An alias bug

[H.J. Lu]

>   > Here is a testcase. Compile it with -O2. You should get a core dump
>   > on x86. The problem is aliase code cannot tell in
> [ ... ]
> This one runs just fine too on my x86 compiled with -O2.
> 
> Thanks for the RTL.  It would have helped if you at least mentioned
> what function this code was from -- it was nontrivial to find this

It is the main function.

> rtl in my dump files because the insn #s don't exactly match.
> 
> Compiling with -O2 on my x86 I get this in my .greg dump in main:
> 
> (code_label/i 462 461 887 973 "")
> 
> (insn 887 462 463 (set (reg:SI 4 %esi)
>         (mem:SI (plus:SI (reg:SI 6 %ebp)
>                 (const_int -88)))) 54 {movsi+2} (nil)
>     (nil))
> 
> (insn/i:HI 463 887 464 (set (mem/s:SI (reg:SI 4 %esi))
>         (reg:SI 0 %eax)) 54 {movsi+2} (nil)
>     (expr_list:REG_DEAD (reg:SI 0 %eax)
>         (expr_list:REG_DEAD (mem:SI (plus:SI (reg:SI 6 %ebp)
>                     (const_int -88)))
>             (nil))))
> 
> [ random note insns ]
> 
> (insn 810 469 836 (set (reg:SI 1 %edx)
>         (mem:SI (plus:SI (reg:SI 6 %ebp)
>                 (const_int -68)))) 54 {movsi+2} (nil)
>     (nil))
> 
> In my .sched2 dump I get:
> 
> [ random note insns ]
> 
> (insn 887 836 463 (set (reg:SI 4 %esi)
>         (mem:SI (plus:SI (reg:SI 6 %ebp)
>                 (const_int -88)))) 54 {movsi+2} (nil)
>     (nil))
> 
> (insn/i:HI 463 887 810 (set (mem/s:SI (reg:SI 4 %esi))
>         (reg:SI 0 %eax)) 54 {movsi+2} (insn_list 887 (nil))
>     (expr_list:REG_DEAD (reg:SI 0 %eax)
>         (expr_list:REG_DEAD (mem:SI (plus:SI (reg:SI 6 %ebp)
>                     (const_int -88)))
>             (nil))))
> 
> (insn 810 463 811 (set (reg:SI 1 %edx)
>         (mem:SI (plus:SI (reg:SI 6 %ebp)
>                 (const_int -68)))) 54 {movsi+2} (nil)
>     (nil))
> 
> 
> Nothing got moved in an unsafe manner as far as I can tell.
> 

That is strange. insn is moved unsafely by egcs in CVS as of 11:00am
PDT on 980711 on my Linux/x86. BTW, I didn't use haifa-sched. I also
use -O2 -g to bootstrap egcs. BTW, have you tried "make check" on my
libg++ addon in egcs?

BTW, I have put tSet.cc and RTL dumps at

ftp://ftp.yggdrasil.com/private/hjl/tSet.tar.gz

insn/i:HI 468 and insn 823 are swapped after sched2.

-- 
H.J. Lu (hjl@gnu.org)