == else_block);
|
|
enum opt_bool *pred_val = src->pred == then_block ? &then_val : &else_val;
|
|
|
|
nir_scalar val = nir_scalar_resolved(src->src.ssa, 0);
|
|
if (!nir_scalar_is_const(val))
|
|
break;
|
|
|
|
if (nir_scalar_as_int(val) == -1)
|
|
*pred_val = T;
|
|
else if (nir_scalar_as_uint(val) == 0)
|
|
*pred_val = F;
|
|
else
|
|
break;
|
|
}
|
|
if (then_val == T && else_val == F) {
|
|
nir_def_rewrite_uses(&phi->def, cond);
|
|
progress = true;
|
|
} else if (then_val == F && else_val == T) {
|
|
b->cursor = nir_before_cf_node(&nif->cf_node);
|
|
nir_def_rewrite_uses(&phi->def, nir_inot(b, cond));
|
|
progress = true;
|
|
}
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
enum branch_to_eval {
|
|
either_branch,
|
|
then_branch,
|
|
else_branch
|
|
};
|
|
|
|
static bool
|
|
evaluate_if_condition(nir_if *nif, nir_cursor cursor, bool *value, bool invert,
|
|
enum branch_to_eval branch)
|
|
{
|
|
nir_block *use_block = nir_cursor_current_block(cursor);
|
|
if (nir_block_dominates(nir_if_first_then_block(nif), use_block)) {
|
|
if (branch == else_branch)
|
|
return false;
|
|
|
|
*value = !invert;
|
|
return true;
|
|
} else if (nir_block_dominates(nir_if_first_else_block(nif), use_block)) {
|
|
if (branch == then_branch)
|
|
return false;
|
|
|
|
*value = invert;
|
|
return true;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
static nir_def *
|
|
clone_alu_and_replace_src_defs(nir_builder *b, const nir_alu_instr *alu,
|
|
nir_def **src_defs)
|
|
{
|
|
nir_alu_instr *nalu = nir_alu_instr_create(b->shader, alu->op);
|
|
nalu->exact = alu->exact;
|
|
nalu->fp_math_ctrl = alu->fp_math_ctrl;
|
|
|
|
nir_def_init(&nalu->instr, &nalu->def,
|
|
alu->def.num_components,
|
|
alu->def.bit_size);
|
|
|
|
for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
|
|
nalu->src[i].src = nir_src_for_ssa(src_defs[i]);
|
|
memcpy(nalu->src[i].swizzle, alu->src[i].swizzle,
|
|
sizeof(nalu->src[i].swizzle));
|
|
}
|
|
|
|
nir_builder_instr_insert(b, &nalu->instr);
|
|
|
|
return &nalu->def;
|
|
}
|
|
|
|
/*
|
|
* This propagates if condition evaluation down the chain of some alu
|
|
* instructions. For example by checking the use of some of the following alu
|
|
* instruction we can eventually replace ssa_107 with NIR_TRUE.
|
|
*
|
|
* loop {
|
|
* block block_1:
|
|
* vec1 32 ssa_85 = load_const (0x00000002)
|
|
* vec1 32 ssa_86 = ieq ssa_48, ssa_85
|
|
* vec1 32 ssa_87 = load_const (0x00000001)
|
|
* vec1 32 ssa_88 = ieq ssa_48, ssa_87
|
|
* vec1 32 ssa_89 = ior ssa_86, ssa_88
|
|
* vec1 32 ssa_90 = ieq ssa_48, ssa_0
|
|
* vec1 32 ssa_91 = ior ssa_89, ssa_90
|
|
* if ssa_86 {
|
|
* block block_2:
|
|
* ...
|
|
* break
|
|
* } else {
|
|
* block block_3:
|
|
* }
|
|
* block block_4:
|
|
* if ssa_88 {
|
|
* block block_5:
|
|
* ...
|
|
* break
|
|
* } else {
|
|
* block block_6:
|
|
* }
|
|
* block block_7:
|
|
* if ssa_90 {
|
|
* block block_8:
|
|
* ...
