final GeneratorAdapter mv = mv();
final int loc = localsOffset();
Label l_0 = new Label();
Label l_1 = new Label();
compile( _a );
mv.visitInsn( Opcodes.DUP2 );
mv.visitVarInsn( Opcodes.LSTORE, 0 + loc );
mv.visitInsn( Opcodes.LCONST_0 );
mv.visitInsn( Opcodes.LCMP );
mv.visitJumpInsn( Opcodes.IFGE, l_0 );
mv.visitVarInsn( Opcodes.LLOAD, 0 + loc );