288 lines
11 KiB
C
288 lines
11 KiB
C
/*
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* Copyright © 2015 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.h"
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#include "nir_builder.h"
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#include "nir_control_flow.h"
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#include "nir_vla.h"
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static bool function_ends_in_jump(nir_function_impl *impl)
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{
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nir_block *last_block = nir_impl_last_block(impl);
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return nir_block_ends_in_jump(last_block);
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}
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void nir_inline_function_impl(struct nir_builder *b,
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const nir_function_impl *impl,
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nir_ssa_def **params,
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struct hash_table *shader_var_remap)
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{
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nir_function_impl *copy = nir_function_impl_clone(b->shader, impl);
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exec_list_append(&b->impl->locals, ©->locals);
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exec_list_append(&b->impl->registers, ©->registers);
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nir_foreach_block(block, copy) {
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nir_foreach_instr_safe(instr, block) {
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switch (instr->type) {
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case nir_instr_type_deref: {
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nir_deref_instr *deref = nir_instr_as_deref(instr);
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if (deref->deref_type != nir_deref_type_var)
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break;
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/* We don't need to remap function variables. We already cloned
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* them as part of nir_function_impl_clone and appended them to
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* b->impl->locals.
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*/
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if (deref->var->data.mode == nir_var_function_temp)
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break;
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/* If no map is provided, we assume that there are either no
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* shader variables or they already live b->shader (this is the
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* case for function inlining within a single shader.
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*/
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if (shader_var_remap == NULL)
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break;
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struct hash_entry *entry =
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_mesa_hash_table_search(shader_var_remap, deref->var);
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if (entry == NULL) {
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nir_variable *nvar = nir_variable_clone(deref->var, b->shader);
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nir_shader_add_variable(b->shader, nvar);
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entry = _mesa_hash_table_insert(shader_var_remap,
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deref->var, nvar);
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}
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deref->var = entry->data;
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break;
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}
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case nir_instr_type_intrinsic: {
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nir_intrinsic_instr *load = nir_instr_as_intrinsic(instr);
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if (load->intrinsic != nir_intrinsic_load_param)
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break;
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unsigned param_idx = nir_intrinsic_param_idx(load);
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assert(param_idx < impl->function->num_params);
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assert(load->dest.is_ssa);
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nir_ssa_def_rewrite_uses(&load->dest.ssa,
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params[param_idx]);
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/* Remove any left-over load_param intrinsics because they're soon
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* to be in another function and therefore no longer valid.
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*/
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nir_instr_remove(&load->instr);
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break;
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}
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case nir_instr_type_jump:
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/* Returns have to be lowered for this to work */
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assert(nir_instr_as_jump(instr)->type != nir_jump_return);
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break;
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default:
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break;
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}
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}
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}
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bool nest_if = function_ends_in_jump(copy);
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/* Pluck the body out of the function and place it here */
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nir_cf_list body;
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nir_cf_list_extract(&body, ©->body);
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if (nest_if) {
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nir_if *cf = nir_push_if(b, nir_imm_bool(b, true));
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nir_cf_reinsert(&body, nir_after_cf_list(&cf->then_list));
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nir_pop_if(b, cf);
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} else {
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/* Insert a nop at the cursor so we can keep track of where things are as
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* we add/remove stuff from the CFG.
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*/
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nir_intrinsic_instr *nop = nir_nop(b);
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nir_cf_reinsert(&body, nir_before_instr(&nop->instr));
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b->cursor = nir_instr_remove(&nop->instr);
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}
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}
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static bool inline_function_impl(nir_function_impl *impl, struct set *inlined);
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static bool
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inline_functions_block(nir_block *block, nir_builder *b,
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struct set *inlined)
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{
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bool progress = false;
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/* This is tricky. We're iterating over instructions in a block but, as
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* we go, the block and its instruction list are being split into
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* pieces. However, this *should* be safe since foreach_safe always
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* stashes the next thing in the iteration. That next thing will
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* properly get moved to the next block when it gets split, and we
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* continue iterating there.
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*/
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nir_foreach_instr_safe(instr, block) {
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if (instr->type != nir_instr_type_call)
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continue;
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progress = true;
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nir_call_instr *call = nir_instr_as_call(instr);
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assert(call->callee->impl);
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/* Make sure that the function we're calling is already inlined */
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inline_function_impl(call->callee->impl, inlined);
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b->cursor = nir_instr_remove(&call->instr);
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/* Rewrite all of the uses of the callee's parameters to use the call
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* instructions sources. In order to ensure that the "load" happens
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* here and not later (for register sources), we make sure to convert it
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* to an SSA value first.
