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#include "src/tint/lang/core/ir/transform/common/referenced_module_vars.h"

#include "src/tint/lang/core/ir/control_instruction.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/user_call.h"
#include "src/tint/lang/core/ir/var.h"
#include "src/tint/utils/rtti/switch.h"

namespace tint::core::ir {

const ReferencedModuleVars::VarSet& ReferencedModuleVars::TransitiveReferences(Function* func) {
    return transitive_references_.GetOrAdd(func, [&] {
        VarSet vars;
        GetTransitiveReferences(func->Block(), vars);
        return vars;
    });
}

/// Get the set of variables transitively referenced by @p block.
/// @param block the block
/// @param vars the set of transitively referenced variables to populate
void ReferencedModuleVars::GetTransitiveReferences(Block* block, VarSet& vars) {
    // Add directly referenced vars.
    if (auto itr = block_to_direct_vars_.Get(block)) {
        for (auto& var : *itr) {
            vars.Add(var);
        }
    }

    // Loop over instructions in the block to find indirectly referenced vars.
    for (auto* inst : *block) {
        tint::Switch(
            inst,
            [&](UserCall* call) {
                // Get variables referenced by a function called from this block.
                const auto& callee_vars = TransitiveReferences(call->Target());
                for (auto* var : callee_vars) {
                    vars.Add(var);
                }
            },
            [&](ControlInstruction* ctrl) {
                // Recurse into control instructions and gather their referenced vars.
                ctrl->ForeachBlock([&](Block* blk) { GetTransitiveReferences(blk, vars); });
            });
    }
}

}  // namespace tint::core::ir