87 lines
3.3 KiB
ReStructuredText
87 lines
3.3 KiB
ReStructuredText
=======================================
|
|
LLVM's Optional Rich Disassembly Output
|
|
=======================================
|
|
|
|
.. contents::
|
|
:local:
|
|
|
|
Introduction
|
|
============
|
|
|
|
LLVM's default disassembly output is raw text. To allow consumers more ability
|
|
to introspect the instructions' textual representation or to reformat for a more
|
|
user friendly display there is an optional rich disassembly output.
|
|
|
|
This optional output is sufficient to reference into individual portions of the
|
|
instruction text. This is intended for clients like disassemblers, list file
|
|
generators, and pretty-printers, which need more than the raw instructions and
|
|
the ability to print them.
|
|
|
|
To provide this functionality the assembly text is marked up with annotations.
|
|
The markup is simple enough in syntax to be robust even in the case of version
|
|
mismatches between consumers and producers. That is, the syntax generally does
|
|
not carry semantics beyond "this text has an annotation," so consumers can
|
|
simply ignore annotations they do not understand or do not care about.
|
|
|
|
After calling ``LLVMCreateDisasm()`` to create a disassembler context the
|
|
optional output is enable with this call:
|
|
|
|
.. code-block:: c
|
|
|
|
LLVMSetDisasmOptions(DC, LLVMDisassembler_Option_UseMarkup);
|
|
|
|
Then subsequent calls to ``LLVMDisasmInstruction()`` will return output strings
|
|
with the marked up annotations.
|
|
|
|
Instruction Annotations
|
|
=======================
|
|
|
|
.. _contextual markups:
|
|
|
|
Contextual markups
|
|
------------------
|
|
|
|
Annoated assembly display will supply contextual markup to help clients more
|
|
efficiently implement things like pretty printers. Most markup will be target
|
|
independent, so clients can effectively provide good display without any target
|
|
specific knowledge.
|
|
|
|
Annotated assembly goes through the normal instruction printer, but optionally
|
|
includes contextual tags on portions of the instruction string. An annotation
|
|
is any '<' '>' delimited section of text(1).
|
|
|
|
.. code-block:: bat
|
|
|
|
annotation: '<' tag-name tag-modifier-list ':' annotated-text '>'
|
|
tag-name: identifier
|
|
tag-modifier-list: comma delimited identifier list
|
|
|
|
The tag-name is an identifier which gives the type of the annotation. For the
|
|
first pass, this will be very simple, with memory references, registers, and
|
|
immediates having the tag names "mem", "reg", and "imm", respectively.
|
|
|
|
The tag-modifier-list is typically additional target-specific context, such as
|
|
register class.
|
|
|
|
Clients should accept and ignore any tag-names or tag-modifiers they do not
|
|
understand, allowing the annotations to grow in richness without breaking older
|
|
clients.
|
|
|
|
For example, a possible annotation of an ARM load of a stack-relative location
|
|
might be annotated as:
|
|
|
|
.. code-block:: nasm
|
|
|
|
ldr <reg gpr:r0>, <mem regoffset:[<reg gpr:sp>, <imm:#4>]>
|
|
|
|
|
|
1: For assembly dialects in which '<' and/or '>' are legal tokens, a literal token is escaped by following immediately with a repeat of the character. For example, a literal '<' character is output as '<<' in an annotated assembly string.
|
|
|
|
C API Details
|
|
-------------
|
|
|
|
The intended consumers of this information use the C API, therefore the new C
|
|
API function for the disassembler will be added to provide an option to produce
|
|
disassembled instructions with annotations, ``LLVMSetDisasmOptions()`` and the
|
|
``LLVMDisassembler_Option_UseMarkup`` option (see above).
|