|
|
* break
|
|
* } else {
|
|
* block block_9:
|
|
* }
|
|
* block block_10:
|
|
* vec1 32 ssa_107 = inot ssa_91
|
|
* if ssa_107 {
|
|
* block block_11:
|
|
* break
|
|
* } else {
|
|
* block block_12:
|
|
* }
|
|
* }
|
|
*/
|
|
static bool
|
|
propagate_condition_eval(nir_builder *b, nir_if *nif, nir_src *use_src,
|
|
nir_src *alu_use, nir_alu_instr *alu, bool invert,
|
|
enum branch_to_eval branch)
|
|
{
|
|
bool bool_value;
|
|
b->cursor = nir_before_src(alu_use);
|
|
if (!evaluate_if_condition(nif, b->cursor, &bool_value, invert, branch))
|
|
return false;
|
|
|
|
nir_def *def[NIR_MAX_VEC_COMPONENTS] = { 0 };
|
|
for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
|
|
if (alu->src[i].src.ssa == use_src->ssa) {
|
|
def[i] = nir_imm_bool(b, bool_value);
|
|
} else {
|
|
def[i] = alu->src[i].src.ssa;
|
|
}
|
|
}
|
|
|
|
nir_def *nalu = clone_alu_and_replace_src_defs(b, alu, def);
|
|
nir_src_rewrite(alu_use, nalu);
|
|
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* In some cases propagating through a bcsel may be harmful. If the bcsel uses
|
|
* are unlikely to be eliminated in both branch of an if statement,
|
|
* propagating through it may result in extra moves for phi instructions and
|
|
* extended live ranges. The \c ignore_bcsel flag can be used to avoid these
|
|
* cases.
|
|
*/
|
|
static bool
|
|
can_propagate_through_alu(nir_src *src, bool ignore_bcsel)
|
|
{
|
|
if (nir_src_parent_instr(src)->type != nir_instr_type_alu)
|
|
return false;
|
|
|
|
nir_alu_instr *alu = nir_instr_as_alu(nir_src_parent_instr(src));
|
|
switch (alu->op) {
|
|
case nir_op_ior:
|
|
case nir_op_iand:
|
|
case nir_op_inot:
|
|
case nir_op_b2i32:
|
|
return true;
|
|
case nir_op_bcsel:
|
|
return src == &alu->src[0].src && !ignore_bcsel;
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
static bool
|
|
evaluate_condition_use(nir_builder *b, nir_if *nif, nir_src *use_src,
|
|
bool invert, enum branch_to_eval branch)
|
|
{
|
|
bool progress = false;
|
|
|
|
b->cursor = nir_before_src(use_src);
|
|
|
|
bool bool_value;
|
|
if (evaluate_if_condition(nif, b->cursor, &bool_value, invert, branch)) {
|
|
/* Rewrite use to use const */
|
|
nir_src_rewrite(use_src, nir_imm_bool(b, bool_value));
|
|
progress = true;
|
|
}
|
|
|
|
const bool ignore_bcsel = branch != either_branch;
|
|
if (!nir_src_is_if(use_src) && can_propagate_through_alu(use_src,
|
|
ignore_bcsel)) {
|
|
nir_alu_instr *alu = nir_instr_as_alu(nir_src_parent_instr(use_src));
|
|
|
|
nir_foreach_use_including_if_safe(alu_use, &alu->def) {
|
|
progress |= propagate_condition_eval(b, nif, use_src, alu_use, alu,
|
|
invert, branch);
|
|
}
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
static bool
|
|
opt_if_evaluate_condition_use(nir_builder *b, nir_if *nif)
|
|
{
|
|
bool progress = false;
|
|
|
|
/* Evaluate any uses of the if condition inside the if branches */
|
|
nir_foreach_use_including_if_safe(use_src, nif->condition.ssa) {
|
|
if (!(nir_src_is_if(use_src) && nir_src_parent_if(use_src) == nif))
|
|
progress |= evaluate_condition_use(b, nif, use_src, false, either_branch);
|
|
}
|
|
|
|
bool invert = false;
|
|
nir_alu_instr *alu = nir_src_as_alu(nif->condition);
|
|
if (alu != NULL && alu->op == nir_op_inot &&
|
|
nir_src_num_components(alu->src[0].src) == 1) {
|
|
/* Consider
|
|
*
|
|
* if (!x) {
|
|
* if (x) {
|
|
* ...
