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llvm-mirror/docs/Extensions.rst
Nico Rieck 8e22855ea6 MC: Support COFF image-relative MCSymbolRefs
Add support for the COFF relocation types IMAGE_REL_I386_DIR32NB and
IMAGE_REL_AMD64_ADDR32NB for 32- and 64-bit respectively. These are
similar to normal 4-byte relocations except that they do not include
the base address of the image.

Image-relative relocations are used for debug information (32-bit) and
SEH unwind tables (64-bit).

A new MCSymbolRef variant called 'VK_COFF_IMGREL32' is introduced to
specify such relocations. For AT&T assembly, this variant can be accessed
using the symbol suffix '@imgrel'.

llvm-svn: 179240
2013-04-10 23:28:17 +00:00

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===============
LLVM Extensions
===============
.. contents::
:local:
:depth: 1
.. toctree::
:hidden:
Introduction
============
This document describes extensions to tools and formats LLVM seeks compatibility
with.
Machine-specific Assembly Syntax
================================
X86/COFF-Dependent
------------------
The following additional relocation type is supported:
**@IMGREL** (AT&T syntax only) generates an image-relative relocation that
corresponds to the COFF relocation types ``IMAGE_REL_I386_DIR32NB`` (32-bit) or
``IMAGE_REL_AMD64_ADDR32NB`` (64-bit).
.. code-block:: gas
.text
fun:
mov foo@IMGREL(%ebx, %ecx, 4), %eax
.section .pdata
.long fun@IMGREL
.long (fun@imgrel + 0x3F)
.long $unwind$fun@imgrel