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// Copyright 2021 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/tint/transform/module_scope_var_to_entry_point_param.h"
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#include "src/tint/ast/disable_validation_attribute.h"
#include "src/tint/program_builder.h"
#include "src/tint/sem/call.h"
#include "src/tint/sem/function.h"
#include "src/tint/sem/module.h"
#include "src/tint/sem/statement.h"
#include "src/tint/sem/variable.h"
#include "src/tint/utils/string.h"
TINT_INSTANTIATE_TYPEINFO(tint::transform::ModuleScopeVarToEntryPointParam);
namespace tint::transform {
namespace {
using WorkgroupParameterMemberList = utils::Vector<const ast::StructMember*, 8>;
// The name of the struct member for arrays that are wrapped in structures.
const char* kWrappedArrayMemberName = "arr";
bool ShouldRun(const Program* program) {
for (auto* decl : program->AST().GlobalDeclarations()) {
if (decl->Is<ast::Variable>()) {
return true;
}
}
return false;
}
// Returns `true` if `type` is or contains a matrix type.
bool ContainsMatrix(const sem::Type* type) {
type = type->UnwrapRef();
if (type->Is<sem::Matrix>()) {
return true;
} else if (auto* ary = type->As<sem::Array>()) {
return ContainsMatrix(ary->ElemType());
} else if (auto* str = type->As<sem::Struct>()) {
for (auto* member : str->Members()) {
if (ContainsMatrix(member->Type())) {
return true;
}
}
}
return false;
}
} // namespace
/// PIMPL state for the transform
struct ModuleScopeVarToEntryPointParam::State {
/// The clone context.
CloneContext& ctx;
/// Constructor
/// @param context the clone context
explicit State(CloneContext& context) : ctx(context) {}
/// Clone any struct types that are contained in `ty` (including `ty` itself),
/// and add it to the global declarations now, so that they precede new global
/// declarations that need to reference them.
/// @param ty the type to clone
void CloneStructTypes(const sem::Type* ty) {
if (auto* str = ty->As<sem::Struct>()) {
if (!cloned_structs_.emplace(str).second) {
// The struct has already been cloned.
return;
}
// Recurse into members.
for (auto* member : str->Members()) {
CloneStructTypes(member->Type());
}
// Clone the struct and add it to the global declaration list.
// Remove the old declaration.
auto* ast_str = str->Declaration();
ctx.dst->AST().AddTypeDecl(ctx.Clone(ast_str));
ctx.Remove(ctx.src->AST().GlobalDeclarations(), ast_str);
} else if (auto* arr = ty->As<sem::Array>()) {
CloneStructTypes(arr->ElemType());
}
}
/// Process a variable `var` that is referenced in the entry point function `func`.
/// This will redeclare the variable as a function parameter, possibly as a pointer.
/// Some workgroup variables will be redeclared as a member inside a workgroup structure.
/// @param func the entry point function
/// @param var the variable
/// @param new_var_symbol the symbol to use for the replacement
/// @param workgroup_param helper function to get a symbol to a workgroup struct parameter
/// @param workgroup_parameter_members reference to a list of a workgroup struct members
/// @param is_pointer output signalling whether the replacement is a pointer
/// @param is_wrapped output signalling whether the replacement is wrapped in a struct
void ProcessVariableInEntryPoint(const ast::Function* func,
const sem::Variable* var,
Symbol new_var_symbol,
std::function<Symbol()> workgroup_param,
WorkgroupParameterMemberList& workgroup_parameter_members,
bool& is_pointer,
bool& is_wrapped) {
auto* var_ast = var->Declaration()->As<ast::Var>();
auto* ty = var->Type()->UnwrapRef();
// Helper to create an AST node for the store type of the variable.
auto store_type = [&]() { return CreateASTTypeFor(ctx, ty); };
ast::AddressSpace sc = var->AddressSpace();
switch (sc) {
case ast::AddressSpace::kHandle: {
// For a texture or sampler variable, redeclare it as an entry point parameter.
