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package com.oracle.truffle.llvm.runtime.nodes.others;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.dsl.CachedContext;
import com.oracle.truffle.api.dsl.Specialization;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.llvm.runtime.LLVMAlias;
import com.oracle.truffle.llvm.runtime.LLVMContext;
import com.oracle.truffle.llvm.runtime.LLVMLanguage;
import com.oracle.truffle.llvm.runtime.LLVMSymbol;
import com.oracle.truffle.llvm.runtime.except.LLVMLinkerException;
import com.oracle.truffle.llvm.runtime.memory.LLVMStack;
import com.oracle.truffle.llvm.runtime.memory.LLVMStack.LLVMStackAccess;
import com.oracle.truffle.llvm.runtime.nodes.api.LLVMExpressionNode;
import com.oracle.truffle.llvm.runtime.nodes.func.LLVMRootNode;
import com.oracle.truffle.llvm.runtime.pointer.LLVMPointer;

Returns the value of a given symbol for the current context. This node behaves differently for single context and multi context mode: In single context mode, the cached context will resolve to a constant, which is very efficient, but in multi context mode, it's more efficient to get the context from the LLVMStack stored in the frame. /**
 * Returns the value of a given symbol for the current context. This node behaves differently for
 * single context and multi context mode: In single context mode, the cached context will resolve to
 * a constant, which is very efficient, but in multi context mode, it's more efficient to get the
 * context from the {@link LLVMStack} stored in the frame.
 */
public abstract class LLVMAccessSymbolNode extends LLVMExpressionNode {

    protected final LLVMSymbol symbol;

    @CompilationFinal private LLVMStackAccess stackAccess;

    LLVMAccessSymbolNode(LLVMSymbol symbol) {
        this.symbol = LLVMAlias.resolveAlias(symbol);
    }

    @Override
    public abstract LLVMPointer executeGeneric(VirtualFrame frame);

    @Override
    public String toString() {
        return getShortString("symbol");
    }

    public LLVMSymbol getSymbol() {
        return symbol;
    }

    private LLVMPointer checkNull(LLVMPointer result) {
        if (result == null) {
            CompilerDirectives.transferToInterpreter();
            throw new LLVMLinkerException(this, String.format("External %s %s cannot be found.", symbol.getKind(), symbol.getName()));
        }
        return result;
    }

    /*
     * CachedContext is very efficient in single-context mode, otherwise we should get the context
     * from the frame.
     */
    @Specialization(assumptions = "singleContextAssumption()")
    public LLVMPointer accessSingleContext(
                    @CachedContext(LLVMLanguage.class) LLVMContext context) {
        return checkNull(context.getSymbol(symbol));
    }

    @Specialization
    public LLVMPointer accessMultiContext(VirtualFrame frame) {
        if (stackAccess == null) {
            CompilerDirectives.transferToInterpreterAndInvalidate();
            stackAccess = ((LLVMRootNode) getRootNode()).getStackAccess();
        }
        return checkNull(stackAccess.executeGetStack(frame).getContext().getSymbol(symbol));
    }
}