Re: Excess registers pushed - regs_ever_live not right way?

["Seongbae Park (박성배, 朴成培)" <seongbae dot park at gmail dot com>]

2008/3/1 Andrew Hutchinson <andrewhutchinson@cox.net>:
> I'm am still struggling with a good solution that avoids unneeded saves
>  of parameter registers.
>
>  To solve problem all I need to know are the registers actually used for
>  parameters. Since the caller assumes all of these are clobbered by
>  callee - they should never need to be saved.

I'm totally confused what is the problem here.
I thought you were seeing extra callee-save register save/restore in prologue,
but now it sounds like you're seeing extra caller-save register save/restore.
Which one are you trying to solve, and what kind of target is this ?

>  DF_REG_DEF_COUNT is showing 1 artificial def for all POTENTIAL parameter
>  registers - not just the ones that are really used (since it uses target
>  FUNCTION_ARG_REGNO_P to get parameter registers)

You said you wanted to know if there's a def of a register within a function.
For an incoming parameter, there will be one artificial def,
and if there's no other def, it means there's no real def
of the register within the function.

>  So the DF artificial defs are useless in trying to find real parameter
>  registers.

I don't understand what you mean by this. What do you mean by
"real parameter register" ?

>  That seem to require going over all DF chains to work out which
>  registers are externally defined. DF does not solve problem for me.

What do you mean by "externally defined" ?
DF may not solve the problem for you,
but now I'm completely lost on what your problem is.

>  There has got to be an easier way of finding parameter registers used by
>  function.

If you want to find all the uses (use as in reading a register but not
writing to it),
you should look at USE chain, not DEF chain, naturally.

Seongbae