Re: Non-call exceptions versus cse

[Jan Hubicka <jh at suse dot cz>]

> Jan Hubicka writes:
>  > Alternate is of course to keep value of destionation on trap undefined
>  > and always use the temporary.  The transofrmation in question is not
>  > CSE, but backward copy propagation.  I think CSE handles it by:
>  >   /* Special handling for (set REG0 REG1) where REG0 is the
>  >      "cheapest", cheaper than REG1.  After cse, REG1 will probably not
>  >       be used in the sequel, so (if easily done) change this insn to
>  >       (set REG1 REG0) and replace REG1 with REG0 in the previous insn
>  >       that computed their value.  Then REG1 will become a dead store
>  >       and won't cloud the situation for later optimizations. */
>  > But that code laready checks for basic block boundary via INSN_BASIC_BLOCK
>  > note that should be threre.
> 
> I just added that code for exactly this case.
> 
>  > Where exactly in CSE the instruction is transformed?
> 
> It doesn't do it any more.
I see.   What is the problem then?

Honza
> 
> Andrew.