|
|
* }
|
|
* }
|
|
*
|
|
* The inner use of x must be false, but so far only instances of !x
|
|
* would have been replaced with a constant. See through the inot to
|
|
* replace instances of x as well.
|
|
*/
|
|
nir_foreach_use_including_if_safe(use_src, alu->src[0].src.ssa) {
|
|
if (nir_src_is_if(use_src) || nir_src_parent_instr(use_src) != &alu->instr)
|
|
progress |= evaluate_condition_use(b, nif, use_src, true, either_branch);
|
|
}
|
|
|
|
invert = true;
|
|
alu = nir_src_as_alu(alu->src[0].src);
|
|
}
|
|
|
|
if (alu != NULL) {
|
|
/* For cases like 'if (X && Y)', both X and Y must be true in the then
|
|
* branch. Their values are unknown in the else branch. Similarly, 'if
|
|
* (X || Y)' must have both X and Y false in the else branch.
|
|
*/
|
|
if (alu->op == nir_op_iand || alu->op == nir_op_ior) {
|
|
enum branch_to_eval branch =
|
|
invert != (alu->op == nir_op_ior) ? else_branch : then_branch;
|
|
|
|
for (unsigned i = 0; i < 2; i++) {
|
|
nir_def *def = alu->src[i].src.ssa;
|
|
|
|
if (def->num_components != 1)
|
|
continue;
|
|
|
|
nir_foreach_use_including_if_safe(use_src, def) {
|
|
progress |= evaluate_condition_use(b, nif, use_src,
|
|
invert, branch);
|
|
}
|
|
|
|
/* Just like above, if the op is inot, peel the inot off and try
|
|
* some more.
|
|
*/
|
|
nir_alu_instr *alu_src = nir_src_as_alu(alu->src[i].src);
|
|
if (alu_src != NULL && alu_src->op == nir_op_inot &&
|
|
nir_src_num_components(alu_src->src[0].src) == 1) {
|
|
nir_foreach_use_including_if_safe(use_src, alu_src->src[0].src.ssa) {
|
|
if (nir_src_is_if(use_src) ||
|
|
nir_src_parent_instr(use_src) != &alu_src->instr) {
|
|
progress |= evaluate_condition_use(b, nif, use_src,
|
|
!invert, branch);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
static bool
|
|
rewrite_comp_uses_within_if(nir_builder *b, nir_if *nif, bool invert,
|
|
nir_scalar scalar, nir_scalar new_scalar)
|
|
{
|
|
bool progress = false;
|
|
|
|
nir_block *first = invert ? nir_if_first_else_block(nif) : nir_if_first_then_block(nif);
|
|
nir_block *last = invert ? nir_if_last_else_block(nif) : nir_if_last_then_block(nif);
|
|
|
|
nir_def *new_ssa = NULL;
|
|
nir_foreach_use_safe(use, scalar.def) {
|
|
if (nir_src_parent_instr(use)->block->index < first->index ||
|
|
nir_src_parent_instr(use)->block->index > last->index)
|
|
continue;
|
|
|
|
/* Only rewrite users which use only the new component. This is to avoid a
|
|
* situation where copy propagation will undo the rewrite and we risk an infinite
|
|
* loop.
|
|
*
|
|
* We could rewrite users which use a mix of the old and new components, but if
|
|
* nir_src_components_read() is incomplete, then we risk the new component actually being
|
|
* unused and some optimization later undoing the rewrite.
