"``anyregcc``" - Dynamic calling convention for code patching
This is a special convention that supports patching an arbitrary code
sequence in place of a call site. This convention forces the call
- arguments into registers but allows them to be dynamcially
+ arguments into registers but allows them to be dynamically
allocated. This can currently only be used with calls to
llvm.experimental.patchpoint because only this intrinsic records
the location of its arguments in a side table. See :doc:`StackMaps`.
"``preserve_mostcc``" - The `PreserveMost` calling convention
- This calling convention attempts to make the code in the caller as little
- intrusive as possible. This calling convention behaves identical to the `C`
+ This calling convention attempts to make the code in the caller as
+ unintrusive as possible. This convention behaves identically to the `C`
calling convention on how arguments and return values are passed, but it
uses a different set of caller/callee-saved registers. This alleviates the
burden of saving and recovering a large register set before and after the
This indicates that the parameter or return pointer is not null. This
attribute may only be applied to pointer typed parameters. This is not
checked or enforced by LLVM, the caller must ensure that the pointer
- passed in is non-null, or the callee must ensure that the returned pointer
+ passed in is non-null, or the callee must ensure that the returned pointer
is non-null.
``dereferenceable(<n>)``
array), however ``dereferenceable(<n>)`` does imply ``nonnull`` in
``addrspace(0)`` (which is the default address space).
+``dereferenceable_or_null(<n>)``
+ This indicates that the parameter or return value isn't both
+ non-null and non-dereferenceable (up to ``<n>`` bytes) at the same
+ time. All non-null pointers tagged with
+ ``dereferenceable_or_null(<n>)`` are ``dereferenceable(<n>)``.
+ For address space 0 ``dereferenceable_or_null(<n>)`` implies that
+ a pointer is exactly one of ``dereferenceable(<n>)`` or ``null``,
+ and in other address spaces ``dereferenceable_or_null(<n>)``
+ implies that a pointer is at least one of ``dereferenceable(<n>)``
+ or ``null`` (i.e. it may be both ``null`` and
+ ``dereferenceable(<n>)``). This attribute may only be applied to
+ pointer typed parameters.
+
.. _gc:
Garbage Collector Strategy Names
define void @f() gc "name" { ... }
-The supported values of *name* includes those :ref:`built in to LLVM
+The supported values of *name* includes those :ref:`built in to LLVM
<builtin-gc-strategies>` and any provided by loaded plugins. Specifying a GC
-strategy will cause the compiler to alter its output in order to support the
-named garbage collection algorithm. Note that LLVM itself does not contain a
+strategy will cause the compiler to alter its output in order to support the
+named garbage collection algorithm. Note that LLVM itself does not contain a
garbage collector, this functionality is restricted to generating machine code
-which can interoperate with a collector provided externally.
+which can interoperate with a collector provided externally.
.. _prefixdata:
Instead, if specified, the target data layout is required to match what
the ultimate *code generator* expects. This string is used by the
mid-level optimizers to improve code, and this only works if it matches
-what the ultimate code generator uses. If you would like to generate IR
-that does not embed this target-specific detail into the IR, then you
-don't have to specify the string. This will disable some optimizations
-that require precise layout information, but this also prevents those
-optimizations from introducing target specificity into the IR.
+what the ultimate code generator uses. There is no way to generate IR
+that does not embed this target-specific detail into the IR. If you
+don't specify the string, the default specifications will be used to
+generate a Data Layout and the optimization phases will operate
+accordingly and introduce target specificity into the IR with respect to
+these default specifications.
.. _langref_triple:
More information about specific metadata nodes recognized by the
optimizers and code generator is found below.
+.. _specialized-metadata:
+
Specialized Metadata Nodes
^^^^^^^^^^^^^^^^^^^^^^^^^^
These aren't inherently debug info centric, but currently all the specialized
metadata nodes are related to debug info.
+.. _MDCompileUnit:
+
MDCompileUnit
"""""""""""""
enums: !2, retainedTypes: !3, subprograms: !4,
globals: !5, imports: !6)
+Compile unit descriptors provide the root scope for objects declared in a
+specific compilation unit. File descriptors are defined using this scope.
+These descriptors are collected by a named metadata ``!llvm.dbg.cu``. They
+keep track of subprograms, global variables, type information, and imported
+entities (declarations and namespaces).
