From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeffrey A Law <law@hurl.cygnus.com>
To: egcs@cygnus.com
Subject: Re: Probable bug in gcc/reg-stack.c (example given)
Date: Wed, 27 Aug 1997 03:29:01 -0000
Message-ID: <9708270329.AA19020@modi.xraylith.wisc.edu>
In-reply-to: Probable bug in gcc/reg-stack.c (example given)
X-SW-Source: 1997-08/0586.html
Message-ID: <19970827032901.oz_7MgawWEOyeXxiINjNeN0TTs3EvfpYdHbaXmvuw2g@z>

First, when looking for a set of an FP register, it seems to me
that just checking that the pattern is a (set (fp) (something))
won't work for insns like this:

(define_insn ""
  [(set (match_operand:SF 0 "nonimmediate_operand" "=f,m")
        (float_truncate:SF
         (match_operand:DF 1 "register_operand" "0,f")))
   (clobber (match_operand:SF 2 "memory_operand" "m,m"))]
  "TARGET_80387"

It seems to me you should use reg_set_p when you're looking
for a set of an FP register and for a set of the PC register.

Or, you need to iterate through each item in a PARALLEL and
do the check for (set (fp) (something))

I also think your patch will pessimize the code when it
runs into a jump table.  I think this can be easily solved
too (look in flow.c I think you can actually crib a lot of
the code from find_basic_blocks).

jeff