[Bug middle-end/53688] [4.8 Regression] 191.fma3d in SPEC CPU 2000 miscompiled

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53688

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-18 
13:50:28 UTC ---
NEW_PAGE seems to be miscompiled - we fail to output JOB_ID_RECORD%VERSION
('SPEC CPU'), the comparison difference is lots of

@@ -146,7 +146,7 @@
   43255/3    1.1579E+03   -8.1233E+02    0.0000E+00    2.5290E+02   
0.0000E+00    0.0000E+00         1   41   1.42E+02 43255
   43255/4   -3.5068E+03   -4.3304E+03    0.0000E+00    2.0702E+04   
0.0000E+00    0.0000E+00         1   41   1.42E+02 43255
   43255/5   -3.5204E+03   -3.2181E+03    0.0000E+00    2.4813E+04   
0.0000E+00    0.0000E+00         1   41   1.42E+02 43255
-1 FMA-3D  SPEC CPU       Impulse Loaded Cylindrical Panel (w/ Subcycling) -
100MB Data Set                              Page No:  10
+1 FMA-3D                 Impulse Loaded Cylindrical Panel (w/ Subcycling) -
100MB Data Set                              Page No:  10

     Time T = 4.57200E-07   Time Step =     360
 0   NP    X-DISPLACE   Y-DISPLACE   Z-DISPLACE   X-VELOCITY   Y-VELOCITY  
Z-VELOCITY  X-ACCELERATE Y-ACCELERATE Z-ACCELERATE     NP

by inspecting with gdb you can see that JOB_ID_RECORD%VERSION is properly
populated but HEADLINE is not properly built.

It is sched2 who re-orders

(insn:TI 102 100 250 8 (parallel [
            (set (reg:DI 2 cx [143])
                (const_int 0 [0]))
            (set (reg/f:DI 5 di [141])
                (plus:DI (reg/f:DI 5 di [141])
                    (reg:DI 2 cx [143])))
            (set (mem/c:BLK (reg/f:DI 5 di [141]) [0 MEM[(void *)&headline +
9B]+0 A8])
                (const_int 0 [0]))
            (use (reg:QI 0 ax [142]))
            (use (reg:DI 2 cx [143]))
        ]) t.f90:43848 896 {*rep_stosqi}
     (expr_list:REG_UNUSED (reg/f:DI 5 di [141])
        (nil)))

and

(insn:TI 106 96 107 8 (set (mem/c:DI (const:DI (plus:DI (symbol_ref:DI
("headline.65670") [flags 0x2]  <var_decl 0x7fc398ffbdc0 headline>)
                    (const_int 10 [0xa]))) [0 MEM[(c_char * {ref-all})&headline
+ 10B]+0 S8 A16])
        (reg:DI 1 dx [orig:146 MEM[(c_char * {ref-all})&job_id_record + 12B] ]
[146])) t.f90:43850 62 {*movdi_internal_rex64}
     (expr_list:REG_DEAD (reg:DI 1 dx [orig:146 MEM[(c_char *
{ref-all})&job_id_record + 12B] ] [146])
        (nil)))

quite possibly because the MEM_ATTRs in the setmem pattern do not have
a MEM_EXPR that has a suitable size.

Testcase:

char headline[256];
struct hdr {
  char part1[9];
  char part2[8];
} p;

void __attribute__((noinline,noclone))
init()
{
  __builtin_memcpy (p.part1, "FOOBARFOO", sizeof (p.part1));
  __builtin_memcpy (p.part2, "SPEC CPU", sizeof (p.part2));
}

int main()
{
  char *x;
  int c;
  init();
  __builtin_memcpy (&headline[0], p.part1, 9);
  c = 9;
  x = &headline[0];
  x = x + c;
  __builtin_memset (x, ' ', 245);
  __builtin_memcpy (&headline[10], p.part2, 8);
  c = 18;
  x = &headline[0];
  x = x + c;
  __builtin_memset (x, ' ', 238);
  if (headline[10] != 'S')
    __builtin_abort ();
  return 0;
}