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// Copyright 2022 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
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#include "src/tint/lang/spirv/reader/ast_lower/atomics.h"
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#include "src/tint/lang/core/fluent_types.h"
#include "src/tint/lang/core/type/reference.h"
#include "src/tint/lang/wgsl/program/clone_context.h"
#include "src/tint/lang/wgsl/program/program_builder.h"
#include "src/tint/lang/wgsl/resolver/resolve.h"
#include "src/tint/lang/wgsl/sem/block_statement.h"
#include "src/tint/lang/wgsl/sem/function.h"
#include "src/tint/lang/wgsl/sem/index_accessor_expression.h"
#include "src/tint/lang/wgsl/sem/load.h"
#include "src/tint/lang/wgsl/sem/member_accessor_expression.h"
#include "src/tint/lang/wgsl/sem/statement.h"
#include "src/tint/utils/containers/map.h"
#include "src/tint/utils/containers/unique_vector.h"
#include "src/tint/utils/rtti/switch.h"
using namespace tint::core::number_suffixes; // NOLINT
using namespace tint::core::fluent_types; // NOLINT
TINT_INSTANTIATE_TYPEINFO(tint::spirv::reader::Atomics);
TINT_INSTANTIATE_TYPEINFO(tint::spirv::reader::Atomics::Stub);
namespace tint::spirv::reader {
/// PIMPL state for the transform
struct Atomics::State {
private:
/// A struct that has been forked because a subset of members were made atomic.
struct ForkedStruct {
Symbol name;
std::unordered_set<size_t> atomic_members;
};
/// The source program
const Program& src;
/// The target program builder
ProgramBuilder b;
/// The clone context
program::CloneContext ctx = {&b, &src, /* auto_clone_symbols */ true};
std::unordered_map<const core::type::Struct*, ForkedStruct> forked_structs;
std::unordered_set<const sem::Variable*> atomic_variables;
UniqueVector<const sem::ValueExpression*, 8> atomic_expressions;
public:
/// Constructor
/// @param program the source program
explicit State(const Program& program) : src(program) {}
/// Runs the transform
/// @returns the new program or SkipTransform if the transform is not required
ApplyResult Run() {
bool made_changes = false;
// Look for stub functions generated by the SPIR-V reader, which are used as placeholders
// for atomic builtin calls.
for (auto* fn : ctx.src->AST().Functions()) {
if (auto* stub = ast::GetAttribute<Stub>(fn->attributes)) {
auto* sem = ctx.src->Sem().Get(fn);
for (auto* call : sem->CallSites()) {
// The first argument is always the atomic.
// The stub passes this by value, whereas the builtin wants a pointer.
// Take the address of the atomic argument.
auto& args = call->Declaration()->args;
auto out_args = ctx.Clone(args);
out_args[0] = b.AddressOf(out_args[0]);
// Replace all callsites of this stub to a call to the real builtin
if (stub->builtin == wgsl::BuiltinFn::kAtomicCompareExchangeWeak) {
// atomicCompareExchangeWeak returns a struct, so insert a call to it above
// the current statement, and replace the current call with the struct's
// `old_value` member.
auto* block = call->Stmt()->Block()->Declaration();
auto old_value = b.Symbols().New("old_value");
auto old_value_decl = b.Decl(b.Let(
old_value,
b.MemberAccessor(b.Call(wgsl::str(stub->builtin), std::move(out_args)),
"old_value")));
ctx.InsertBefore(block->statements, call->Stmt()->Declaration(),
old_value_decl);
ctx.Replace(call->Declaration(), b.Expr(old_value));
} else {
ctx.Replace(call->Declaration(),
b.Call(wgsl::str(stub->builtin), std::move(out_args)));
}
// Keep track of this expression. We'll need to modify the root identifier /
// structure to be atomic.
atomic_expressions.Add(ctx.src->Sem().GetVal(args[0]));
}
// Remove the stub from the output program
ctx.Remove(ctx.src->AST().GlobalDeclarations(), fn);
made_changes = true;
}
}
if (!made_changes) {
return SkipTransform;
}
// Transform all variables and structure members that were used in atomic operations as
// atomic types. This propagates up originating expression chains.
ProcessAtomicExpressions();
// If we need to change structure members, then fork them.
if (!forked_structs.empty()) {
ctx.ReplaceAll([&](const ast::Struct* str) {
// Is `str` a structure we need to fork?
auto* str_ty = ctx.src->Sem().Get(str);
if (auto it = forked_structs.find(str_ty); it != forked_structs.end()) {
const auto& forked = it->second;
// Re-create the structure swapping in the atomic-flavoured members
Vector<const ast::StructMember*, 8> members;
members.Reserve(str->members.Length());
for (size_t i = 0; i < str->members.Length(); i++) {
auto* member = str->members[i];
if (forked.atomic_members.count(i)) {
auto type = AtomicTypeFor(ctx.src->Sem().Get(member)->Type());
auto name = member->name->symbol.Name();
members.Push(b.Member(name, type, ctx.Clone(member->attributes)));
} else {
members.Push(ctx.Clone(member));
}
}
b.Structure(forked.name, std::move(members));
}
return nullptr;
});
}
// Replace assignments and decls from atomic variables with atomicLoads, and assignments to
// atomic variables with atomicStores.