// Disable entry point parameter validation.
auto* disable_validation =
ctx.dst->Disable(ast::DisabledValidation::kEntryPointParameter);
auto attrs = ctx.Clone(var->Declaration()->attributes);
attrs.Push(disable_validation);
auto* param = ctx.dst->Param(new_var_symbol, store_type(), attrs);
ctx.InsertFront(func->params, param);
break;
}
case ast::AddressSpace::kStorage:
case ast::AddressSpace::kUniform: {
// Variables into the Storage and Uniform address spacees are redeclared as entry
// point parameters with a pointer type.
auto attributes = ctx.Clone(var->Declaration()->attributes);
attributes.Push(ctx.dst->Disable(ast::DisabledValidation::kEntryPointParameter));
attributes.Push(ctx.dst->Disable(ast::DisabledValidation::kIgnoreAddressSpace));
auto* param_type = store_type();
if (auto* arr = ty->As<sem::Array>(); arr && arr->IsRuntimeSized()) {
// Wrap runtime-sized arrays in structures, so that we can declare pointers to
// them. Ideally we'd just emit the array itself as a pointer, but this is not
// representable in Tint's AST.
CloneStructTypes(ty);
auto* wrapper = ctx.dst->Structure(
ctx.dst->Sym(), utils::Vector{
ctx.dst->Member(kWrappedArrayMemberName, param_type),
});
param_type = ctx.dst->ty.Of(wrapper);
is_wrapped = true;
}
param_type = ctx.dst->ty.pointer(param_type, sc, var_ast->declared_access);
auto* param = ctx.dst->Param(new_var_symbol, param_type, attributes);
ctx.InsertFront(func->params, param);
is_pointer = true;
break;
}
case ast::AddressSpace::kWorkgroup: {
if (ContainsMatrix(var->Type())) {
// Due to a bug in the MSL compiler, we use a threadgroup memory argument for
// any workgroup allocation that contains a matrix. See crbug.com/tint/938.
// TODO(jrprice): Do this for all other workgroup variables too.
// Create a member in the workgroup parameter struct.
auto member = ctx.Clone(var->Declaration()->symbol);
workgroup_parameter_members.Push(ctx.dst->Member(member, store_type()));
CloneStructTypes(var->Type()->UnwrapRef());
// Create a function-scope variable that is a pointer to the member.
auto* member_ptr = ctx.dst->AddressOf(
ctx.dst->MemberAccessor(ctx.dst->Deref(workgroup_param()), member));
auto* local_var = ctx.dst->Let(
new_var_symbol,
ctx.dst->ty.pointer(store_type(), ast::AddressSpace::kWorkgroup),
member_ptr);
ctx.InsertFront(func->body->statements, ctx.dst->Decl(local_var));
is_pointer = true;
break;
}
[[fallthrough]];
}
case ast::AddressSpace::kPrivate: {
// Variables in the Private and Workgroup address spacees are redeclared at function
// scope. Disable address space validation on this variable.
auto* disable_validation =
ctx.dst->Disable(ast::DisabledValidation::kIgnoreAddressSpace);
auto* initializer = ctx.Clone(var->Declaration()->initializer);
auto* local_var = ctx.dst->Var(new_var_symbol, store_type(), sc, initializer,
utils::Vector{disable_validation});
ctx.InsertFront(func->body->statements, ctx.dst->Decl(local_var));
break;
}
case ast::AddressSpace::kPushConstant: {
ctx.dst->Diagnostics().add_error(
diag::System::Transform,
"unhandled module-scope address space (" + utils::ToString(sc) + ")");
break;
}
default: {
TINT_ICE(Transform, ctx.dst->Diagnostics())
<< "unhandled module-scope address space (" << sc << ")";
break;
}
}
}
/// Process a variable `var` that is referenced in the user-defined function `func`.
/// This will redeclare the variable as a function parameter, possibly as a pointer.
