[Bug rtl-optimization/31830] Input parameter trashed with optimization -O when using a union and bit field

["gmorain at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from gmorain at gmail dot com  2007-05-19 02:17 -------
(In reply to comment #2)
> I can reproduce the failure on powerpc-linux-gnu with 4.1.0 but it works on the
> trunk. combine is doing something wrong.
> 

I tested it on 4.2.0, and it works OK.  Except, I can't understand why the
stack frame is 32 bytes instead of 16.

powerpc-elf-objdump -S foo.o

foo.o:     file format elf32-powerpc

Disassembly of section .text:

00000000 <foo>:
   0:   94 21 ff e0     stwu    r1,-32(r1)
   4:   7c 08 02 a6     mflr    r0
   8:   93 a1 00 14     stw     r29,20(r1)
   c:   90 01 00 24     stw     r0,36(r1)
  10:   7c 7d 1b 78     mr      r29,r3
  14:   48 00 00 01     bl      14 <foo+0x14>
  18:   53 a3 c0 0e     rlwimi  r3,r29,24,0,7
  1c:   48 00 00 01     bl      1c <foo+0x1c>
  20:   80 01 00 24     lwz     r0,36(r1)
  24:   7c 08 03 a6     mtlr    r0
  28:   83 a1 00 14     lwz     r29,20(r1)
  2c:   38 21 00 20     addi    r1,r1,32
  30:   4e 80 00 20     blr


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31830