gcc 2.95.2 bug: -O2 -g

[Rajeev Byrisetty]

I see the following optimization bug. I have reduced it a really small
program as below. The compiler is adding code that corrupts the caller's
stack. The same code (along with a few more instructions) is absent when
compiled with O1.

I am only seeing it in a couple of test programs that have a variant of this
"showtimes" function. Note that removing a variety of things (such as
unsigned int -> int, removing sysconf, removing the printfs) gets rid of the
problem.

offending instruction: 0x80487f3 

 <<o2bug.c>> 
Compiler details:
version: 2.95.2
compiler options: -O2 -g
----------------------------------------

]$ gdb ./o2bug 
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This GDB was configured as "i386-redhat-linux"...
(gdb) disas showtimes
Dump of assembler code for function showtimes:
0x80487e0 <showtimes>:  push   %ebp
0x80487e1 <showtimes+1>:        mov    %esp,%ebp
0x80487e3 <showtimes+3>:        sub    $0x40,%esp
0x80487e6 <showtimes+6>:        push   %edi
0x80487e7 <showtimes+7>:        push   %esi
0x80487e8 <showtimes+8>:        mov    0xc(%ebp),%edi
0x80487eb <showtimes+11>:       mov    0x10(%ebp),%eax
0x80487ee <showtimes+14>:       xor    %edx,%edx
0x80487f0 <showtimes+16>:       mov    %eax,0x10(%ebp)
0x80487f3 <showtimes+19>:       mov    %edx,0x14(%ebp)
0x80487f6 <showtimes+22>:       add    $0xfffffff4,%esp
0x80487f9 <showtimes+25>:       push   $0x2
0x80487fb <showtimes+27>:       call   0x80486ac <sysconf>
0x8048800 <showtimes+32>:       mov    %eax,%ecx
0x8048802 <showtimes+34>:       mov    $0x3e8,%edx
0x8048807 <showtimes+39>:       mov    %edx,%eax
0x8048809 <showtimes+41>:       cltd   
0x804880a <showtimes+42>:       idiv   %ecx,%eax
0x804880c <showtimes+44>:       mov    0x10(%ebp),%edx
0x804880f <showtimes+47>:       mov    %eax,%esi
0x8048811 <showtimes+49>:       add    $0xfffffff8,%esp
0x8048814 <showtimes+52>:       push   %edx
---Type <return> to continue, or q <return> to quit---q

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