/// @param func the user-defined function
/// @param var the variable
/// @param new_var_symbol the symbol to use for the replacement
/// @param is_pointer output signalling whether the replacement is a pointer or not
void ProcessVariableInUserFunction(const ast::Function* func,
const sem::Variable* var,
Symbol new_var_symbol,
bool& is_pointer) {
auto* var_ast = var->Declaration()->As<ast::Var>();
auto* ty = var->Type()->UnwrapRef();
auto* param_type = CreateASTTypeFor(ctx, ty);
auto sc = var->AddressSpace();
switch (sc) {
case ast::AddressSpace::kPrivate:
case ast::AddressSpace::kStorage:
case ast::AddressSpace::kUniform:
case ast::AddressSpace::kHandle:
case ast::AddressSpace::kWorkgroup:
break;
case ast::AddressSpace::kPushConstant: {
ctx.dst->Diagnostics().add_error(
diag::System::Transform,
"unhandled module-scope address space (" + utils::ToString(sc) + ")");
break;
}
default: {
TINT_ICE(Transform, ctx.dst->Diagnostics())
<< "unhandled module-scope address space (" << sc << ")";
}
}
// Use a pointer for non-handle types.
utils::Vector<const ast::Attribute*, 2> attributes;
if (!ty->is_handle()) {
param_type = ctx.dst->ty.pointer(param_type, sc, var_ast->declared_access);
is_pointer = true;
// Disable validation of the parameter's address space and of arguments passed to it.
attributes.Push(ctx.dst->Disable(ast::DisabledValidation::kIgnoreAddressSpace));
attributes.Push(
ctx.dst->Disable(ast::DisabledValidation::kIgnoreInvalidPointerArgument));
}
// Redeclare the variable as a parameter.
ctx.InsertBack(func->params,
ctx.dst->Param(new_var_symbol, param_type, std::move(attributes)));
}
/// Replace all uses of `var` in `func` with references to `new_var`.
/// @param func the function
/// @param var the variable to replace
/// @param new_var the symbol to use for replacement
/// @param is_pointer true if `new_var` is a pointer to the new variable
/// @param is_wrapped true if `new_var` is an array wrapped in a structure
void ReplaceUsesInFunction(const ast::Function* func,
const sem::Variable* var,
Symbol new_var,
bool is_pointer,
bool is_wrapped) {
for (auto* user : var->Users()) {
if (user->Stmt()->Function()->Declaration() == func) {
const ast::Expression* expr = ctx.dst->Expr(new_var);
if (is_pointer) {
// If this identifier is used by an address-of operator, just remove the
// address-of instead of adding a deref, since we already have a pointer.
auto* ident = user->Declaration()->As<ast::IdentifierExpression>();
if (ident_to_address_of_.count(ident)) {
ctx.Replace(ident_to_address_of_[ident], expr);
continue;
}
expr = ctx.dst->Deref(expr);
}
if (is_wrapped) {
// Get the member from the wrapper structure.
expr = ctx.dst->MemberAccessor(expr, kWrappedArrayMemberName);
}
ctx.Replace(user->Declaration(), expr);
}
}
}
/// Process the module.
void Process() {
// Predetermine the list of function calls that need to be replaced.
using CallList = utils::Vector<const ast::CallExpression*, 8>;
std::unordered_map<const ast::Function*, CallList> calls_to_replace;
utils::Vector<const ast::Function*, 8> functions_to_process;
// Build a list of functions that transitively reference any module-scope variables.
for (auto* decl : ctx.src->Sem().Module()->DependencyOrderedDeclarations()) {
auto* func_ast = decl->As<ast::Function>();
if (!func_ast) {
continue;
}
auto* func_sem = ctx.src->Sem().Get(func_ast);
bool needs_processing = false;
for (auto* var : func_sem->TransitivelyReferencedGlobals()) {
if (var->AddressSpace() != ast::AddressSpace::kNone) {
needs_processing = true;
break;
}
}
if (needs_processing) {
functions_to_process.Push(func_ast);
// Find all of the calls to this function that will need to be replaced.
for (auto* call : func_sem->CallSites()) {
calls_to_replace[call->Stmt()->Function()->Declaration()].Push(
call->Declaration());
}
}
}
// Build a list of `&ident` expressions. We'll use this later to avoid generating
// expressions of the form `&*ident`, which break WGSL validation rules when this expression
// is passed to a function.
