From a4fb7f60e26c21596d74336e894b0bb1d2b4f15e Mon Sep 17 00:00:00 2001 From: Scott Linder Date: Thu, 23 Feb 2023 19:53:47 +0000 Subject: [PATCH] [HeterogeneousDWARF] Update encodings in AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst Repurpose the DW_OP_LLVM_aspace_implicit_pointer encoding (0xe9) as the encoding for a new operation DW_OP_LLVM_user which prefixes all other new operations. Differential Revision: https://reviews.llvm.org/D147265 --- ...GPUDwarfExtensionsForHeterogeneousDebugging.rst | 111 +++++++++++++++------ 1 file changed, 83 insertions(+), 28 deletions(-) diff --git a/llvm/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst b/llvm/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst index 37511b9..09a9daf 100644 --- a/llvm/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst +++ b/llvm/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst @@ -707,6 +707,26 @@ spaces in defining source language pointer and reference types (see :ref:`amdgpu-dwarf-type-modifier-entries`) and data object allocation (see :ref:`amdgpu-dwarf-data-object-entries`). +2.22 Expression Operation Vendor Extensibility Opcode +----------------------------------------------------- + +The vendor extension encoding space for DWARF expression operations +accommodates only 32 unique operations. In practice, the lack of a central +registry and a desire for backwards compatibility means vendor extensions are +never retired, even when standard versions are accepted into DWARF proper. This +has produced a situation where the effective encoding space available for new +vendor extensions is miniscule today. + +To expand this encoding space a new DWARF operation ``DW_OP_LLVM_user`` is +added which acts as a "prefix" for vendor extensions. It is followed by a +ULEB128 encoded vendor extension opcode, which is then followed by the operands +of the corresponding vendor extension operation. + +This approach allows all remaining operations defined in these extensions to be +encoded without conflicting with existing vendor extensions. + +See ``DW_OP_LLVM_user`` in :ref:`amdgpu-dwarf-vendor-extensions-operations`. + .. _amdgpu-dwarf-changes-relative-to-dwarf-version-5: A. Changes Relative to DWARF Version 5 @@ -724,8 +744,11 @@ A. Changes Relative to DWARF Version 5 spaces and multiple places. The names for the new operations, attributes, and constants include "\ - ``LLVM``\ " and are encoded with vendor specific codes so these extensions can - be implemented as an LLVM vendor extension to DWARF Version 5. + ``LLVM``\ " and are encoded with vendor specific codes so these extensions + can be implemented as an LLVM vendor extension to DWARF Version 5. New + operations other than ``DW_OP_LLVM_user`` are "prefixed" by + ``DW_OP_LLVM_user`` to make enough encoding space available for their + implementation. .. note:: @@ -1319,6 +1342,22 @@ specifies the byte count. It can be used: * and in location list entries (see :ref:`amdgpu-dwarf-location-list-expressions`). +.. _amdgpu-dwarf-vendor-extensions-operations: + +A.2.5.4.0 Vendor Extension Operations +##################################### + +1. ``DW_OP_LLVM_user`` + + ``DW_OP_LLVM_user`` encodes a vendor extension operation. It has at least one + operand: a ULEB128 constant identifying a vendor extension operation. The + remaining operands are defined by the vendor extension. The vendor extension + opcode 0 is reserved and cannot be used by any vendor extension. + + *The DW_OP_user encoding space can be understood to supplement the space + defined by DW_OP_lo_user and DW_OP_hi_user that is allocated by the standard + for the same purpose.