[Bug middle-end/54850] [4.8 Regression] FAIL: gcc.c-torture/execute/20041113-1.c execution, -Os

["pthaugen at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54850

--- Comment #5 from Pat Haugen <pthaugen at gcc dot gnu.org> 2012-10-17 23:38:16 UTC ---
I'm seeing the same thing on cpu2006 benchmark 44.namd on PowerPC64. A load is
being moved above a store to the same location, starting with revision 191493.

Reduced testcase and compile command:

[pthaugen@igoo pr54850]$ cat junk.C
// g++ -S -m64 -O2 -mcpu=power7 junk.C

class Vector {
   public:
     double x,y,z;

     //  v1 += v2;
     inline void operator+=(const Vector &v2) {
       x += v2.x;
       y += v2.y;
       z += v2.z;
     }
};


Vector* foo(Vector *p, Vector *shift, Vector *p1, int n) {
  int i;

  for(i = 0; i < n; i++) {
    p[i] = p1[i];
    p[i] += *shift;
  }
  return p;
}

[pthaugen@igoo pr54850]$ /home/pthaugen/install/gcc/temp/bin/g++ -S -m64 -O2
-mcpu=power7 junk.C


The sched1 dump correctly lists forward dependencies of the initial store(s) to
p1[i] to the subsequent loads of p1[i], but those dependencies are gone in the
.sched2 pass.

>From .sched1  (stores are insn 75,77,79, and dependent loads are insn
80,84,88):

;;   ======================================================
;;   -- basic block 4 from 74 to 96 -- before reload
;;   ======================================================

;;   --------------- forward dependences: ------------

;;   --- Region Dependences --- b 4 bb 0
;;      insn  code    bb   dep  prio  cost   reservation
;;      ----  ----    --   ---  ----  ----   -----------
;;       74   379     4     0    47     2   DU_power7,LSU_power7        : 96 92
91n 87n 83n 79n 77n 75nm
;;       76   379     4     0    45     2   DU_power7,LSU_power7        : 96 92
91n 87n 83n 79n 77nm 75n
;;       78   379     4     0    45     2   DU_power7,LSU_power7        : 96 92
91n 87n 83n 79nm 77n 75n
;;       75   379     4     3    45     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 93 89n 85n 83n 81n 80n
;;       77   379     4     3    31     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 93 89n 87n 85n 84n
;;       79   379     4     3    17     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 93 91n 89n 88n
;;       80   366     4     1    39     2   DU_power7,LSU_power7        : 96 93
83n 82
;;       81   366     4     1    39     2   DU_power7,LSU_power7        : 96
91n 87n 83n 82
;;       82   740     4     2    37     6   DU_power7,VSU_power7        : 96 83
;;       83   366     4     7    31     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 93 89n 85n
;;       84   366     4     1    25     2   DU_power7,LSU_power7        : 96 93
87n 86
;;       85   366     4     3    25     2   DU_power7,LSU_power7        : 96
91n 87n 86
;;       86   740     4     2    23     6   DU_power7,VSU_power7        : 96 87
;;       87   366     4     8    17     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 93 89n
;;       88   366     4     1    11     2   DU_power7,LSU_power7        : 96 93
91n 90



>From .sched2 pass:

;;   ======================================================
;;   -- basic block 4 from 74 to 96 -- after reload
;;   ======================================================

;;   --------------- forward dependences: ------------

;;   --- Region Dependences --- b 4 bb 0
;;      insn  code    bb   dep  prio  cost   reservation
;;      ----  ----    --   ---  ----  ----   -----------
;;       74   379     4     0    50     2   DU_power7,LSU_power7        : 96
91n 87n 83n 92 79n 77n 75nm
;;       76   379     4     0    48     2   DU_power7,LSU_power7        : 96
91n 87n 83n 92 79n 77nm 75n
;;       78   379     4     0    48     2   DU_power7,LSU_power7        : 96
91n 87n 83n 92 79nm 77n 75n
;;       75   379     4     3    48     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 89n 85n 81n 93
;;       77   379     4     3    43     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 89n 85n 93
;;       79   379     4     3    43     6   DU_power7,(LSU_power7+FXU_power7)  
: 96m 89n 93
;;       92    80     4     3     7     1   DU_power7,FXU_power7        : 96 95
;;       95   545     4     1     6     1   DU_power7,FXU_power7        : 96m
;;       93    80     4     3    43     1   DU_power7,FXU_power7        : 96 91
87 83 88 84 80
;;       81   366     4     1    42     3   DU_power7,LSU_power7        : 96
91n 87n 83n 82m
;;       80   366     4     1    42     3   DU_power7,LSU_power7        : 96
83n 88 82
;;       84   366     4     1    27     3   DU_power7,LSU_power7        : 96
87n 86
;;       82   740     4     2    39     6   DU_power7,VSU_power7        : 96 85
83 88
;;       88   366     4     3    12     3   DU_power7,LSU_power7        : 96
91n 90