[HeterogeneousDWARF] Drop DW_AT_active_lane encoding and DW_AT_augmentation

[scott.linder]

Summary

A collision means we need to update the DW_AT_active_lane and
DW_AT_augmentation encodings.

The DWARF committee has expressed concern about the augmentation
attribute, so we remove it entirely.

The DW_AT_active_lane has not been produced by the compiler yet, so we
move its encoding to TBA.

[jmmartinez]

llvm/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst

3667

Good catch!

llvm/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst

 that define source language memory classes. Support is added to define language
 specific memory spaces so they can be used in a consistent way by consumers.
 
 Support for using memory spaces in defining source language types and data
 object allocation is also added.
 
 See :ref:`amdgpu-dwarf-memory-spaces`.
 
-2.15 Define Augmentation Strings to Support Multiple Extensions
----------------------------------------------------------------
-
-A ``DW_AT_LLVM_augmentation`` attribute is added to a compilation unit debugger
-information entry to indicate that there is additional target architecture
-specific information in the debugging information entries of that compilation
-unit. This allows a consumer to know what extensions are present in the debugger
-information entries as is possible with the augmentation string of other
-sections. See .
-
-The format that should be used for an augmentation string is also recommended.
-This allows a consumer to parse the string when it contains information from
-multiple vendors. Augmentation strings occur in the ``DW_AT_LLVM_augmentation``
-attribute, in the lookup by name table, and in the CFI Common Information Entry
-(CIE).
-
-See :ref:`amdgpu-dwarf-full-and-partial-compilation-unit-entries`,
-:ref:`amdgpu-dwarf-name-index-section-header`, and
-:ref:`amdgpu-dwarf-structure_of-call-frame-information`.
-
 2.16 Support Embedding Source Text for Online Compilation
 ---------------------------------------------------------
 
 AMDGPU supports programming languages that include online compilation where the
 source text may be created at runtime. For example, the OpenCL and HIP language
 runtimes support online compilation. To support is, a way to embed the source
 text in the debug information is provided.
 

 
 .. table:: Attribute names
    :name: amdgpu-dwarf-attribute-names-table
 
    ============================ ====================================
    Attribute                    Usage
    ============================ ====================================
    ``DW_AT_LLVM_active_lane``   SIMT active lanes (see :ref:`amdgpu-dwarf-low-level-information`)
-   ``DW_AT_LLVM_augmentation``  Compilation unit augmentation string (see :ref:`amdgpu-dwarf-full-and-partial-compilation-unit-entries`)
    ``DW_AT_LLVM_lane_pc``       SIMT lane program location (see :ref:`amdgpu-dwarf-low-level-information`)
    ``DW_AT_LLVM_lanes``         SIMT lane count (see :ref:`amdgpu-dwarf-low-level-information`)
    ``DW_AT_LLVM_iterations``    Concurrent iteration count (see :ref:`amdgpu-dwarf-low-level-information`)
    ``DW_AT_LLVM_vector_size``   Base type vector size (see :ref:`amdgpu-dwarf-base-type-entries`)
    ``DW_AT_LLVM_address_space`` Architecture specific address space (see :ref:`amdgpu-dwarf-address-spaces`)
    ``DW_AT_LLVM_memory_space``  Pointer or reference types (see 5.3 "Type Modifier Entries")
                                 Data objects (see 4.1 "Data Object Entries")
    ============================ ====================================
.. table:: Language Names
    Language Name        Meaning
    ==================== =============================
    ``DW_LANG_LLVM_HIP`` HIP Language.
    ==================== =============================
 
 The HIP language [:ref:`HIP <amdgpu-dwarf-HIP>`] can be supported by extending
 the C++ language.
 