* + .. _amdgpu-dwarf-stack-operations: A.2.5.4.1 Stack Operations @@ -4771,42 +4810,58 @@ A.7.7.1 Operation Expressions Rename DWARF Version 5 section 7.7.1 and delete section 7.7.2 to reflect the unification of location descriptions into DWARF expressions. - This augments DWARF Version 5 section 7.7.1 and Table 7.9. + This augments DWARF Version 5 section 7.7.1 and Table 7.9, and adds a new + table describing vendor extension operations for ``DW_OP_LLVM_user``. A DWARF operation expression is stored in a block of contiguous bytes. The bytes form a sequence of operations. Each operation is a 1-byte code that identifies -that operation, followed by zero or more bytes of additional data. The encodings -for the operations are described in -:ref:`amdgpu-dwarf-operation-encodings-table`. +that operation, followed by zero or more bytes of additional data. The encoding +for the operation ``DW_OP_LLVM_user`` is described in +:ref:`amdgpu-dwarf-operation-encodings-table`, and the encoding of all +``DW_OP_LLVM_user`` vendor extensions operations are described in +:ref:`amdgpu-dwarf-dw-op-llvm-user-vendor-extension-operation-encodings-table`. .. table:: DWARF Operation Encodings :name: amdgpu-dwarf-operation-encodings-table - ====================================== ===== ======== =============================== + ====================================== ===== ======== ========================================================================================= Operation Code Number Notes of Operands - ====================================== ===== ======== =============================== - ``DW_OP_LLVM_form_aspace_address`` 0xe1 0 - ``DW_OP_LLVM_push_lane`` 0xe2 0 - ``DW_OP_LLVM_offset`` 0xe3 0 - ``DW_OP_LLVM_offset_uconst`` 0xe4 1 ULEB128 byte displacement - ``DW_OP_LLVM_bit_offset`` 0xe5 0 - ``DW_OP_LLVM_call_frame_entry_reg`` 0xe6 1 ULEB128 register number - ``DW_OP_LLVM_undefined`` 0xe7 0 - ``DW_OP_LLVM_aspace_bregx`` 0xe8 2 ULEB128 register number, - ULEB128 byte displacement - ``DW_OP_LLVM_aspace_implicit_pointer`` 0xe9 2 4-byte or 8-byte offset of DIE, - SLEB128 byte displacement - ``DW_OP_LLVM_piece_end`` 0xea 0 - ``DW_OP_LLVM_extend`` 0xeb 2 ULEB128 bit size, - ULEB128 count - ``DW_OP_LLVM_select_bit_piece`` 0xec 2 ULEB128 bit size, - ULEB128 count - ``DW_OP_LLVM_push_iteration`` TBA 0 - ``DW_OP_LLVM_overlay`` TBA 0 - ``DW_OP_LLVM_bit_overlay`` TBA 0 - ====================================== ===== ======== =============================== + ====================================== ===== ======== ========================================================================================= + ``DW_OP_LLVM_user`` 0xe9 1+ ULEB128 vendor extension opcode, followed by vendor extension operands + defined in :ref:`amdgpu-dwarf-dw-op-llvm-user-vendor-extension-operation-encodings-table` + ====================================== ===== ======== ========================================================================================= + +.. table:: DWARF DW_OP_LLVM_user Vendor Extension Operation Encodings + :name: amdgpu-dwarf-dw-op-llvm-user-vendor-extension-operation-encodings-table + + ====================================== ========= ========== =============================== + Operation Vendor Number Notes + Extension of + Opcode Additional + Operands + ====================================== ========= ========== =============================== + ``DW_OP_LLVM_form_aspace_address`` 0x02 0 + ``DW_OP_LLVM_push_lane`` 0x03 0 + ``DW_OP_LLVM_offset`` 0x04 0 + ``DW_OP_LLVM_offset_uconst`` 0x05 1 ULEB128 byte displacement + ``DW_OP_LLVM_bit_offset`` 0x06 0 + ``DW_OP_LLVM_call_frame_entry_reg`` 0x07 1 ULEB128 register number + ``DW_OP_LLVM_undefined`` 0x08 0 + ``DW_OP_LLVM_aspace_bregx`` 0x09 2 ULEB128 register number, + SLEB128 byte displacement + ``DW_OP_LLVM_piece_end`` 0x0a 0 + ``DW_OP_LLVM_extend`` 0x0b 2 ULEB128 bit size, + ULEB128 count + ``DW_OP_LLVM_select_bit_piece`` 0x0c 2 ULEB128 bit size, + ULEB128 count + ``DW_OP_LLVM_aspace_implicit_pointer`` TBA 2 4-byte or 8-byte offset of DIE, + SLEB128 byte displacement + ``DW_OP_LLVM_push_iteration`` TBA 0 + ``DW_OP_LLVM_overlay`` TBA 0 + ``DW_OP_LLVM_bit_overlay`` TBA 0 + ====================================== ========= ========== =============================== A.7.7.3 Location List Expressions +++++++++++++++++++++++++++++++++ -- 2.7.4