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