Re: [PATCH roland/arm-avoid-pc] ARM_BX_ALIGN_LOG2

[Roland McGrath <roland@hack.frob.com>]

> The comment should say that this should only be used in ARM-mode code 
> (certainly this definition doesn't make sense by default for code built as 
> Thumb).  OK with that change.

Well, it makes some sense for any situation doing something like what the
memcpy code is doing (i.e. arithmetically computing branch targets, which
implicitly assumes fixed distance between them).  Unless one were
completely sure that each Thumb instruction would always have a short
encoding, then you'd need to explicitly align each one to four.

I've committed it with the following comment.
Feel free to adjust it further as you see fit.


Thanks,
Roland


/* The log2 of the minimum alignment required for an address that
   is the target of a computed branch (i.e. a "bx" instruction).
   A more-specific arm-features.h file may define this to set a more
   stringent requirement.

   Using this only makes sense for code in ARM mode (where instructions
   always have a fixed size of four bytes), or for Thumb-mode code that is
   specifically aligning all the related branch targets to match (since
   Thumb instructions might be either two or four bytes).  */