2015-03-24 21:31:36 +00:00
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Driver
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======
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2017-04-16 16:03:39 +00:00
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Note: this document discuss Mach-O port of LLD. For ELF and COFF,
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see :doc:`index`.
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2015-03-24 21:31:36 +00:00
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.. contents::
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:local:
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Introduction
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============
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This document describes the lld driver. The purpose of this document is to
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describe both the motivation and design goals for the driver, as well as details
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of the internal implementation.
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Overview
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========
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The lld driver is designed to support a number of different command line
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interfaces. The main interfaces we plan to support are binutils' ld, Apple's
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ld, and Microsoft's link.exe.
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Flavors
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-------
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Each of these different interfaces is referred to as a flavor. There is also an
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extra flavor "core" which is used to exercise the core functionality of the
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linker it the test suite.
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* gnu
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* darwin
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* link
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* core
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Selecting a Flavor
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^^^^^^^^^^^^^^^^^^
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There are two different ways to tell lld which flavor to be. They are checked in
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order, so the second overrides the first. The first is to symlink :program:`lld`
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as :program:`lld-{flavor}` or just :program:`{flavor}`. You can also specify
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it as the first command line argument using ``-flavor``::
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$ lld -flavor gnu
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There is a shortcut for ``-flavor core`` as ``-core``.
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Adding an Option to an existing Flavor
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======================================
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#. Add the option to the desired :file:`lib/Driver/{flavor}Options.td`.
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#. Add to :cpp:class:`lld::FlavorLinkingContext` a getter and setter method
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for the option.
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#. Modify :cpp:func:`lld::FlavorDriver::parse` in :file:
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`lib/Driver/{Flavor}Driver.cpp` to call the targetInfo setter
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for corresponding to the option.
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#. Modify {Flavor}Reader and {Flavor}Writer to use the new targtInfo option.
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Adding a Flavor
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===============
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#. Add an entry for the flavor in :file:`include/lld/Driver/Driver.h` to
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:cpp:class:`lld::UniversalDriver::Flavor`.
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#. Add an entry in :file:`lib/Driver/UniversalDriver.cpp` to
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:cpp:func:`lld::Driver::strToFlavor` and
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:cpp:func:`lld::UniversalDriver::link`.
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2017-01-02 19:19:15 +00:00
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This allows the flavor to be selected via symlink and `-flavor`.
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2015-03-24 21:31:36 +00:00
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#. Add a tablegen file called :file:`lib/Driver/{flavor}Options.td` that
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describes the options. If the options are a superset of another driver, that
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driver's td file can simply be included. The :file:`{flavor}Options.td` file
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must also be added to :file:`lib/Driver/CMakeLists.txt`.
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#. Add a ``{flavor}Driver`` as a subclass of :cpp:class:`lld::Driver`
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in :file:`lib/Driver/{flavor}Driver.cpp`.
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