[transform] Add first index offset transform
Adding new transform to workaround D3D's vertex/instance_index always
starting from 0
Bug: dawn:548
Change-Id: I048f39e76e236570f3ce337a77d804384ee659a4
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/34600
Commit-Queue: Enrico Galli <enrico.galli@intel.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
diff --git a/src/transform/first_index_offset.cc b/src/transform/first_index_offset.cc
new file mode 100644
index 0000000..fcca0c6
--- /dev/null
+++ b/src/transform/first_index_offset.cc
@@ -0,0 +1,225 @@
+// Copyright 2020 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/transform/first_index_offset.h"
+
+#include <cassert>
+#include <utility>
+
+#include "src/ast/array_accessor_expression.h"
+#include "src/ast/assignment_statement.h"
+#include "src/ast/binary_expression.h"
+#include "src/ast/bitcast_expression.h"
+#include "src/ast/break_statement.h"
+#include "src/ast/builtin_decoration.h"
+#include "src/ast/call_statement.h"
+#include "src/ast/case_statement.h"
+#include "src/ast/constructor_expression.h"
+#include "src/ast/decorated_variable.h"
+#include "src/ast/else_statement.h"
+#include "src/ast/expression.h"
+#include "src/ast/fallthrough_statement.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/if_statement.h"
+#include "src/ast/loop_statement.h"
+#include "src/ast/member_accessor_expression.h"
+#include "src/ast/return_statement.h"
+#include "src/ast/scalar_constructor_expression.h"
+#include "src/ast/struct.h"
+#include "src/ast/struct_block_decoration.h"
+#include "src/ast/struct_decoration.h"
+#include "src/ast/struct_member.h"
+#include "src/ast/struct_member_offset_decoration.h"
+#include "src/ast/switch_statement.h"
+#include "src/ast/type/struct_type.h"
+#include "src/ast/type/u32_type.h"
+#include "src/ast/type_constructor_expression.h"
+#include "src/ast/unary_op_expression.h"
+#include "src/ast/variable.h"
+#include "src/ast/variable_decl_statement.h"
+#include "src/ast/variable_decoration.h"
+#include "src/type_determiner.h"
+
+namespace tint {
+namespace transform {
+namespace {
+
+constexpr char kStructName[] = "TintFirstIndexOffsetData";
+constexpr char kBufferName[] = "tint_first_index_data";
+constexpr char kFirstVertexName[] = "tint_first_vertex_index";
+constexpr char kFirstInstanceName[] = "tint_first_instance_index";
+constexpr char kIndexOffsetPrefix[] = "tint_first_index_offset_";
+
+} // namespace
+
+FirstIndexOffset::FirstIndexOffset(uint32_t binding, uint32_t set)
+ : binding_(binding), set_(set) {}
+
+FirstIndexOffset::~FirstIndexOffset() = default;
+
+Transform::Output FirstIndexOffset::Run(ast::Module* in) {
+ Output out;
+ out.module = in->Clone();
+ auto* mod = &out.module;
+
+ // Running TypeDeterminer as we require local_referenced_builtin_variables()
+ // to be populated
+ TypeDeterminer td(mod);
+ if (!td.Determine()) {
+ diag::Diagnostic err;
+ err.severity = diag::Severity::Error;
+ err.message = td.error();
+ out.diagnostics.add(std::move(err));
+ return out;
+ }
+
+ std::string vertex_index_name;
+ std::string instance_index_name;
+
+ for (ast::Variable* var : mod->global_variables()) {
+ if (auto* dec_var = var->As<ast::DecoratedVariable>()) {
+ if (dec_var->name() == kBufferName) {
+ diag::Diagnostic err;
+ err.message = "First index offset transform has already been applied.";
+ err.severity = diag::Severity::Error;
+ out.diagnostics.add(std::move(err));
+ return out;
+ }
+
+ for (ast::VariableDecoration* dec : dec_var->decorations()) {
+ if (auto* blt_dec = dec->As<ast::BuiltinDecoration>()) {
+ ast::Builtin blt_type = blt_dec->value();
+ if (blt_type == ast::Builtin::kVertexIdx) {
+ vertex_index_name = var->name();