// TODO(jrprice): We should add support for bidirectional SEM tree traversal so that we can
// do this on the fly instead.
for (auto* node : ctx.src->ASTNodes().Objects()) {
auto* address_of = node->As<ast::UnaryOpExpression>();
if (!address_of || address_of->op != ast::UnaryOp::kAddressOf) {
continue;
}
if (auto* ident = address_of->expr->As<ast::IdentifierExpression>()) {
ident_to_address_of_[ident] = address_of;
}
}
for (auto* func_ast : functions_to_process) {
auto* func_sem = ctx.src->Sem().Get(func_ast);
bool is_entry_point = func_ast->IsEntryPoint();
bool needs_pointer_aliasing = false;
// Map module-scope variables onto their replacement.
struct NewVar {
Symbol symbol;
bool is_pointer;
bool is_wrapped;
};
std::unordered_map<const sem::Variable*, NewVar> var_to_newvar;
// We aggregate all workgroup variables into a struct to avoid hitting MSL's limit for
// threadgroup memory arguments.
Symbol workgroup_parameter_symbol;
WorkgroupParameterMemberList workgroup_parameter_members;
auto workgroup_param = [&]() {
if (!workgroup_parameter_symbol.IsValid()) {
workgroup_parameter_symbol = ctx.dst->Sym();
}
return workgroup_parameter_symbol;
};
// Process and redeclare all variables referenced by the function.
for (auto* var : func_sem->TransitivelyReferencedGlobals()) {
if (var->AddressSpace() == ast::AddressSpace::kNone) {
continue;
}
if (local_private_vars_.count(var)) {
continue;
}
// This is the symbol for the variable that replaces the module-scope var.
auto new_var_symbol = ctx.dst->Sym();
// Track whether the new variable is a pointer or not.
bool is_pointer = false;
// Track whether the new variable was wrapped in a struct or not.
bool is_wrapped = false;
// Check if this is a private variable that is only referenced by this function.
bool local_private = false;
if (var->AddressSpace() == ast::AddressSpace::kPrivate) {
local_private = true;
for (auto* user : var->Users()) {
auto* stmt = user->Stmt();
if (!stmt || stmt->Function() != func_sem) {
local_private = false;
break;
}
}
}
if (local_private) {
// Redeclare the variable at function scope.
auto* disable_validation =
ctx.dst->Disable(ast::DisabledValidation::kIgnoreAddressSpace);
auto* initializer = ctx.Clone(var->Declaration()->initializer);
auto* local_var = ctx.dst->Var(new_var_symbol,
CreateASTTypeFor(ctx, var->Type()->UnwrapRef()),
ast::AddressSpace::kPrivate, initializer,
utils::Vector{disable_validation});
ctx.InsertFront(func_ast->body->statements, ctx.dst->Decl(local_var));
local_private_vars_.insert(var);
} else {
// Process the variable to redeclare it as a parameter or local variable.
if (is_entry_point) {
ProcessVariableInEntryPoint(func_ast, var, new_var_symbol, workgroup_param,
workgroup_parameter_members, is_pointer,
is_wrapped);
} else {
ProcessVariableInUserFunction(func_ast, var, new_var_symbol, is_pointer);
if (var->AddressSpace() == ast::AddressSpace::kWorkgroup) {
needs_pointer_aliasing = true;
}
}
// Record the replacement symbol.
var_to_newvar[var] = {new_var_symbol, is_pointer, is_wrapped};
}
// Replace all uses of the module-scope variable.