|
|
*/
|
|
if (nir_src_components_read(use) != BITFIELD64_BIT(scalar.comp))
|
|
continue;
|
|
|
|
if (!new_ssa) {
|
|
b->cursor = nir_before_cf_node(&nif->cf_node);
|
|
new_ssa = nir_mov_scalar(b, new_scalar);
|
|
if (scalar.def->num_components > 1) {
|
|
nir_def *vec = nir_undef(b, scalar.def->num_components, scalar.def->bit_size);
|
|
new_ssa = nir_vector_insert_imm(b, vec, new_ssa, scalar.comp);
|
|
}
|
|
}
|
|
|
|
nir_src_rewrite(use, new_ssa);
|
|
progress = true;
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
/*
|
|
* This optimization turns:
|
|
*
|
|
* if (a == (b=readfirstlane(a)))
|
|
* use(a)
|
|
* if (c == (d=load_const))
|
|
* use(c)
|
|
*
|
|
* into:
|
|
*
|
|
* if (a == (b=readfirstlane(a)))
|
|
* use(b)
|
|
* if (c == (d=load_const))
|
|
* use(d)
|
|
*/
|
|
static bool
|
|
opt_if_rewrite_uniform_uses(nir_builder *b, nir_if *nif, nir_scalar cond, unsigned iand_depth)
|
|
{
|
|
bool progress = false;
|
|
|
|
if (!nir_scalar_is_alu(cond))
|
|
return false;
|
|
|
|
nir_op op = nir_scalar_alu_op(cond);
|
|
if (op == nir_op_iand && iand_depth < 10) {
|
|
progress |= opt_if_rewrite_uniform_uses(b, nif, nir_scalar_chase_alu_src(cond, 0), iand_depth + 1);
|
|
progress |= opt_if_rewrite_uniform_uses(b, nif, nir_scalar_chase_alu_src(cond, 1), iand_depth + 1);
|
|
return progress;
|
|
}
|
|
|
|
if (op != nir_op_ieq && (op != nir_op_ine || iand_depth != 0))
|
|
return false;
|
|
|
|
for (unsigned i = 0; i < 2; i++) {
|
|
nir_scalar src_uni = nir_scalar_chase_alu_src(cond, i);
|
|
nir_scalar src_div = nir_scalar_chase_alu_src(cond, !i);
|
|
|
|
if (nir_scalar_is_const(src_div))
|
|
continue;
|
|
|
|
if (nir_scalar_is_const(src_uni))
|
|
return rewrite_comp_uses_within_if(b, nif, op == nir_op_ine, src_div, src_uni);
|
|
|
|
if (!nir_scalar_is_intrinsic(src_uni))
|
|
continue;
|
|
nir_intrinsic_instr *intrin = nir_def_as_intrinsic(src_uni.def);
|
|
if (intrin->intrinsic != nir_intrinsic_read_first_invocation &&
|
|
intrin->intrinsic != nir_intrinsic_read_invocation &&
|
|
(intrin->intrinsic != nir_intrinsic_reduce || nir_intrinsic_cluster_size(intrin)))
|
|
continue;
|
|
|
|
nir_scalar intrin_src = { intrin->src[0].ssa, src_uni.comp };
|
|
nir_scalar resolved_intrin_src = nir_scalar_resolved(intrin_src.def, intrin_src.comp);
|
|
|
|
if (!nir_scalar_equal(resolved_intrin_src, src_div))
|
|
continue;
|
|
|
|
progress |= rewrite_comp_uses_within_if(b, nif, op == nir_op_ine, resolved_intrin_src, src_uni);
|
|
if (!nir_scalar_equal(intrin_src, resolved_intrin_src))
|
|
progress |= rewrite_comp_uses_within_if(b, nif, op == nir_op_ine, intrin_src, src_uni);
|
|
|
|
return progress;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static void
|
|
simple_merge_if(nir_if *dest_if, nir_if *src_if, bool dest_if_then,
|
|
bool src_if_then)
|
|
{
|
|
/* Now merge the if branch */
|
|
nir_block *dest_blk = dest_if_then ? nir_if_last_then_block(dest_if)
|
|
: nir_if_last_else_block(dest_if);
|
|
|
|
struct exec_list *list = src_if_then ? &src_if->then_list
|
|
: &src_if->else_list;
|
|
|
|
nir_cf_list if_cf_list;
|
|
nir_cf_extract(&if_cf_list, nir_before_cf_list(list),
|
|
nir_after_cf_list(list));
|
|
nir_cf_reinsert(&if_cf_list, nir_after_block(dest_blk));
|
|
}
|
|
|
|
static bool
|
|
opt_phi_src_unused(nir_builder *b, nir_phi_instr *phi,
|
|
nir_if *prev_if, nir_if *next_if)
|
|
{
|
|
/* Return early, if either of the sources is already undef. */