+
+.. _MDFile:
+
MDFile
""""""
!0 = !MDFile(filename: "path/to/file", directory: "/path/to/dir")
+Files are sometimes used in ``scope:`` fields, and are the only valid target
+for ``file:`` fields.
+
.. _MDLocation:
MDBasicType
"""""""""""
-``MDBasicType`` nodes represent primitive types. ``tag:`` defaults to
-``DW_TAG_base_type``.
+``MDBasicType`` nodes represent primitive types, such as ``int``, ``bool`` and
+``float``. ``tag:`` defaults to ``DW_TAG_base_type``.
.. code-block:: llvm
encoding: DW_ATE_unsigned_char)
!1 = !MDBasicType(tag: DW_TAG_unspecified_type, name: "decltype(nullptr)")
+The ``encoding:`` describes the details of the type. Usually it's one of the
+following:
+
+.. code-block:: llvm
+
+ DW_ATE_address = 1
+ DW_ATE_boolean = 2
+ DW_ATE_float = 4
+ DW_ATE_signed = 5
+ DW_ATE_signed_char = 6
+ DW_ATE_unsigned = 7
+ DW_ATE_unsigned_char = 8
+
.. _MDSubroutineType:
MDSubroutineType
!1 = !BasicType(name: "char", size: 8, align: 8, DW_ATE_signed_char)
!2 = !MDSubroutineType(types: !{null, !0, !1}) ; void (int, char)
+.. _MDDerivedType:
+
MDDerivedType
"""""""""""""
!1 = !MDDerivedType(tag: DW_TAG_pointer_type, baseType: !0, size: 32,
align: 32)
+The following ``tag:`` values are valid:
+
+.. code-block:: llvm
+
+ DW_TAG_formal_parameter = 5
+ DW_TAG_member = 13
+ DW_TAG_pointer_type = 15
+ DW_TAG_reference_type = 16
+ DW_TAG_typedef = 22
+ DW_TAG_ptr_to_member_type = 31
+ DW_TAG_const_type = 38
+ DW_TAG_volatile_type = 53
+ DW_TAG_restrict_type = 55
+
+``DW_TAG_member`` is used to define a member of a :ref:`composite type
+<MDCompositeType>` or :ref:`subprogram <MDSubprogram>`. The type of the member
+is the ``baseType:``. The ``offset:`` is the member's bit offset.
+``DW_TAG_formal_parameter`` is used to define a member which is a formal
+argument of a subprogram.
+
+``DW_TAG_typedef`` is used to provide a name for the ``baseType:``.
+
+``DW_TAG_pointer_type``, ``DW_TAG_reference_type``, ``DW_TAG_const_type``,
+``DW_TAG_volatile_type`` and ``DW_TAG_restrict_type`` are used to qualify the
+``baseType:``.
+
+Note that the ``void *`` type is expressed as a type derived from NULL.
+
.. _MDCompositeType:
MDCompositeType
line: 2, size: 32, align: 32, identifier: "_M4Enum",
elements: !{!0, !1, !2})
+The following ``tag:`` values are valid:
+
+.. code-block:: llvm
+
+ DW_TAG_array_type = 1
+ DW_TAG_class_type = 2
+ DW_TAG_enumeration_type = 4
+ DW_TAG_structure_type = 19
+ DW_TAG_union_type = 23
+ DW_TAG_subroutine_type = 21
+ DW_TAG_inheritance = 28
+
+
+For ``DW_TAG_array_type``, the ``elements:`` should be :ref:`subrange
+descriptors <MDSubrange>`, each representing the range of subscripts at that
+level of indexing. The ``DIFlagVector`` flag to ``flags:`` indicates that an
+array type is a native packed vector.
+
+For ``DW_TAG_enumeration_type``, the ``elements:`` should be :ref:`enumerator
+descriptors <MDEnumerator>`, each representing the definition of an enumeration
+value for the set. All enumeration type descriptors are collected in the
+``enums:`` field of the :ref:`compile unit <MDCompileUnit>`.
+
+For ``DW_TAG_structure_type``, ``DW_TAG_class_type``, and
+``DW_TAG_union_type``, the ``elements:`` should be :ref:`derived types
+<MDDerivedType>` with ``tag: DW_TAG_member`` or ``tag: DW_TAG_inheritance``.
