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#include "src/tint/lang/hlsl/writer/raise/promote_initializers.h"

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

using namespace tint::core::fluent_types;     // NOLINT
using namespace tint::core::number_suffixes;  // NOLINT

namespace tint::hlsl::writer::raise {

namespace {

/// PIMPL state for the transform.
struct State {
    /// The IR module.
    core::ir::Module& ir;

    /// The IR builder.
    core::ir::Builder b{ir};

    /// The type manager.
    core::type::Manager& ty{ir.Types()};

    /// Process the module.
    void Process() {
        for (auto* block : ir.blocks.Objects()) {
            // In the root block, all structs need to be split out, no nested structs
            bool is_root_block = block == ir.root_block;

            Process(block, is_root_block);
        }
    }

    struct ValueInfo {
        core::ir::Instruction* inst;
        core::ir::Value* val;
    };

    void Process(core::ir::Block* block, bool is_root_block) {
        Vector<ValueInfo, 4> worklist;
        Hashset<core::ir::Value*, 4> seen;

        for (auto* inst : *block) {
            if (inst->Is<core::ir::Let>()) {
                continue;
            }
            if (inst->Is<core::ir::Var>()) {
                if (is_root_block) {
                    // split root var if needed ...
                }
                continue;
            }

            for (auto* operand : inst->Operands()) {
                if (!operand || seen.Contains(operand) || !operand->Type() ||
                    !operand->Type()->IsAnyOf<core::type::Struct, core::type::Array>()) {
                    continue;
                }
                if (operand->IsAnyOf<core::ir::InstructionResult, core::ir::Constant>()) {
                    seen.Add(operand);
                    worklist.Push({inst, operand});
                }
            }
        }

        for (auto& item : worklist) {
            if (auto* res = As<core::ir::InstructionResult>(item.val)) {
                PutInLet(res);
            } else if (auto* val = As<core::ir::Constant>(item.val)) {
                PutInLet(item.inst, val);
            }
        }
    }

    core::ir::Let* MakeLet(core::ir::Value* value) {
        auto* let = b.Let(value->Type());
        value->ReplaceAllUsesWith(let->Result(0));
        let->SetValue(value);

        auto name = b.ir.NameOf(value);
        if (name.IsValid()) {
            b.ir.SetName(let->Result(0), name);
            b.ir.ClearName(value);
        }
        return let;
    }

    void PutInLet(core::ir::Instruction* inst, core::ir::Value* value) {
        auto* let = MakeLet(value);
        let->InsertBefore(inst);
    }

    void PutInLet(core::ir::InstructionResult* value) {
        auto* inst = value->Instruction();
        auto* let = MakeLet(value);
        let->InsertAfter(inst);
    }
};

}  // namespace

Result<SuccessType> PromoteInitializers(core::ir::Module& ir) {
    auto result = ValidateAndDumpIfNeeded(ir, "PromoteInitializers transform");
    if (result != Success) {
        return result;
    }

    State{ir}.Process();

    return Success;
}

}  // namespace tint::hlsl::writer::raise