|
|
nir_foreach_phi_src(phi_src, phi) {
|
|
if (nir_src_is_undef(phi_src->src))
|
|
return false;
|
|
}
|
|
|
|
nir_block *first_then = nir_if_first_then_block(next_if);
|
|
nir_block *first_else = nir_if_first_else_block(next_if);
|
|
bool then_used = false;
|
|
bool else_used = false;
|
|
|
|
nir_foreach_use_including_if(use, &phi->def) {
|
|
nir_block *use_block = nir_src_get_block(use);
|
|
|
|
/* Check whether the if_use is on the then- or else- side. */
|
|
if (nir_block_dominates(first_then, use_block))
|
|
then_used = true;
|
|
else if (nir_block_dominates(first_else, use_block))
|
|
else_used = true;
|
|
else
|
|
return false;
|
|
if (then_used && else_used)
|
|
return false;
|
|
}
|
|
|
|
nir_block *unused_blk = then_used ? nir_if_last_else_block(prev_if)
|
|
: nir_if_last_then_block(prev_if);
|
|
nir_src *unused_src = &nir_phi_get_src_from_block(phi, unused_blk)->src;
|
|
|
|
/* Create undef and replace phi-src. */
|
|
b->cursor = nir_before_cf_node(&prev_if->cf_node);
|
|
nir_def *undef = nir_undef(b, phi->def.num_components, phi->def.bit_size);
|
|
nir_src_rewrite(unused_src, undef);
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* This small optimization targets phis between two IF statements with
|
|
* the same condition. If the phi dst is only used in one branch leg,
|
|
* the 'unused' phi source gets replaced with undef.
|
|
*/
|
|
static bool
|
|
opt_if_phi_src_unused(nir_builder *b, nir_if *nif)
|
|
{
|
|
bool progress = false;
|
|
|
|
nir_block *next_blk = nir_cf_node_cf_tree_next(&nif->cf_node);
|
|
nir_if *next_if = nir_block_get_following_if(next_blk);
|
|
if (!next_if || !nir_srcs_equal(nif->condition, next_if->condition))
|
|
return false;
|
|
|
|
nir_foreach_phi(phi, next_blk) {
|
|
progress |= opt_phi_src_unused(b, phi, nif, next_if);
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
static void
|
|
rewrite_phi_uses(nir_phi_instr *phi, nir_if *prev_if, nir_if *next_if)
|
|
{
|
|
nir_def *then_src =
|
|
nir_phi_get_src_from_block(phi, nir_if_last_then_block(prev_if))->src.ssa;
|
|
nir_def *else_src =
|
|
nir_phi_get_src_from_block(phi, nir_if_last_else_block(prev_if))->src.ssa;
|
|
|
|
/* Rewrite all uses inside the next IF with either then_src or else_src. */
|
|
nir_foreach_use_including_if_safe(use, &phi->def) {
|
|
nir_cf_node *node = &nir_src_get_block(use)->cf_node;
|
|
|
|
/* Check if the node is inside the if-stmt. */
|
|
while (node) {
|
|
if (node->parent == &next_if->cf_node)
|
|
break;
|
|
|
|
node = node->parent;
|
|
if (node == prev_if->cf_node.parent)
|
|
node = NULL;
|
|
}
|
|
|
|
/* The node is outside of the IF. */
|
|
if (!node)
|
|
continue;
|
|
|
|
/* Get the first block. */
|
|
while (!nir_cf_node_is_first(node))
|
|
node = nir_cf_node_prev(node);
|
|
|
|
nir_block *block = nir_cf_node_as_block(node);
|
|
nir_src_rewrite(use, block == nir_if_first_then_block(next_if) ? then_src : else_src);
|
|
}
|
|
}
|
|
|
|
static bool
|
|
opt_if_merge(nir_if *nif)
|
|
{
|
|
nir_block *next_blk = nir_cf_node_cf_tree_next(&nif->cf_node);
|
|
if (!next_blk)
|
|
return false;
|
|
|
|
nir_if *next_if = nir_block_get_following_if(next_blk);
|
|
if (!next_if || !nir_srcs_equal(nif->condition, next_if->condition))
|
|
return false;
|
|
|
|
/* This optimization isn't made to work in this case and
|
|
* opt_if_evaluate_condition_use will optimize it later.
