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| -rw-r--r-- | llvm/docs/BitCodeFormat.rst | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/llvm/docs/BitCodeFormat.rst b/llvm/docs/BitCodeFormat.rst index 429c945e712..8878943b424 100644 --- a/llvm/docs/BitCodeFormat.rst +++ b/llvm/docs/BitCodeFormat.rst @@ -62,10 +62,12 @@ understanding the encoding. Magic Numbers ------------- -The first two bytes of a bitcode file are 'BC' (``0x42``, ``0x43``). The second -two bytes are an application-specific magic number. Generic bitcode tools can -look at only the first two bytes to verify the file is bitcode, while -application-specific programs will want to look at all four. +The first four bytes of a bitstream are used as an application-specific magic +number. Generic bitcode tools may look at the first four bytes to determine +whether the stream is a known stream type. However, these tools should *not* +determine whether a bitstream is valid based on its magic number alone. New +application-specific bitstream formats are being developed all the time; tools +should not reject them just because they have a hitherto unseen magic number. .. _primitives: @@ -496,12 +498,9 @@ LLVM IR Magic Number The magic number for LLVM IR files is: :raw-html:`<tt><blockquote>` -[0x0\ :sub:`4`, 0xC\ :sub:`4`, 0xE\ :sub:`4`, 0xD\ :sub:`4`] +['B'\ :sub:`8`, 'C'\ :sub:`8`, 0x0\ :sub:`4`, 0xC\ :sub:`4`, 0xE\ :sub:`4`, 0xD\ :sub:`4`] :raw-html:`</blockquote></tt>` -When combined with the bitcode magic number and viewed as bytes, this is -``"BC 0xC0DE"``. - .. _Signed VBRs: Signed VBRs |
