[Bug middle-end/107657] New: PROMOTE_MODE, TARGET_PROMOTE_FUNCTION_MODE, TARGET_FUNCTION_VALUE and TARGET_PROMOTE_FUNCTION_MODE should describe better their interactions

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107657

            Bug ID: 107657
           Summary: PROMOTE_MODE, TARGET_PROMOTE_FUNCTION_MODE,
                    TARGET_FUNCTION_VALUE and TARGET_PROMOTE_FUNCTION_MODE
                    should describe better their interactions
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: documentation
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

These 4 target macros/hooks (PROMOTE_MODE is a macro) all are related and there
should be one location which describes how they are related and examples of
when you define them.

Note the text of PROMOTE_MODE should be improved too:
Do not define this macro if it would never modify m.

I think a better way of writing that is:
If the mode m will never be changed for the target, then this macro does not
need to be defined.