|
|
*/
|
|
if (nir_block_ends_in_jump(nir_if_last_then_block(nif)) ||
|
|
nir_block_ends_in_jump(nir_if_last_else_block(nif)))
|
|
return false;
|
|
|
|
/* This optimization is not prepared to handle updating phis other than
|
|
* immediately after the second if-statement.
|
|
*/
|
|
if (nir_block_ends_in_jump(nir_if_last_then_block(next_if)) ||
|
|
nir_block_ends_in_jump(nir_if_last_else_block(next_if)))
|
|
return false;
|
|
|
|
/* Ensure that there is nothing but phis between the IFs */
|
|
if (!exec_list_is_empty(&next_blk->instr_list)) {
|
|
if (nir_block_last_instr(next_blk)->type != nir_instr_type_phi)
|
|
return false;
|
|
|
|
/* If there are phis, then the next IF must not contain any jump. */
|
|
nir_foreach_block_in_cf_node(block, &next_if->cf_node) {
|
|
if (nir_block_ends_in_jump(block))
|
|
return false;
|
|
}
|
|
}
|
|
|
|
nir_foreach_phi(phi, next_blk) {
|
|
/* Rewrite the phi uses in each branch leg of the following IF
|
|
* with the phi source from the respective branch leg of the
|
|
* previous IF.
|
|
*/
|
|
rewrite_phi_uses(phi, nif, next_if);
|
|
}
|
|
|
|
/* Here we merge two consecutive ifs that have the same condition e.g:
|
|
*
|
|
* if ssa_12 {
|
|
* ...
|
|
* } else {
|
|
* ...
|
|
* }
|
|
* if ssa_12 {
|
|
* ...
|
|
* } else {
|
|
* ...
|
|
* }
|
|
*
|
|
* Note: This only merges if-statements when the block between them is
|
|
* empty except for phis.
|
|
*/
|
|
simple_merge_if(nif, next_if, true, true);
|
|
simple_merge_if(nif, next_if, false, false);
|
|
|
|
nir_block *new_then_block = nir_if_last_then_block(nif);
|
|
nir_block *new_else_block = nir_if_last_else_block(nif);
|
|
|
|
nir_block *old_then_block = nir_if_last_then_block(next_if);
|
|
nir_block *old_else_block = nir_if_last_else_block(next_if);
|
|
|
|
/* Rewrite the predecessor block for any phis following the second
|
|
* if-statement.
|
|
*/
|
|
rewrite_phi_predecessor_blocks(next_if, old_then_block,
|
|
old_else_block,
|
|
new_then_block,
|
|
new_else_block);
|
|
|
|
/* Move phis after merged if to avoid them being deleted when we remove
|
|
* the merged if-statement.
|
|
*/
|
|
nir_block *after_next_if_block =
|
|
nir_cf_node_as_block(nir_cf_node_next(&next_if->cf_node));
|
|
|
|
nir_foreach_phi_safe(phi, after_next_if_block) {
|
|
exec_node_remove(&phi->instr.node);
|
|
exec_list_push_tail(&next_blk->instr_list, &phi->instr.node);
|
|
phi->instr.block = next_blk;
|
|
}
|
|
|
|
nir_cf_node_remove(&next_if->cf_node);
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool
|
|
opt_if_cf_list(nir_builder *b, struct exec_list *cf_list,
|
|
nir_opt_if_options options)
|
|
{
|
|
bool progress = false;
|
|
foreach_list_typed(nir_cf_node, cf_node, node, 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);
|
|
progress |= opt_if_cf_list(b, &nif->then_list,
|
|
options);
|
|
progress |= opt_if_cf_list(b, &nif->else_list,
|
|
options);
|
|
progress |= opt_if_merge(nif);
|
|
progress |= opt_if_simplification(b, nif);
|
|
if (options & nir_opt_if_optimize_phi_true_false)
|
|
progress |= opt_if_phi_is_condition(b, nif);
|
|
break;
|
|
}
|
|
|
|
case nir_cf_node_loop: {
|
|
nir_loop *loop = nir_cf_node_as_loop(cf_node);
|
|
assert(!nir_loop_has_continue_construct(loop));
|
|
progress |= opt_if_cf_list(b, &loop->body,
|
|
options);
|
|
progress |= opt_simplify_bcsel_of_phi(b, loop);
|
|
break;
|
|
}
|
|
|
|
case nir_cf_node_function:
|
|
UNREACHABLE("Invalid cf type");
|
|
}
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
/**
|
|
* Optimizations which can create registers are done after other optimizations
|
|
* which require SSA.