+
+.. _MDSubrange:
+
MDSubrange
""""""""""
!1 = !MDSubrange(count: 5, lowerBound: 1) ; array counting from 1
!2 = !MDSubrange(count: -1) ; empty array.
+.. _MDEnumerator:
+
MDEnumerator
""""""""""""
isDefinition: false, variable: i32* @foo,
declaration: !4)
+All global variables should be referenced by the `globals:` field of a
+:ref:`compile unit <MDCompileUnit>`.
+
.. _MDSubprogram:
MDSubprogram
MDLexicalBlock
""""""""""""""
-``MDLexicalBlock`` nodes represent lexical blocks in the source language (a
-scope).
+``MDLexicalBlock`` nodes describe nested blocks within a :ref:`subprogram
+<MDSubprogram>`. The line number and column numbers are used to dinstinguish
+two lexical blocks at same depth. They are valid targets for ``scope:``
+fields.
.. code-block:: llvm
- !0 = !MDLexicalBlock(scope: !1, file: !2, line: 7, column: 35)
+ !0 = distinct !MDLexicalBlock(scope: !1, file: !2, line: 7, column: 35)
+
+Usually lexical blocks are ``distinct`` to prevent node merging based on
+operands.
.. _MDLexicalBlockFile:
specifies the argument position, and this variable will be included in the
``variables:`` field of its :ref:`MDSubprogram`.
-If set, the ``inlinedAt:`` field points at an :ref:`MDLocation`, and the
-variable represents an inlined version of a variable (with all other fields
-duplicated from the non-inlined version).
-
.. code-block:: llvm
!0 = !MDLocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 0,
scope: !3, file: !2, line: 7, type: !3,
- flags: DIFlagArtificial, inlinedAt: !4)
+ flags: DIFlagArtificial)
!1 = !MDLocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 1,
- scope: !4, file: !2, line: 7, type: !3,
- inlinedAt: !6)
+ scope: !4, file: !2, line: 7, type: !3)
!1 = !MDLocalVariable(tag: DW_TAG_auto_variable, name: "y",
- scope: !5, file: !2, line: 7, type: !3,
- inlinedAt: !6)
+ scope: !5, file: !2, line: 7, type: !3)
MDExpression
""""""""""""
``noalias`` metadata can specifically be specified not to alias with some other
collection of memory access instructions that carry ``alias.scope`` metadata.
Each type of metadata specifies a list of scopes where each scope has an id and
-a domain. When evaluating an aliasing query, if for some some domain, the set
+a domain. When evaluating an aliasing query, if for some domain, the set
of scopes with that domain in one instruction's ``alias.scope`` list is a
subset of (or equal to) the set of scopes for that domain in another
instruction's ``noalias`` list, then the two memory accesses are assumed not to
'``llvm.mem.parallel_loop_access``' Metadata
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-The ``llvm.mem.parallel_loop_access`` metadata refers to a loop identifier,
-or metadata containing a list of loop identifiers for nested loops.
-The metadata is attached to memory accessing instructions and denotes that
-no loop carried memory dependence exist between it and other instructions denoted
+The ``llvm.mem.parallel_loop_access`` metadata refers to a loop identifier,
+or metadata containing a list of loop identifiers for nested loops.
+The metadata is attached to memory accessing instructions and denotes that
+no loop carried memory dependence exist between it and other instructions denoted
with the same loop identifier.
-Precisely, given two instructions ``m1`` and ``m2`` that both have the
-``llvm.mem.parallel_loop_access`` metadata, with ``L1`` and ``L2`` being the
-set of loops associated with that metadata, respectively, then there is no loop
-carried dependence between ``m1`` and ``m2`` for loops in both ``L1`` and
+Precisely, given two instructions ``m1`` and ``m2`` that both have the
+``llvm.mem.parallel_loop_access`` metadata, with ``L1`` and ``L2`` being the
+set of loops associated with that metadata, respectively, then there is no loop
+carried dependence between ``m1`` and ``m2`` for loops in both ``L1`` and
``L2``.
-As a special case, if all memory accessing instructions in a loop have
-``llvm.mem.parallel_loop_access`` metadata that refers to that loop, then the
-loop has no loop carried memory dependences and is considered to be a parallel
-loop.
