Re: [PATCH] doc: md.texi (Insn Splitting): Tweak wording for readability.

[Sandra Loosemore <sandra@codesourcery.com>]

On 3/13/23 19:25, Hans-Peter Nilsson via Gcc-patches wrote:
> Jan, did I get this right?  This was from your
> r0-36413-g6b24c25948265c / svn r44249, now on its 22nd year!
> 
> I spot-checked the pdf for readability.  Also calling on a
> doc maintainer to check grammos etc.  Ok to commit?
> 
> -- >8 --
> I needed to check what was allowed in a define_split, but
> had problems understanding what was meant by "Splitting of
> jump instruction into sequence that over by another jump
> instruction".
> 
> 	* doc/md.texi (Insn Splitting): Tweak wording for readability.

Thanks for noticing this!  I can't comment on technical correctness, but 
I do have some further suggestions on wording below.

> ---
>   gcc/doc/md.texi | 30 +++++++++++++++---------------
>   1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
> index 8e3113599fdc..786365143179 100644
> --- a/gcc/doc/md.texi
> +++ b/gcc/doc/md.texi
> @@ -8756,21 +8756,21 @@ insns that don't.  Instead, write two separate @code{define_split}
>   definitions, one for the insns that are valid and one for the insns that
>   are not valid.
>   
> -The splitter is allowed to split jump instructions into sequence of
> -jumps or create new jumps in while splitting non-jump instructions.  As
> -the control flow graph and branch prediction information needs to be updated,
> -several restriction apply.
> -
> -Splitting of jump instruction into sequence that over by another jump
> -instruction is always valid, as compiler expect identical behavior of new
> -jump.  When new sequence contains multiple jump instructions or new labels,
> -more assistance is needed.  Splitter is required to create only unconditional
> -jumps, or simple conditional jump instructions.  Additionally it must attach a
> -@code{REG_BR_PROB} note to each conditional jump.  A global variable
> -@code{split_branch_probability} holds the probability of the original branch in case
> -it was a simple conditional jump, @minus{}1 otherwise.  To simplify
> -recomputing of edge frequencies, the new sequence is required to have only
> -forward jumps to the newly created labels.
> +The splitter is allowed to split jump instructions into a sequence of jumps or
> +create new jumps while splitting non-jump instructions.  As the control flow
> +graph and branch prediction information needs to be updated, several
> +restrictions apply.

Maybe "needs to be updated after the splitter runs"?

> +
> +Splitting of a jump instruction into a sequence that has another jump
> +instruction is always valid, as the compiler expects identical behavior of the
> +new jump.  

Maybe "another jump instruction to the same label"?

> When the new sequence contains multiple jump instructions or new
> +labels, more assistance is needed.  The splitter is required to create only

s/required/permitted/

> +unconditional jumps, or simple conditional jump instructions.  Additionally it
> +must attach a @code{REG_BR_PROB} note to each conditional jump.  A global
> +variable @code{split_branch_probability} holds the probability of the original
> +branch in case it was a simple conditional jump, @minus{}1 otherwise.  To
> +simplify recomputing of edge frequencies, the new sequence is required to have
> +only forward jumps to the newly created labels.

s/required/permitted/ again
s/newly created/newly-created/

>   
>   @findex define_insn_and_split
>   For the common case where the pattern of a define_split exactly matches the

-Sandra