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003f93f134
As Ben pointed out, GAS doesn't support this syntax so we should give at least some warning that it might not be portable. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188377 91177308-0d34-0410-b5e6-96231b3b80d8
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2.4 KiB
ReStructuredText
107 lines
2.4 KiB
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===============
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LLVM Extensions
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===============
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.. contents::
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:local:
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.. toctree::
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:hidden:
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Introduction
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============
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This document describes extensions to tools and formats LLVM seeks compatibility
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with.
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General Assembly Syntax
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===========================
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C99-style Hexadecimal Floating-point Constants
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----------------------------------------------
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LLVM's assemblers allow floating-point constants to be written in C99's
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hexadecimal format instead of decimal if desired.
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.. code-block:: gas
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.section .data
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.float 0x1c2.2ap3
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Machine-specific Assembly Syntax
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================================
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X86/COFF-Dependent
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------------------
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Relocations
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^^^^^^^^^^^
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The following additional relocation type is supported:
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**@IMGREL** (AT&T syntax only) generates an image-relative relocation that
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corresponds to the COFF relocation types ``IMAGE_REL_I386_DIR32NB`` (32-bit) or
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``IMAGE_REL_AMD64_ADDR32NB`` (64-bit).
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.. code-block:: gas
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.text
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fun:
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mov foo@IMGREL(%ebx, %ecx, 4), %eax
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.section .pdata
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.long fun@IMGREL
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.long (fun@imgrel + 0x3F)
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.long $unwind$fun@imgrel
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``.linkonce`` Directive
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax:
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``.linkonce [ comdat type [ section identifier ] ]``
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Supported COMDAT types:
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``discard``
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Discards duplicate sections with the same COMDAT symbol. This is the default
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if no type is specified.
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``one_only``
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If the symbol is defined multiple times, the linker issues an error.
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``same_size``
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Duplicates are discarded, but the linker issues an error if any have
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different sizes.
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``same_contents``
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Duplicates are discarded, but the linker issues an error if any duplicates
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do not have exactly the same content.
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``associative``
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Links the section if a certain other COMDAT section is linked. This other
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section is indicated by its section identifier following the comdat type.
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The following restrictions apply to the associated section:
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1. It must be the name of a section already defined.
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2. It must differ from the current section.
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3. It must be a COMDAT section.
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4. It cannot be another associative COMDAT section.
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``largest``
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Links the largest section from among the duplicates.
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``newest``
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Links the newest section from among the duplicates.
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.. code-block:: gas
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.section .text$foo
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.linkonce
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...
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.section .xdata$foo
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.linkonce associative .text$foo
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...
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