+As a special case, if all memory accessing instructions in a loop have
+``llvm.mem.parallel_loop_access`` metadata that refers to that loop, then the
+loop has no loop carried memory dependences and is considered to be a parallel
+loop.
-Note that if not all memory access instructions have such metadata referring to
-the loop, then the loop is considered not being trivially parallel. Additional
-memory dependence analysis is required to make that determination. As a fail
-safe mechanism, this causes loops that were originally parallel to be considered
-sequential (if optimization passes that are unaware of the parallel semantics
+Note that if not all memory access instructions have such metadata referring to
+the loop, then the loop is considered not being trivially parallel. Additional
+memory dependence analysis is required to make that determination. As a fail
+safe mechanism, this causes loops that were originally parallel to be considered
+sequential (if optimization passes that are unaware of the parallel semantics
insert new memory instructions into the loop body).
Example of a loop that is considered parallel due to its correct use of
entries. The existence of the ``!invariant.load`` metadata on the
instruction tells the optimizer and code generator that the address
operand to this load points to memory which can be assumed unchanged.
-Being invariant does not imply that a location is dereferenceable,
-but it does imply that once the location is known dereferenceable
-its value is henceforth unchanging.
+Being invariant does not imply that a location is dereferenceable,
+but it does imply that once the location is known dereferenceable
+its value is henceforth unchanging.
The optional ``!nonnull`` metadata must reference a single
metadata name ``<index>`` corresponding to a metadata node with no
entries. The existence of the ``!nonnull`` metadata on the
instruction tells the optimizer that the value loaded is known to
never be null. This is analogous to the ''nonnull'' attribute
-on parameters and return values. This metadata can only be applied
-to loads of a pointer type.
+on parameters and return values. This metadata can only be applied
+to loads of a pointer type.
Semantics:
""""""""""
""""""""""
The '``ptrtoint``' instruction takes a ``value`` to cast, which must be
-a a value of type :ref:`pointer <t_pointer>` or a vector of pointers, and a
+a value of type :ref:`pointer <t_pointer>` or a vector of pointers, and a
type to cast it to ``ty2``, which must be an :ref:`integer <t_integer>` or
a vector of integers type.
--------------------------------------
LLVM's support for `Accurate Garbage Collection <GarbageCollection.html>`_
-(GC) requires the frontend to generate code containing appropriate intrinsic
-calls and select an appropriate GC strategy which knows how to lower these
+(GC) requires the frontend to generate code containing appropriate intrinsic
+calls and select an appropriate GC strategy which knows how to lower these
intrinsics in a manner which is appropriate for the target collector.
These intrinsics allow identification of :ref:`GC roots on the
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LLVM provides an second experimental set of intrinsics for describing garbage
-collection safepoints in compiled code. These intrinsics are an alternative
-to the ``llvm.gcroot`` intrinsics, but are compatible with the ones for
-:ref:`read <int_gcread>` and :ref:`write <int_gcwrite>` barriers. The
-differences in approach are covered in the `Garbage Collection with LLVM
-<GarbageCollection.html>`_ documentation. The intrinsics themselves are
+collection safepoints in compiled code. These intrinsics are an alternative
+to the ``llvm.gcroot`` intrinsics, but are compatible with the ones for
+:ref:`read <int_gcread>` and :ref:`write <int_gcwrite>` barriers. The
+differences in approach are covered in the `Garbage Collection with LLVM
+<GarbageCollection.html>`_ documentation. The intrinsics themselves are
described in :doc:`Statepoints`.
.. _int_gcroot:
::
%res = call <16 x float> @llvm.masked.load.v16f32 (<16 x float>* %ptr, i32 4, <16 x i1>%mask, <16 x float> %passthru)
-
+
;; The result of the two following instructions is identical aside from potential memory access exception
%loadlal = load <16 x float>, <16 x float>* %ptr, align 4
%res = select <16 x i1> %mask, <16 x float> %loadlal, <16 x float> %passthru
::
call void @llvm.masked.store.v16f32(<16 x float> %value, <16 x float>* %ptr, i32 4, <16 x i1> %mask)
-
+
;; The result of the following instructions is identical aside from potential data races and memory access exceptions
%oldval = load <16 x float>, <16 x float>* %ptr, align 4
%res = select <16 x i1> %mask, <16 x float> %value, <16 x float> %oldval
projects / oota-llvm.git / blobdiff