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Diffstat (limited to 'docs/BitCodeFormat.rst')
| -rw-r--r-- | docs/BitCodeFormat.rst | 36 |
1 files changed, 29 insertions, 7 deletions
diff --git a/docs/BitCodeFormat.rst b/docs/BitCodeFormat.rst index fce1e37cf513..fc553f79174a 100644 --- a/docs/BitCodeFormat.rst +++ b/docs/BitCodeFormat.rst @@ -28,8 +28,9 @@ Unlike XML, the bitstream format is a binary encoding, and unlike XML it provides a mechanism for the file to self-describe "abbreviations", which are effectively size optimizations for the content. -LLVM IR files may be optionally embedded into a `wrapper`_ structure that makes -it easy to embed extra data along with LLVM IR files. +LLVM IR files may be optionally embedded into a `wrapper`_ structure, or in a +`native object file`_. Both of these mechanisms make it easy to embed extra +data along with LLVM IR files. This document first describes the LLVM bitstream format, describes the wrapper format, then describes the record structure used by LLVM IR files. @@ -460,6 +461,19 @@ to the start of the bitcode stream in the file, and the Size field is the size in bytes of the stream. CPUType is a target-specific value that can be used to encode the CPU of the target. +.. _native object file: + +Native Object File Wrapper Format +================================= + +Bitcode files for LLVM IR may also be wrapped in a native object file +(i.e. ELF, COFF, Mach-O). The bitcode must be stored in a section of the +object file named ``.llvmbc``. This wrapper format is useful for accommodating +LTO in compilation pipelines where intermediate objects must be native object +files which contain metadata in other sections. + +Not all tools support this format. + .. _encoding of LLVM IR: LLVM IR Encoding @@ -714,7 +728,7 @@ global variable. The operand fields are: * *unnamed_addr*: If present and non-zero, indicates that the variable has ``unnamed_addr`` -.. _dllstorageclass: +.. _bcdllstorageclass: * *dllstorageclass*: If present, an encoding of the DLL storage class of this variable: @@ -727,7 +741,7 @@ global variable. The operand fields are: MODULE_CODE_FUNCTION Record ^^^^^^^^^^^^^^^^^^^^^^^^^^^ -``[FUNCTION, type, callingconv, isproto, linkage, paramattr, alignment, section, visibility, gc, prefix, dllstorageclass]`` +``[FUNCTION, type, callingconv, isproto, linkage, paramattr, alignment, section, visibility, gc, prologuedata, dllstorageclass, comdat, prefixdata]`` The ``FUNCTION`` record (code 8) marks the declaration or definition of a function. The operand fields are: @@ -770,10 +784,17 @@ function. The operand fields are: * *unnamed_addr*: If present and non-zero, indicates that the function has ``unnamed_addr`` -* *prefix*: If non-zero, the value index of the prefix data for this function, +* *prologuedata*: If non-zero, the value index of the prologue data for this function, + plus 1. + +* *dllstorageclass*: An encoding of the + :ref:`dllstorageclass<bcdllstorageclass>` of this function + +* *comdat*: An encoding of the COMDAT of this function + +* *prefixdata*: If non-zero, the value index of the prefix data for this function, plus 1. -* *dllstorageclass*: An encoding of the `dllstorageclass`_ of this function MODULE_CODE_ALIAS Record ^^^^^^^^^^^^^^^^^^^^^^^^ @@ -791,7 +812,8 @@ fields are * *visibility*: If present, an encoding of the `visibility`_ of the alias -* *dllstorageclass*: If present, an encoding of the `dllstorageclass`_ of the alias +* *dllstorageclass*: If present, an encoding of the + :ref:`dllstorageclass<bcdllstorageclass>` of the alias MODULE_CODE_PURGEVALS Record ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |