src/tint/lang/msl/writer/raise/module_constant.cc

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#include "src/tint/lang/msl/writer/raise/module_constant.h"

#include "src/tint/lang/core/ir/builder.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/validator.h"
#include "src/tint/lang/core/type/array.h"

#include "src/tint/lang/core/type/struct.h"
#include "src/tint/utils/containers/hashmap.h"

namespace tint::msl::writer::raise {

namespace {

/// PIMPL state for the transform.
struct State {
    core::ir::Module& ir;
    const ModuleConstantConfig& config;
    core::ir::Builder b{ir};
    core::type::Manager& ty{ir.Types()};

    /// @returns true if @p type is or contains a f16 type
    bool ContainsF16Type(const core::type::Type* type) {
        if (type->Is<core::type::F16>()) {
            return true;
        }

        if (type->IsScalar()) {
            return false;
        }

        if (const auto* str = type->As<core::type::Struct>()) {
            for (auto* member : str->Members()) {
                if (ContainsF16Type(member->Type())) {
                    return true;
                }
            }
            return false;
        }

        return ContainsF16Type(type->DeepestElement());
    }

    void Process() {
        Hashmap<core::ir::Value*, core::ir::Value*, 16> object_to_var;
        for (auto* inst : ir.Instructions()) {
            auto* access = inst->As<core::ir::Access>();
            if (!access) {
                continue;
            }

            auto* source_object = access->Object();
            auto* curr_const = source_object->As<core::ir::Constant>();
            if (!curr_const) {
                continue;
            }

            // We only handle struct and array for now as this transform is about avoiding
            // construction cost.
            if (!curr_const->Type()->IsAnyOf<core::type::Array, core::type::Struct>()) {
                continue;
            }

            if (config.disable_module_constant_f16 && ContainsF16Type(curr_const->Type())) {
                continue;
            }

            // Declare a variable and copy the source object to it.
            auto* var = object_to_var.GetOrAdd(source_object, [&] {
                // If the source object is a constant we use a module-scope variable
                core::ir::Let* decl = b.Let(curr_const);
                ir.root_block->Append(decl);
                return decl->Result();
            });
            access->SetOperand(core::ir::Access::kObjectOperandOffset, var);
        }
    }
};

}  // namespace

Result<SuccessType> ModuleConstant(core::ir::Module& ir, const ModuleConstantConfig& config) {
    auto result = ValidateAndDumpIfNeeded(ir, "msl.ModuleConstant", kModuleConstantCapabilities);
    if (result != Success) {
        return result;
    }

    State{ir, config}.Process();

    return Success;
}

}  // namespace tint::msl::writer::raise