ReplaceUsesInFunction(func_ast, var, new_var_symbol, is_pointer, is_wrapped);
}
// Allow pointer aliasing if needed.
if (needs_pointer_aliasing) {
ctx.InsertBack(func_ast->attributes,
ctx.dst->Disable(ast::DisabledValidation::kIgnorePointerAliasing));
}
if (!workgroup_parameter_members.IsEmpty()) {
// Create the workgroup memory parameter.
// The parameter is a struct that contains members for each workgroup variable.
auto* str =
ctx.dst->Structure(ctx.dst->Sym(), std::move(workgroup_parameter_members));
auto* param_type =
ctx.dst->ty.pointer(ctx.dst->ty.Of(str), ast::AddressSpace::kWorkgroup);
auto* param = ctx.dst->Param(
workgroup_param(), param_type,
utils::Vector{
ctx.dst->Disable(ast::DisabledValidation::kEntryPointParameter),
ctx.dst->Disable(ast::DisabledValidation::kIgnoreAddressSpace),
});
ctx.InsertFront(func_ast->params, param);
}
// Pass the variables as pointers to any functions that need them.
for (auto* call : calls_to_replace[func_ast]) {
auto* target = ctx.src->AST().Functions().Find(call->target.name->symbol);
auto* target_sem = ctx.src->Sem().Get(target);
// Add new arguments for any variables that are needed by the callee.
// For entry points, pass non-handle types as pointers.
for (auto* target_var : target_sem->TransitivelyReferencedGlobals()) {
auto sc = target_var->AddressSpace();
if (sc == ast::AddressSpace::kNone) {
continue;
}
auto it = var_to_newvar.find(target_var);
if (it == var_to_newvar.end()) {
// No replacement was created for this function.
continue;
}
auto new_var = it->second;
bool is_handle = target_var->Type()->UnwrapRef()->is_handle();
const ast::Expression* arg = ctx.dst->Expr(new_var.symbol);
if (new_var.is_wrapped) {
// The variable is wrapped in a struct, so we need to pass a pointer to the
// struct member instead.
arg = ctx.dst->AddressOf(
ctx.dst->MemberAccessor(ctx.dst->Deref(arg), kWrappedArrayMemberName));
} else if (is_entry_point && !is_handle && !new_var.is_pointer) {
// We need to pass a pointer and we don't already have one, so take
// the address of the new variable.
arg = ctx.dst->AddressOf(arg);
}
ctx.InsertBack(call->args, arg);
}
}
}
// Now remove all module-scope variables with these address spacees.
for (auto* var_ast : ctx.src->AST().GlobalVariables()) {
auto* var_sem = ctx.src->Sem().Get(var_ast);
if (var_sem->AddressSpace() != ast::AddressSpace::kNone) {
ctx.Remove(ctx.src->AST().GlobalDeclarations(), var_ast);
}
}
}
private:
// The structures that have already been cloned by this transform.
std::unordered_set<const sem::Struct*> cloned_structs_;
// Set of a private variables that are local to a single function.
std::unordered_set<const sem::Variable*> local_private_vars_;
// Map from identifier expression to the address-of expression that uses it.
std::unordered_map<const ast::IdentifierExpression*, const ast::UnaryOpExpression*>
ident_to_address_of_;
};
ModuleScopeVarToEntryPointParam::ModuleScopeVarToEntryPointParam() = default;
ModuleScopeVarToEntryPointParam::~ModuleScopeVarToEntryPointParam() = default;
Transform::ApplyResult ModuleScopeVarToEntryPointParam::Apply(const Program* src,
const DataMap&,
DataMap&) const {
if (!ShouldRun(src)) {
return SkipTransform;
}
ProgramBuilder b;
CloneContext ctx{&b, src, /* auto_clone_symbols */ true};
State state{ctx};
state.Process();
ctx.Clone();
return Program(std::move(b));
}
} // namespace tint::transform