Path: blob/main/docs/source/user-guide/binding/target-information.rst
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==================
Target information
==================
.. currentmodule:: llvmlite.binding
Target information allows you to inspect and modify aspects of
the code generation, such as which CPU is targeted or what
optimization level is desired.
Minimal use of this module would be to create a
:class:`TargetMachine` for later use in code generation.
EXAMPLE::
from llvmlite import binding
target = binding.Target.from_default_triple()
target_machine = target.create_target_machine()
Functions
==========
* .. function:: get_default_triple()
Return a string representing the default target triple that
LLVM is configured to produce code for. This represents the
host's architecture and platform.
* .. function:: get_process_triple()
Return a target triple suitable for generating code for the
current process.
EXAMPLE: The default triple from ``get_default_triple()``
is not suitable when LLVM is compiled for 32-bit, but the
process is executing in 64-bit mode.
* .. function:: get_object_format(triple=None)
Get the object format for the given *triple* string, or the
default triple if ``None``. Returns a string such as
``"ELF"``, ``"COFF"`` or ``"MachO"``.
* .. function:: get_host_cpu_name()
Get the name of the host's CPU as a string. You can use the
return value with :meth:`Target.create_target_machine()`.
* .. function:: get_host_cpu_features()
Return a dictionary-like object indicating the CPU features
for the current architecture and whether they are enabled
for this CPU.
The key-value pairs contain the feature name
as a string and a boolean indicating whether the feature is
available.
The returned value is an instance of the
``FeatureMap`` class, which adds a new method
``.flatten()`` for returning a string suitable for use
as the ``features`` argument to
:meth:`Target.create_target_machine()`.
If LLVM has not implemented this feature or it fails to get
the information, a ``RuntimeError`` exception is raised.
* .. function:: create_target_data(data_layout)
Create a :class:`TargetData` representing the given
*data_layout* string.
Classes
=======
.. class:: TargetData
Provides functionality around a given data layout. It
specifies how the different types are to be represented in
memory. Use :func:`create_target_data` to instantiate.
* .. method:: get_abi_size(type)
Get the ABI-mandated size of a :class:`TypeRef` object.
Returns an integer.
* .. method:: get_abi_alignment(type)
Similar to :meth:`get_abi_size`, but returns the ABI-mandated alignment
rather that the ABI size.
* .. method:: get_pointee_abi_size(type)
Similar to :meth:`get_abi_size`, but assumes that *type* is
an LLVM pointer type and returns the ABI-mandated size of
the type pointed to. This is useful for a global
variable, whose type is really a pointer to the declared
type.
* .. method:: get_pointee_abi_alignment(type)
Similar to :meth:`get_pointee_abi_size`, but returns the
ABI-mandated alignment rather than the ABI size.
* .. method:: get_element_offset(type, position)
Computes the byte offset of the struct element at position.
.. class:: Target
Represents a compilation target. The following factories
are provided:
* .. classmethod:: from_triple(triple)
Create a new :class:`Target` instance for the given
*triple* string denoting the target platform.
* .. classmethod:: from_default_triple()
Create a new :class:`Target` instance for the default
platform that LLVM is configured to produce code for.
This is equivalent to calling
``Target.from_triple(get_default_triple())``.
The following attributes and methods are available:
* .. attribute:: description
A description of the target.
* .. attribute:: name
The name of the target.
* .. attribute:: triple
A string that uniquely identifies the target.
EXAMPLE: ``"x86_64-pc-linux-gnu"``
* .. method:: create_target_machine(cpu='', features='', \
opt=2, reloc='default', codemodel='jitdefault', \
abiname='')
Create a new :class:`TargetMachine` instance for this
target and with the given options:
* *cpu* is an optional CPU name to specialize for.
* *features* is a comma-separated list of target-specific
features to enable or disable.
* *opt* is the optimization level, from 0 to 3.
* *reloc* is the relocation model.
* *codemodel* is the code model.
* *abiname* is the name of the ABI.
The defaults for reloc and codemodel are appropriate for
JIT compilation.
TIP: To list the available CPUs and features for a
target, run the command ``llc -mcpu=help``.
.. class:: TargetMachine
Holds all the settings necessary for proper code generation,
including target information and compiler options. Instantiate
using :meth:`Target.create_target_machine`.
* .. method:: add_analysis_passes(pm)
Register analysis passes for this target machine with the
:class:`PassManager` instance *pm*.
* .. method:: emit_object(module)
Represent the compiled *module*---a :class:`ModuleRef`
instance---as a code object that is suitable for use
with the platform's linker. Returns a bytestring.
* .. method:: set_asm_verbosity(is_verbose)
Set whether this target machine emits assembly with
human-readable comments, such as those describing control
flow or debug information.
* .. method:: emit_assembly(module)
Return a string representing the compiled *module*'s native
assembler. You must first call
:func:`initialize_native_asmprinter()`.
* .. attribute:: target_data
The :class:`TargetData` associated with this target
machine.
.. class:: FeatureMap
Stores processor feature information in a dictionary-like
object. This class extends ``dict`` and adds only the
``.flatten()`` method.
.. method:: flatten(sort=True)
Returns a string representation of the stored information
that is suitable for use in the ``features`` argument of
:meth:`Target.create_target_machine()`.
If the ``sort`` keyword argument is
``True``---the default---the features are sorted by name
to give a stable ordering between Python sessions.