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|
========================================
Machine IR (MIR) Format Reference Manual
========================================
.. contents::
:local:
.. warning::
This is a work in progress.
Introduction
============
This document is a reference manual for the Machine IR (MIR) serialization
format. MIR is a human readable serialization format that is used to represent
LLVM's :ref:`machine specific intermediate representation
<machine code representation>`.
The MIR serialization format is designed to be used for testing the code
generation passes in LLVM.
Overview
========
The MIR serialization format uses a YAML container. YAML is a standard
data serialization language, and the full YAML language spec can be read at
`yaml.org
<http://www.yaml.org/spec/1.2/spec.html#Introduction>`_.
A MIR file is split up into a series of `YAML documents`_. The first document
can contain an optional embedded LLVM IR module, and the rest of the documents
contain the serialized machine functions.
.. _YAML documents: http://www.yaml.org/spec/1.2/spec.html#id2800132
High Level Structure
====================
Embedded Module
---------------
When the first YAML document contains a `YAML block literal string`_, the MIR
parser will treat this string as an LLVM assembly language string that
represents an embedded LLVM IR module.
Here is an example of a YAML document that contains an LLVM module:
.. code-block:: llvm
--- |
define i32 @inc(i32* %x) {
entry:
%0 = load i32, i32* %x
%1 = add i32 %0, 1
store i32 %1, i32* %x
ret i32 %1
}
...
.. _YAML block literal string: http://www.yaml.org/spec/1.2/spec.html#id2795688
Machine Functions
-----------------
The remaining YAML documents contain the machine functions. This is an example
of such YAML document:
.. code-block:: yaml
---
name: inc
tracksRegLiveness: true
liveins:
- { reg: '%rdi' }
body:
- id: 0
name: entry
liveins: [ '%rdi' ]
instructions:
- '%eax = MOV32rm %rdi, 1, _, 0, _'
- '%eax = INC32r killed %eax, implicit-def dead %eflags'
- 'MOV32mr killed %rdi, 1, _, 0, _, %eax'
- 'RETQ %eax'
...
The document above consists of attributes that represent the various
properties and data structures in a machine function.
The attribute ``name`` is required, and its value should be identical to the
name of a function that this machine function is based on.
The attribute ``body`` contains a list of YAML mappings that represent the
function's machine basic blocks.
The first machine basic block in the ``body`` list above contains the attribute
``instructions``. This attribute stores a list of string literals which
represent the machine instructions for that basic block.
.. TODO: Describe the parsers default behaviour when optional YAML attributes
are missing.
.. TODO: Describe the syntax of the machine instructions.
.. TODO: Describe the syntax of the immediate machine operands.
.. TODO: Describe the syntax of the register machine operands.
.. TODO: Describe the syntax of the virtual register operands and their YAML
definitions.
.. TODO: Describe the syntax of the register operand flags and the subregisters.
.. TODO: Describe the machine function's YAML flag attributes.
.. TODO: Describe the machine basic block's YAML flag, successors and livein
attributes. Describe the syntax for the machine basic block operands.
.. TODO: Describe the syntax for the global value, external symbol and register
mask machine operands.
.. TODO: Describe the frame information YAML mapping.
.. TODO: Describe the syntax of the stack object machine operands and their
YAML definitions.
.. TODO: Describe the syntax of the constant pool machine operands and their
YAML definitions.
.. TODO: Describe the syntax of the jump table machine operands and their
YAML definitions.
.. TODO: Describe the syntax of the block address machine operands.
.. TODO: Describe the syntax of the CFI index machine operands.
.. TODO: Describe the syntax of the metadata machine operands, and the
instructions debug location attribute.
.. TODO: Describe the syntax of the target index machine operands.
.. TODO: Describe the syntax of the register live out machine operands.
.. TODO: Describe the syntax of the machine memory operands.
|