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*/
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const unsigned num_params = call->num_params;
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NIR_VLA(nir_ssa_def *, params, num_params);
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for (unsigned i = 0; i < num_params; i++) {
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params[i] = nir_ssa_for_src(b, call->params[i],
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call->callee->params[i].num_components);
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}
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nir_inline_function_impl(b, call->callee->impl, params, NULL);
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}
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return progress;
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}
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static bool
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inline_function_impl(nir_function_impl *impl, struct set *inlined)
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{
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if (_mesa_set_search(inlined, impl))
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return false; /* Already inlined */
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nir_builder b;
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nir_builder_init(&b, impl);
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bool progress = false;
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nir_foreach_block_safe(block, impl) {
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progress |= inline_functions_block(block, &b, inlined);
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}
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if (progress) {
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/* SSA and register indices are completely messed up now */
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nir_index_ssa_defs(impl);
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nir_index_local_regs(impl);
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nir_metadata_preserve(impl, nir_metadata_none);
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} else {
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nir_metadata_preserve(impl, nir_metadata_all);
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}
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_mesa_set_add(inlined, impl);
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return progress;
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}
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/** A pass to inline all functions in a shader into their callers
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*
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* For most use-cases, function inlining is a multi-step process. The general
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* pattern employed by SPIR-V consumers and others is as follows:
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*
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* 1. nir_lower_variable_initializers(shader, nir_var_function_temp)
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*
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* This is needed because local variables from the callee are simply added
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* to the locals list for the caller and the information about where the
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* constant initializer logically happens is lost. If the callee is
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* called in a loop, this can cause the variable to go from being
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* initialized once per loop iteration to being initialized once at the
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* top of the caller and values to persist from one invocation of the
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* callee to the next. The simple solution to this problem is to get rid
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* of constant initializers before function inlining.
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*
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* 2. nir_lower_returns(shader)
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*
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* nir_inline_functions assumes that all functions end "naturally" by
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* execution reaching the end of the function without any return
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* instructions causing instant jumps to the end. Thanks to NIR being
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* structured, we can't represent arbitrary jumps to various points in the
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* program which is what an early return in the callee would have to turn
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* into when we inline it into the caller. Instead, we require returns to
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* be lowered which lets us just copy+paste the callee directly into the
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* caller.
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*
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* 3. nir_inline_functions(shader)
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*
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* This does the actual function inlining and the resulting shader will
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* contain no call instructions.
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*
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* 4. nir_opt_deref(shader)
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*
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* Most functions contain pointer parameters where the result of a deref
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* instruction is passed in as a parameter, loaded via a load_param
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* intrinsic, and then turned back into a deref via a cast. Function
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* inlining will get rid of the load_param but we are still left with a
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* cast. Running nir_opt_deref gets rid of the intermediate cast and
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* results in a whole deref chain again. This is currently required by a
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* number of optimizations and lowering passes at least for certain
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* variable modes.
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*
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* 5. Loop over the functions and delete all but the main entrypoint.
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*
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* In the Intel Vulkan driver this looks like this:
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*
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* foreach_list_typed_safe(nir_function, func, node, &nir->functions) {
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* if (func != entry_point)
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* exec_node_remove(&func->node);
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* }
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* assert(exec_list_length(&nir->functions) == 1);
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*
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* While nir_inline_functions does get rid of all call instructions, it
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* doesn't get rid of any functions because it doesn't know what the "root
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* function" is. Instead, it's up to the individual driver to know how to
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* decide on a root function and delete the rest. With SPIR-V,
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* spirv_to_nir returns the root function and so we can just use == whereas
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* with GL, you may have to look for a function named "main".
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*
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* 6. nir_lower_variable_initializers(shader, ~nir_var_function_temp)
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*
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* Lowering constant initializers on inputs, outputs, global variables,
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* etc. requires that we know the main entrypoint so that we know where to
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* initialize them. Otherwise, we would have to assume that anything
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* could be a main entrypoint and initialize them at the start of every
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* function but that would clearly be wrong if any of those functions were
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* ever called within another function. Simply requiring a single-
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* entrypoint function shader is the best way to make it well-defined.
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*/
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bool
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nir_inline_functions(nir_shader *shader)
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{
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struct set *inlined = _mesa_pointer_set_create(NULL);
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bool progress = false;
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nir_foreach_function(function, shader) {
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if (function->impl)
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progress = inline_function_impl(function->impl, inlined) || progress;
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}
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_mesa_set_destroy(inlined, NULL);
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return progress;
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}
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