+ var->set_name(kIndexOffsetPrefix + var->name());
+ has_vertex_index_ = true;
+ } else if (blt_type == ast::Builtin::kInstanceIdx) {
+ instance_index_name = var->name();
+ var->set_name(kIndexOffsetPrefix + var->name());
+ has_instance_index_ = true;
+ }
+ }
+ }
+ }
+ }
+
+ if (!has_vertex_index_ && !has_instance_index_) {
+ return out;
+ }
+
+ ast::Variable* buffer_var = AddUniformBuffer(mod);
+
+ for (ast::Function* func : mod->functions()) {
+ for (const auto& data : func->local_referenced_builtin_variables()) {
+ if (data.second->value() == ast::Builtin::kVertexIdx) {
+ AddFirstIndexOffset(vertex_index_name, kFirstVertexName, buffer_var,
+ func, mod);
+ } else if (data.second->value() == ast::Builtin::kInstanceIdx) {
+ AddFirstIndexOffset(instance_index_name, kFirstInstanceName, buffer_var,
+ func, mod);
+ }
+ }
+ }
+
+ return out;
+}
+
+bool FirstIndexOffset::HasVertexIndex() {
+ return has_vertex_index_;
+}
+
+bool FirstIndexOffset::HasInstanceIndex() {
+ return has_instance_index_;
+}
+
+uint32_t FirstIndexOffset::GetFirstVertexOffset() {
+ assert(has_vertex_index_);
+ return vertex_index_offset_;
+}
+
+uint32_t FirstIndexOffset::GetFirstInstanceOffset() {
+ assert(has_instance_index_);
+ return instance_index_offset_;
+}
+
+ast::Variable* FirstIndexOffset::AddUniformBuffer(ast::Module* mod) {
+ auto* u32_type = mod->create<ast::type::U32>();
+ ast::StructMemberList members;
+ uint32_t offset = 0;
+ if (has_vertex_index_) {
+ ast::StructMemberDecorationList member_dec;
+ member_dec.push_back(
+ mod->create<ast::StructMemberOffsetDecoration>(offset, Source{}));
+ members.push_back(mod->create<ast::StructMember>(kFirstVertexName, u32_type,
+ std::move(member_dec)));
+ vertex_index_offset_ = offset;
+ offset += 4;
+ }
+
+ if (has_instance_index_) {
+ ast::StructMemberDecorationList member_dec;
+ member_dec.push_back(
+ mod->create<ast::StructMemberOffsetDecoration>(offset, Source{}));
+ members.push_back(mod->create<ast::StructMember>(
+ kFirstInstanceName, u32_type, std::move(member_dec)));
+ instance_index_offset_ = offset;
+ offset += 4;
+ }
+
+ ast::StructDecorationList decos;
+ decos.push_back(mod->create<ast::StructBlockDecoration>(Source{}));
+
+ auto* struct_type = mod->create<ast::type::Struct>(
+ kStructName,
+ mod->create<ast::Struct>(std::move(decos), std::move(members)));
+
+ auto* idx_var =
+ mod->create<ast::DecoratedVariable>(mod->create<ast::Variable>(
+ Source{}, kBufferName, ast::StorageClass::kUniform, struct_type));
+
+ ast::VariableDecorationList decorations;
+ decorations.push_back(
+ mod->create<ast::BindingDecoration>(binding_, Source{}));
+ decorations.push_back(mod->create<ast::SetDecoration>(set_, Source{}));
+ idx_var->set_decorations(std::move(decorations));
+
+ mod->AddGlobalVariable(idx_var);
+
+ mod->AddConstructedType(struct_type);
+
+ return idx_var;
+}
+
+void FirstIndexOffset::AddFirstIndexOffset(const std::string& original_name,
+ const std::string& field_name,
+ ast::Variable* buffer_var,
+ ast::Function* func,
+ ast::Module* mod) {
+ auto* buffer = mod->create<ast::IdentifierExpression>(buffer_var->name());
+ auto* var = mod->create<ast::Variable>(Source{}, original_name,
+ ast::StorageClass::kNone,
+ mod->create<ast::type::U32>());
+
+ var->set_is_const(true);
+ var->set_constructor(mod->create<ast::BinaryExpression>(
+ ast::BinaryOp::kAdd,
+ mod->create<ast::IdentifierExpression>(kIndexOffsetPrefix + var->name()),
+ mod->create<ast::MemberAccessorExpression>(
+ buffer, mod->create<ast::IdentifierExpression>(field_name))));
+ func->body()->insert(0,
+ mod->create<ast::VariableDeclStatement>(std::move(var)));
+}
+
+} // namespace transform
+} // namespace tint