ReplaceLoadsAndStores();
ctx.Clone();
return resolver::Resolve(b);
}
private:
ForkedStruct& Fork(const core::type::Struct* str) {
auto& forked = forked_structs[str];
if (!forked.name.IsValid()) {
forked.name = b.Symbols().New(str->Name().Name() + "_atomic");
}
return forked;
}
void ProcessAtomicExpressions() {
for (size_t i = 0; i < atomic_expressions.Length(); i++) {
Switch(
atomic_expressions[i]->UnwrapLoad(), //
[&](const sem::VariableUser* user) {
auto* v = user->Variable()->Declaration();
if (v->type && atomic_variables.emplace(user->Variable()).second) {
ctx.Replace(v->type.expr, b.Expr(AtomicTypeFor(user->Variable()->Type())));
}
if (auto* ctor = user->Variable()->Initializer()) {
atomic_expressions.Add(ctor);
}
},
[&](const sem::StructMemberAccess* access) {
// Fork the struct (the first time) and mark member(s) that need to be made
// atomic.
auto* member = access->Member();
Fork(member->Struct()).atomic_members.emplace(member->Index());
atomic_expressions.Add(access->Object());
},
[&](const sem::IndexAccessorExpression* index) {
atomic_expressions.Add(index->Object());
},
[&](const sem::ValueExpression* e) {
if (auto* unary = e->Declaration()->As<ast::UnaryOpExpression>()) {
atomic_expressions.Add(ctx.src->Sem().GetVal(unary->expr));
}
});
}
}
ast::Type AtomicTypeFor(const core::type::Type* ty) {
return Switch(
ty, //
[&](const core::type::I32*) { return b.ty.atomic(CreateASTTypeFor(ctx, ty)); },
[&](const core::type::U32*) { return b.ty.atomic(CreateASTTypeFor(ctx, ty)); },
[&](const core::type::Struct* str) { return b.ty(Fork(str).name); },
[&](const core::type::Array* arr) {
if (arr->Count()->Is<core::type::RuntimeArrayCount>()) {
return b.ty.array(AtomicTypeFor(arr->ElemType()));
}
auto count = arr->ConstantCount();
if (!count) {
ctx.dst->Diagnostics().AddError(Source{})
<< "the Atomics transform does not currently support array counts that use "
"override values";
count = 1;
}
return b.ty.array(AtomicTypeFor(arr->ElemType()), u32(count.value()));
},
[&](const core::type::Pointer* ptr) {
return b.ty.ptr(ptr->AddressSpace(), AtomicTypeFor(ptr->StoreType()),
ptr->Access());
},
[&](const core::type::Reference* ref) { return AtomicTypeFor(ref->StoreType()); }, //
TINT_ICE_ON_NO_MATCH);
}
void ReplaceLoadsAndStores() {
// Returns true if 'e' is a reference to an atomic variable or struct member
auto is_ref_to_atomic_var = [&](const sem::ValueExpression* e) {
if (tint::Is<core::type::Reference>(e->Type()) && e->RootIdentifier() &&
(atomic_variables.count(e->RootIdentifier()) != 0)) {
// If it's a struct member, make sure it's one we marked as atomic
if (auto* ma = e->As<sem::StructMemberAccess>()) {
auto it = forked_structs.find(ma->Member()->Struct());
if (it != forked_structs.end()) {
auto& forked = it->second;
return forked.atomic_members.count(ma->Member()->Index()) != 0;
}
}
return true;
}
return false;
};
// Look for loads and stores of atomic variables we've collected so far, and replace them
// with atomicLoad and atomicStore.
for (auto* node : ctx.src->ASTNodes().Objects()) {
if (auto* load = ctx.src->Sem().Get<sem::Load>(node)) {
if (is_ref_to_atomic_var(load->Reference())) {
ctx.Replace(load->Reference()->Declaration(), [=] {
auto* expr = ctx.CloneWithoutTransform(load->Reference()->Declaration());
return b.Call(wgsl::BuiltinFn::kAtomicLoad, b.AddressOf(expr));
});
}
} else if (auto* assign = node->As<ast::AssignmentStatement>()) {
auto* sem_lhs = ctx.src->Sem().GetVal(assign->lhs);
if (is_ref_to_atomic_var(sem_lhs)) {
ctx.Replace(assign, [=] {
auto* lhs = ctx.CloneWithoutTransform(assign->lhs);
auto* rhs = ctx.CloneWithoutTransform(assign->rhs);
auto* call = b.Call(wgsl::BuiltinFn::kAtomicStore, b.AddressOf(lhs), rhs);
return b.CallStmt(call);
});
}
}
}
}
};
Atomics::Atomics() = default;
Atomics::~Atomics() = default;
Atomics::Stub::Stub(GenerationID pid, ast::NodeID nid, wgsl::BuiltinFn b)
: Base(pid, nid, tint::Empty), builtin(b) {}
Atomics::Stub::~Stub() = default;
std::string Atomics::Stub::InternalName() const {
return "@internal(spirv-atomic " + std::string(wgsl::str(builtin)) + ")";
}
const Atomics::Stub* Atomics::Stub::Clone(ast::CloneContext& ctx) const {
return ctx.dst->ASTNodes().Create<Atomics::Stub>(ctx.dst->ID(), ctx.dst->AllocateNodeID(),
builtin);
}
ast::transform::Transform::ApplyResult Atomics::Apply(const Program& src,
const ast::transform::DataMap&,
ast::transform::DataMap&) const {
return State{src}.Run();
}
} // namespace tint::spirv::reader