-.. note::
-
-  The following new attribute is added.
-
-1.  A ``DW_TAG_compile_unit`` debugger information entry for a compilation unit
-    may have a ``DW_AT_LLVM_augmentation`` attribute, whose value is an
-    augmentation string.
-
-    *The augmentation string allows producers to indicate that there is
-    additional vendor or target specific information in the debugging
-    information entries. For example, this might be information about the
-    version of vendor specific extensions that are being used.*
-
-    If not present, or if the string is empty, then the compilation unit has no
-    augmentation string.
-
-    The format for the augmentation string is:
-
-      | ``[``\ *vendor*\ ``:v``\ *X*\ ``.``\ *Y*\ [\ ``:``\ *options*\ ]\ ``]``\ *
-
-    Where *vendor* is the producer, ``vX.Y`` specifies the major X and minor Y
-    version number of the extensions used, and *options* is an optional string
-    providing additional information about the extensions. The version number
-    must conform to semantic versioning [:ref:`SEMVER <amdgpu-dwarf-SEMVER>`].
-    The *options* string must not contain the "\ ``]``\ " character.
-
-    For example:
-
-      ::
-
-        [abc:v0.0][def:v1.2:feature-a=on,feature-b=3]
-
 A.3.3 Subroutine and Entry Point Entries
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 .. _amdgpu-dwarf-low-level-information:
 
 A.3.3.5 Low-Level Information
 +++++++++++++++++++++++++++++
 
.. note::
       ``DW_AT_location`` could be used with a DWARF expression that produces an
       implicit location description now that any location description can be
       used within a DWARF expression. This allows the ``DW_OP_call*`` operations
       to be used to push the location description of any variable regardless of
       how it is optimized.
 
 3.  ``DW_AT_LLVM_memory_space``
 
-    A ``DW_AT_memory_space`` attribute with a constant value representing a source
+    A ``DW_AT_LLVM_memory_space`` attribute with a constant value representing a source
     language specific DWARF memory space (see 2.14 "Memory Spaces"). If omitted,
-    defaults to ``DW_MSPACE_none``.
+    defaults to ``DW_MSPACE_LLVM_none``.
 
 
 A.4.2 Common Block Entries
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 A common block entry also has a ``DW_AT_location`` attribute whose value is a
 DWARF expression E that describes the location of the common block at run-time.
 The result of the attribute is obtained by evaluating E with a context that has

 defines a named subprogram, label, variable, type, or namespace, subject to the
 following rules:
 
 * ``DW_TAG_variable`` debugging information entries with a ``DW_AT_location``
   attribute that includes a ``DW_OP_addr``, ``DW_OP_LLVM_form_aspace_address``,
   or ``DW_OP_form_tls_address`` operation are included; otherwise, they are
   excluded.
 
-A.6.1.1.4 Data Representation of the Name Index
-###############################################
-
-.. _amdgpu-dwarf-name-index-section-header:
-
-
-A.6.1.1.4.1 Section Header
-^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-.. note::
-
-  The following provides an addition to DWARF Version 5 section 6.1.1.4.1 item
-  14 ``augmentation_string``.
-
-A null-terminated UTF-8 vendor specific augmentation string, which provides
-additional information about the contents of this index. If provided, the
-recommended format for augmentation string is:
-
-  | ``[``\ *vendor*\ ``:v``\ *X*\ ``.``\ *Y*\ [\ ``:``\ *options*\ ]\ ``]``\ *
-
-Where *vendor* is the producer, ``vX.Y`` specifies the major X and minor Y
-version number of the extensions used in the DWARF of the compilation unit, and
-*options* is an optional string providing additional information about the
-extensions. The version number must conform to semantic versioning [:ref:`SEMVER
-<amdgpu-dwarf-SEMVER>`]. The *options* string must not contain the "\ ``]``\ "
-character.
-
-For example:
-
-  ::
-
-    [abc:v0.0][def:v1.2:feature-a=on,feature-b=3]
-
-.. note::
-
-  This is different to the definition in DWARF Version 5 but is consistent with
-  the other augmentation strings and allows multiple vendor extensions to be
-  supported.
-
 .. _amdgpu-dwarf-line-number-information:
 
 A.6.2 Line Number Information
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 A.6.2.4 The Line Number Program Header
 ++++++++++++++++++++++++++++++++++++++
 
3.  ``version`` (ubyte)
     version number.
 
     The value of the CIE version number is 4.
 
     .. note::
 
       Would this be increased to 5 to reflect the changes in these extensions?
 