|
|
*/
|
|
static bool
|
|
opt_if_regs_cf_list(struct exec_list *cf_list)
|
|
{
|
|
bool progress = false;
|
|
foreach_list_typed(nir_cf_node, cf_node, node, 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);
|
|
progress |= opt_if_regs_cf_list(&nif->then_list);
|
|
progress |= opt_if_regs_cf_list(&nif->else_list);
|
|
break;
|
|
}
|
|
|
|
case nir_cf_node_loop: {
|
|
nir_loop *loop = nir_cf_node_as_loop(cf_node);
|
|
assert(!nir_loop_has_continue_construct(loop));
|
|
progress |= opt_if_regs_cf_list(&loop->body);
|
|
progress |= opt_peel_loop_initial_if(loop);
|
|
break;
|
|
}
|
|
|
|
case nir_cf_node_function:
|
|
UNREACHABLE("Invalid cf type");
|
|
}
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
/**
|
|
* These optimisations depend on nir_metadata_block_index and therefore must
|
|
* not do anything to cause the metadata to become invalid.
|
|
*/
|
|
static bool
|
|
opt_if_safe_cf_list(nir_builder *b, struct exec_list *cf_list, nir_opt_if_options options)
|
|
{
|
|
bool progress = false;
|
|
foreach_list_typed(nir_cf_node, cf_node, node, 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);
|
|
progress |= opt_if_safe_cf_list(b, &nif->then_list, options);
|
|
progress |= opt_if_safe_cf_list(b, &nif->else_list, options);
|
|
progress |= opt_if_evaluate_condition_use(b, nif);
|
|
nir_scalar cond = nir_scalar_resolved(nif->condition.ssa, 0);
|
|
progress |= opt_if_rewrite_uniform_uses(b, nif, cond, 0);
|
|
progress |= opt_if_phi_src_unused(b, nif);
|
|
break;
|
|
}
|
|
|
|
case nir_cf_node_loop: {
|
|
nir_loop *loop = nir_cf_node_as_loop(cf_node);
|
|
assert(!nir_loop_has_continue_construct(loop));
|
|
progress |= opt_if_safe_cf_list(b, &loop->body, options);
|
|
progress |= opt_split_alu_of_phi(b, loop, options);
|
|
break;
|
|
}
|
|
|
|
case nir_cf_node_function:
|
|
UNREACHABLE("Invalid cf type");
|
|
}
|
|
}
|
|
|
|
return progress;
|
|
}
|
|
|
|
static bool
|
|
nir_opt_if_impl(nir_function_impl *impl, nir_opt_if_options options)
|
|
{
|
|
nir_builder b = nir_builder_create(impl);
|
|
nir_metadata_require(impl,
|
|
nir_metadata_block_index | nir_metadata_dominance);
|
|
|
|
bool progress_safe = opt_if_safe_cf_list(&b, &impl->body, options);
|
|
nir_progress(progress_safe, impl, nir_metadata_control_flow);
|
|
|
|
bool progress = opt_if_cf_list(&b, &impl->body, options);
|
|
bool progress_regs = opt_if_regs_cf_list(&impl->body);
|
|
nir_progress(progress || progress_regs, impl, nir_metadata_none);
|
|
|
|
if (progress_regs) {
|
|
/* If that made progress, we're no longer really in SSA form. We
|
|
* need to convert registers back into SSA defs and clean up SSA defs
|
|
* that don't dominate their uses.
|
|
*/
|
|
nir_lower_reg_intrinsics_to_ssa_impl(impl);
|
|
}
|
|
|
|
return progress_safe || progress || progress_regs;
|
|
}
|
|
|
|
bool
|
|
nir_opt_if(nir_shader *shader, nir_opt_if_options options)
|
|
{
|
|
bool progress = false;
|
|
|
|
nir_foreach_function_impl(impl, shader)
|
|
progress |= nir_opt_if_impl(impl, options);
|
|
|
|
return progress;
|
|
}
|