optimization bug

[Weiwen Liu]

Hi, 

After applying your patch to egcs-970917/egcs-970922, gcc fails to
compile redisplay-x.c in xemacs-20.2 while running

cc1 redisplay-x.i -quiet -dumpbase redisplay-x.c -O3 
-version -o redisplay-x.s

My patch works fine and should be used instead.

The file redisplay-x.i is too long and I do not think I should send it to
the whole egcs list. I will send it to you if you need it.

Regards,

Weiwen

On Tue, 23 Sep 1997, Jim Wilson wrote:

> I have a patch that fixes the problem by eliminating the unnecessary USE
> insns.  I am not sure how safe this patch is though.  Modifying combine to
> increment REG_N_REFS if it emits a USE insn is much safer, but may result
> is poorer code because of its affect on register allocation.
> 
> There are two separate bugs here that needed to be fixed to make the testcase
> work.
>