-4.  ``augmentation`` (sequence of UTF-8 characters)
-
-    A null-terminated UTF-8 string that identifies the augmentation to this CIE
-    or to the FDEs that use it. If a reader encounters an augmentation string
-    that is unexpected, then only the following fields can be read:
-
-    * CIE: length, CIE_id, version, augmentation
-    * FDE: length, CIE_pointer, initial_location, address_range
-
-    If there is no augmentation, this value is a zero byte.
-
-    *The augmentation string allows users to indicate that there is additional
-    vendor and target architecture specific information in the CIE or FDE which
-    is needed to virtually unwind a stack frame. For example, this might be
-    information about dynamically allocated data which needs to be freed on exit
-    from the routine.*
-
-    *Because the* ``.debug_frame`` *section is useful independently of any*
-    ``.debug_info`` *section, the augmentation string always uses UTF-8
-    encoding.*
-
-    The recommended format for the augmentation string is:
-
-      | ``[``\ *vendor*\ ``:v``\ *X*\ ``.``\ *Y*\ [\ ``:``\ *options*\ ]\ ``]``\ *
-
-    Where *vendor* is the producer, ``vX.Y`` specifies the major X and minor Y
-    version number of the extensions used, and *options* is an optional string
-    providing additional information about the extensions. The version number
-    must conform to semantic versioning [:ref:`SEMVER <amdgpu-dwarf-SEMVER>`].
-    The *options* string must not contain the "\ ``]``\ " character.
-
-    For example:
-
-      ::
-
-        [abc:v0.0][def:v1.2:feature-a=on,feature-b=3]
-
-5.  ``address_size`` (ubyte)
+4.  ``address_size`` (ubyte)
 
     The size of a target address in this CIE and any FDEs that use it, in bytes.
     If a compilation unit exists for this frame, its address size must match the
     address size here.
 
-6.  ``segment_selector_size`` (ubyte)
+5.  ``segment_selector_size`` (ubyte)
 
     The size of a segment selector in this CIE and any FDEs that use it, in
     bytes.
 
-7.  ``code_alignment_factor`` (unsigned LEB128)
+6.  ``code_alignment_factor`` (unsigned LEB128)
 
     A constant that is factored out of all advance location instructions (see
     :ref:`amdgpu-dwarf-row-creation-instructions`). The resulting value is
     ``(operand * code_alignment_factor)``.
 
-8.  ``data_alignment_factor`` (signed LEB128)
+7.  ``data_alignment_factor`` (signed LEB128)
 
     A constant that is factored out of certain offset instructions (see
     :ref:`amdgpu-dwarf-cfa-definition-instructions` and
     :ref:`amdgpu-dwarf-register-rule-instructions`). The resulting value is
     ``(operand * data_alignment_factor)``.
 
-9.  ``return_address_register`` (unsigned LEB128)
+8.  ``return_address_register`` (unsigned LEB128)
 
     An unsigned LEB128 constant that indicates which column in the rule table
     represents the return address of the subprogram. Note that this column might
     not correspond to an actual machine register.
 
     The value of the return address register is used to determine the program
     location of the caller frame. The program location of the top frame is the
     target architecture program counter value of the current thread.
 
-10. ``initial_instructions`` (array of ubyte)
+9.  ``initial_instructions`` (array of ubyte)
 
     A sequence of rules that are interpreted to create the initial setting of
     each column in the table.
 
     The default rule for all columns before interpretation of the initial
     instructions is the undefined rule. However, an ABI authoring body or a
     compilation system authoring body may specify an alternate default value for
     any or all columns.
 
-11. ``padding`` (array of ubyte)
+10. ``padding`` (array of ubyte)
 
     Enough ``DW_CFA_nop`` instructions to make the size of this entry match the
     length value above.
 
 An FDE contains the following fields, in order:
 
 1.  ``length`` (initial length)
 

 entry attributes.
 
 .. table:: Attribute encodings
    :name: amdgpu-dwarf-attribute-encodings-table
 
    ================================== ====== ===================================
    Attribute Name                     Value  Classes
    ================================== ====== ===================================
-   ``DW_AT_LLVM_active_lane``         0x3e08 exprloc, loclist
-   ``DW_AT_LLVM_augmentation``        0x3e09 string
    ``DW_AT_LLVM_lanes``               0x3e0a constant
    ``DW_AT_LLVM_lane_pc``             0x3e0b exprloc, loclist
    ``DW_AT_LLVM_vector_size``         0x3e0c constant
    ``DW_AT_LLVM_iterations``          0x3e0a constant, exprloc, loclist
    ``DW_AT_LLVM_address_space``       TBA    constant
    ``DW_AT_LLVM_memory_space``        TBA    constant
+   ``DW_AT_LLVM_active_lane``         TBA    exprloc, loclist
    ================================== ====== ===================================
 
