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package com.oracle.truffle.llvm.initialization;

import java.util.ArrayList;

import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.llvm.initialization.AllocExternalSymbolNodeFactory.AllocExistingLocalSymbolsNodeGen;
import com.oracle.truffle.llvm.initialization.AllocExternalSymbolNodeFactory.AllocExistingLocalSymbolsNodeGen.AllocExistingGlobalSymbolsNodeGen.AllocExternalGlobalNodeGen;
import com.oracle.truffle.llvm.parser.LLVMParserResult;
import com.oracle.truffle.llvm.parser.model.GlobalSymbol;
import com.oracle.truffle.llvm.parser.model.functions.FunctionSymbol;
import com.oracle.truffle.llvm.runtime.LLVMContext;
import com.oracle.truffle.llvm.runtime.LLVMFunction;
import com.oracle.truffle.llvm.runtime.LLVMLocalScope;
import com.oracle.truffle.llvm.runtime.LLVMScope;
import com.oracle.truffle.llvm.runtime.LLVMSymbol;
import com.oracle.truffle.llvm.runtime.global.LLVMGlobal;
import com.oracle.truffle.llvm.runtime.nodes.api.LLVMNode;
import com.oracle.truffle.llvm.runtime.pointer.LLVMPointer;

The aim of InitializeOverwriteNode is to identify which defined symbols will be resolved to their corresponding symbol in the local scope when they are called. If they resolve to the symbol in the local scope then this symbol from the local scope is place into this defined symbol's location in the symbol table. This means the local and global scope is no longer required for symbol resolution, and everything is done simply by looking up the symbol in the file scope. Overwriting for defined symbols that will be resolved to the local scope instead of the file scope. If a defined symbol is required to be access via the local scope instead of it's file scope, then that symbol's entry in the symbol table will be that of the defined symbol from the local scope. 
See Also:
InitializeScopeNode
InitializeSymbolsNode
InitializeGlobalNode
InitializeModuleNode
InitializeExternalNode/**
 *
 * The aim of {@link InitializeOverwriteNode} is to identify which defined symbols will be resolved
 * to their corresponding symbol in the local scope when they are called. If they resolve to the
 * symbol in the local scope then this symbol from the local scope is place into this defined
 * symbol's location in the symbol table. This means the local and global scope is no longer
 * required for symbol resolution, and everything is done simply by looking up the symbol in the
 * file scope.
 *
 * Overwriting for defined symbols that will be resolved to the local scope instead of the file
 * scope. If a defined symbol is required to be access via the local scope instead of it's file
 * scope, then that symbol's entry in the symbol table will be that of the defined symbol from the
 * local scope.
 *
 * @see InitializeScopeNode
 * @see InitializeSymbolsNode
 * @see InitializeGlobalNode
 * @see InitializeModuleNode
 * @see InitializeExternalNode
 */
public final class InitializeOverwriteNode extends LLVMNode {

    @Children private final AllocExternalSymbolNode[] allocExternalSymbols;
    @CompilationFinal(dimensions = 1) private final LLVMSymbol[] symbols;

    public InitializeOverwriteNode(LLVMParserResult result) {
        ArrayList<LLVMSymbol> symbolsList = new ArrayList<>();
        ArrayList<AllocExternalSymbolNode> allocExternaSymbolsList = new ArrayList<>();
        LLVMScope fileScope = result.getRuntime().getFileScope();

        // Rewrite all overridable functions and globals in the filescope from their respective
        // function/global in the localscope.
        for (FunctionSymbol symbol : result.getDefinedFunctions()) {
            if (symbol.isOverridable()) {
                LLVMFunction function = fileScope.getFunction(symbol.getName());
                // Functions are overwritten by functions from the localScope
                symbolsList.add(function);
                allocExternaSymbolsList.add(AllocExistingLocalSymbolsNodeGen.create(function));
            }
        }
        for (GlobalSymbol symbol : result.getDefinedGlobals()) {
            // Cannot override the reserved symbols CONSTRUCTORS_VARNAME and
            // DECONSTRUCTORS_VARNAME
            if (symbol.isOverridable() && !symbol.isIntrinsicGlobalVariable()) {
                LLVMGlobal global = fileScope.getGlobalVariable(symbol.getName());
                // Globals are overwritten by (non-hidden) global symbol of the same name in the
                // globalscope
                symbolsList.add(global);
                allocExternaSymbolsList.add(AllocExternalGlobalNodeGen.create(global));
            }
        }
        this.symbols = symbolsList.toArray(LLVMSymbol.EMPTY);
        this.allocExternalSymbols = allocExternaSymbolsList.toArray(AllocExternalSymbolNode.EMPTY);
    }

    public void execute(LLVMContext context, LLVMLocalScope localScope) {
        LLVMScope globalScope = context.getGlobalScope();
        for (int i = 0; i < allocExternalSymbols.length; i++) {
            AllocExternalSymbolNode allocSymbol = allocExternalSymbols[i];
            LLVMPointer pointer = allocSymbol.execute(localScope, globalScope, null, null, context);
            // skip allocating fallbacks
            if (pointer == null) {
                continue;
            }
            context.initializeSymbol(symbols[i], pointer);
        }
    }
}