src/tint/lang/glsl/writer/writer.cc

// Copyright 2021 The Dawn & Tint Authors
//
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#include "src/tint/lang/glsl/writer/writer.h"

#include "src/tint/lang/core/ir/core_builtin_call.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/referenced_module_vars.h"
#include "src/tint/lang/core/ir/validator.h"
#include "src/tint/lang/core/ir/var.h"
#include "src/tint/lang/core/type/binding_array.h"
#include "src/tint/lang/core/type/pointer.h"
#include "src/tint/lang/core/type/storage_texture.h"
#include "src/tint/lang/core/type/texel_buffer.h"
#include "src/tint/lang/core/type/u16.h"
#include "src/tint/lang/glsl/writer/common/option_helpers.h"
#include "src/tint/lang/glsl/writer/printer/printer.h"
#include "src/tint/lang/glsl/writer/raise/raise.h"

namespace tint::glsl::writer {

namespace {

Result<SuccessType> CanGenerate(const core::ir::Module& ir, const Options& options) {
    // Check for unsupported types.
    for (auto* ty : ir.Types()) {
        if (ty->Is<core::type::SubgroupMatrix>()) {
            return Failure("subgroup matrices are not supported by the GLSL backend");
        }
        if (ty->Is<core::type::TexelBuffer>()) {
            // TODO(crbug/382544164): Prototype texel buffer feature
            return Failure("texel buffers are not supported by the GLSL backend");
        }
        if (auto* ba = ty->As<core::type::BindingArray>()) {
            if (ba->Count()->Is<core::type::RuntimeArrayCount>()) {
                return Failure("runtime binding array not supported by the GLSL backend");
            }

            // TODO(464058128): Add support for binding_array<texture_1d<*>, N> in the
            // TexturePolyfill transform.
            auto* tex = ba->ElemType()->As<core::type::Texture>();
            if (tex && tex->Dim() == core::type::TextureDimension::k1d) {
                return Failure(
                    "1D textures inside binding arrays are not yet supported by the GLSL backend");
            }
        }
        if (ty->Is<core::type::Buffer>()) {
            return Failure("buffers are not supported by the GLSL backend");
        }
        if (ty->Is<core::type::U16>()) {
            return Failure("16-bit unsigned integers are not supported by the GLSL backend");
        }
    }

    core::ir::Function* ep_func = nullptr;
    for (auto* f : ir.functions) {
        if (!f->IsEntryPoint()) {
            continue;
        }
        if (f->SubgroupSize().has_value()) {
            return Failure("subgroups are not supported by the GLSL backend");
        }
        if (ir.NameOf(f).NameView() == options.entry_point_name) {
            ep_func = f;
            break;
        }
    }

    // No entrypoint, so no bindings needed
    if (!ep_func) {
        return Failure("entry point not found");
    }

    // Make sure that every texture variable is in the texture_builtins_from_uniform binding list,
    // otherwise TextureBuiltinsFromUniform will fail.
    // TODO(https://issues.chromium.org/427172887) Be more precise for the
    // texture_builtins_from_uniform checks. Also ensure there is at most one user-declared
    // immediate.
    core::ir::ReferencedModuleVars<const core::ir::Module> referenced_module_vars{ir};
    auto& refs = referenced_module_vars.TransitiveReferences(ep_func);

    Vector<tint::BindingPoint, 4> ext_tex_bps;
    for (auto* var : refs) {
        auto* ptr = var->Result()->Type()->As<core::type::Pointer>();

        // The pixel_local extension is not supported by the GLSL backend.
        if (ptr->AddressSpace() == core::AddressSpace::kPixelLocal) {
            return Failure("pixel_local address space is not supported by the GLSL backend");
        }

        if (ptr->AddressSpace() == core::AddressSpace::kHandle) {
            const core::type::Type* handle_type = ptr->StoreType();

            // Check texel formats for read-write storage textures when targeting ES.
            if (options.version.IsES()) {
                if (auto* st = handle_type->As<core::type::StorageTexture>()) {
                    if (st->Access() == core::Access::kReadWrite) {
                        switch (st->TexelFormat()) {
                            case core::TexelFormat::kR32Float:
                            case core::TexelFormat::kR32Sint:
                            case core::TexelFormat::kR32Uint:
                                break;
                            default:
                                return Failure("unsupported read-write storage texture format");
                        }
                    }
                }
            }
        }
    }

    // Check for calls to unsupported builtin functions.
    for (auto* inst : ir.Instructions()) {
        auto* call = inst->As<core::ir::CoreBuiltinCall>();
        if (!call) {
            continue;
        }

        if (core::IsSubgroup(call->Func())) {
            return Failure("subgroups are not supported by the GLSL backend");
        }
        if (call->Func() == core::BuiltinFn::kInputAttachmentLoad) {
            return Failure("input attachments are not supported by the GLSL backend");
        }
        if (call->Func() == core::BuiltinFn::kGetResource ||
            call->Func() == core::BuiltinFn::kHasResource) {
            return Failure("resource tables not supported by the GLSL backend");
        }
        if (call->Func() == core::BuiltinFn::kPrint) {
            return Failure("print is not supported by the GLSL backend");
        }
        if (call->Func() == core::BuiltinFn::kAtomicStoreMax ||
            call->Func() == core::BuiltinFn::kAtomicStoreMin) {
            return Failure(
                "64-bit (vec2u) atomic operations are not yet supported by the GLSL backend");
        }
    }

    // Check for unsupported shader IO builtins.
    auto check_io_attributes = [&](const core::IOAttributes& attributes) -> Result<SuccessType> {
        if (attributes.builtin == core::BuiltinValue::kSubgroupId ||
            attributes.builtin == core::BuiltinValue::kSubgroupInvocationId ||
            attributes.builtin == core::BuiltinValue::kSubgroupSize ||
            attributes.builtin == core::BuiltinValue::kNumSubgroups) {
            return Failure("subgroups are not supported by the GLSL backend");
        }
        if (attributes.builtin == core::BuiltinValue::kClipDistances) {
            return Failure("clip_distances is not supported by the GLSL backend");
        }
        if (attributes.builtin == core::BuiltinValue::kCullDistance) {
            return Failure("cull_distance is not supported by the GLSL backend");
        }
        if (attributes.color.has_value()) {
            return Failure("@color attribute is not supported by the GLSL backend");
        }
        return Success;
    };
    // Check input attributes.
    for (auto* param : ep_func->Params()) {
        if (auto* str = param->Type()->As<core::type::Struct>()) {
            for (auto* member : str->Members()) {
                TINT_CHECK_RESULT(check_io_attributes(member->Attributes()));
            }
        } else {
            TINT_CHECK_RESULT(check_io_attributes(param->Attributes()));
        }
    }
    // Check output attributes.
    if (auto* str = ep_func->ReturnType()->As<core::type::Struct>()) {
        for (auto* member : str->Members()) {
            TINT_CHECK_RESULT(check_io_attributes(member->Attributes()));
        }
    } else {
        TINT_CHECK_RESULT(check_io_attributes(ep_func->ReturnAttributes()));
    }

    TINT_CHECK_RESULT(ValidateBindingOptions(options));

    return Success;
}

}  // namespace

Result<Output> Generate(core::ir::Module& ir, const Options& options) {
    TINT_CHECK_RESULT(CanGenerate(ir, options));

    // Raise from core-dialect to GLSL-dialect.
    TINT_CHECK_RESULT(Raise(ir, options));

    return Print(ir, options);
}

}  // namespace tint::glsl::writer