 .. _amdgpu-dwarf-classes-and-forms:
 
 A.7.5.5 Classes and Forms
 +++++++++++++++++++++++++
 
 .. note::
``DW_TAG_pointer_type``            * ``DW_AT_LLVM_address_space``
                                       * ``DW_AT_LLVM_memory_space``
    ``DW_TAG_reference_type``          * ``DW_AT_LLVM_address_space``
                                       * ``DW_AT_LLVM_memory_space``
    ``DW_TAG_rvalue_reference_type``   * ``DW_AT_LLVM_address_space``
                                       * ``DW_AT_LLVM_memory_space``
    ``DW_TAG_variable``                * ``DW_AT_LLVM_memory_space``
    ``DW_TAG_formal_parameter``        * ``DW_AT_LLVM_memory_space``
    ``DW_TAG_constant``                * ``DW_AT_LLVM_memory_space``
-   ``DW_TAG_compile_unit``            * ``DW_AT_LLVM_augmentation``
    ``DW_TAG_entry_point``             * ``DW_AT_LLVM_active_lane``
                                       * ``DW_AT_LLVM_lane_pc``
                                       * ``DW_AT_LLVM_lanes``
                                       * ``DW_AT_LLVM_iterations``
    ``DW_TAG_inlined_subroutine``      * ``DW_AT_LLVM_active_lane``
                                       * ``DW_AT_LLVM_lane_pc``
                                       * ``DW_AT_LLVM_lanes``
                                       * ``DW_AT_LLVM_iterations``

llvm/docs/AMDGPUUsage.rst

 
 This is handled by defining an artificial variable for the active lane mask. The
 active lane mask artificial variable would be the actual ``EXEC`` mask for
 normal regions, and the saved execution mask for regions where the mask is
 temporarily updated. The location list expression created for this artificial
 variable is used to define the value of the ``DW_AT_LLVM_active_lane``
 attribute.
 
-``DW_AT_LLVM_augmentation``
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-For AMDGPU, the ``DW_AT_LLVM_augmentation`` attribute of a compilation unit
-debugger information entry has the following value for the augmentation string:
-
-::
-
-  [amdgpu:v0.0]
-
-The "vX.Y" specifies the major X and minor Y version number of the AMDGPU
-extensions used in the DWARF of the compilation unit. The version number
-conforms to [SEMVER]_.
-
 Call Frame Information
 ----------------------
 
 DWARF Call Frame Information (CFI) describes how a consumer can virtually
 *unwind* call frames in a running process or core dump. See DWARF Version 5
 section 6.4 and :ref:`amdgpu-dwarf-call-frame-information`.
 
 For AMDGPU, the Common Information Entry (CIE) fields have the following values:

 the return address to get the address of a byte within the call site
 instructions. See DWARF Version 5 section 6.4.4.
 
 Accelerated Access
 ------------------
 
 See DWARF Version 5 section 6.1.
 
-Lookup By Name Section Header
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-See DWARF Version 5 section 6.1.1.4.1 and :ref:`amdgpu-dwarf-lookup-by-name`.
-
-For AMDGPU the lookup by name section header table:
-
-``augmentation_string_size`` (uword)
-
-  Set to the length of the ``augmentation_string`` value which is always a
-  multiple of 4.
-
-``augmentation_string`` (sequence of UTF-8 characters)
-
-  Contains the following UTF-8 string null padded to a multiple of 4 bytes:
-
-  ::
-
-    [amdgpu:v0.0]
-
-  The "vX.Y" specifies the major X and minor Y version number of the AMDGPU
-  extensions used in the DWARF of this index. The version number conforms to
-  [SEMVER]_.
-
-  .. note::
-
-    This is different to the DWARF Version 5 definition that requires the first
-    4 characters to be the vendor ID. But this is consistent with the other
-    augmentation strings and does allow multiple vendor contributions. However,
-    backwards compatibility may be more desirable.
-
 Lookup By Address Section Header
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 See DWARF Version 5 section 6.1.2.
 
 For AMDGPU the lookup by address section header table:
 
 ``address_size`` (ubyte)