Re: asking the flow analysis not to optimize

[Joern Rennecke <amylaar at redhat dot com>]

>    The word size is 16 bit and I do n't have 16 bit
>   compare instruction on my machine. So
>  for longs (32 bits), I generate code like this ....
> 
>    1).   < clear the flags>
>    2).    sbc lo0, lo1
>    3).    sbc  hio, hi1
> 
>   So , now I jump based on the flags. But actually 
>  when I compile a sample code with optimization's on
>  the first instruction is being pulled out during flow
> analysis. So, I get the wrong code. So, how do I tell
> the flow analysis  not to delete that particular
> instruction or rtl insn (basically generated by
> emit_insn () .)

If this is a CC0 port, you have to use a single insn pattern to describe
all three machine insns.  If it is not, a better course is to use a hard
register for the flags, and make the setting and use of the flags
explicit in your insn patterns.