[Bug tree-optimization/103432] [12 regression] libjxl-0.5 is miscompiled, works fine with -fno-ipa-modref

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103432

Jan Hubicka <hubicka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Target Milestone|12.0                        |---
           Keywords|wrong-code                  |
      Known to work|11.2.0                      |
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2021-11-26
           Assignee|unassigned at gcc dot gnu.org      |hubicka at gcc dot gnu.org
                 CC|                            |hubicka at gcc dot gnu.org
          Component|ipa                         |tree-optimization

--- Comment #1 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
It fails with 
./xgcc -B ./ -O2 d.ii -fdbg-cnt=ipa_mod_ref_pta:189  -fdump-tree-all-details
-fdump-ipa-all-details
and works
./xgcc -B ./ -O2 d.ii -fdbg-cnt=ipa_mod_ref_pta:188  -fdump-tree-all-details
-fdump-ipa-all-details

The difference in optimized dump is:

 int main ()
 {
   struct DCTFrom D.11418;
@@ -2805,12 +2810,7 @@
   float x[4];
   struct DCTTo D.11356;
   struct DCTFrom D.11355;
-  float _3;
-  float _4;
-  double _6;
   struct FILE * stderr.3_8;
-  double _9;
-  struct FILE * stderr.4_11;
   float _12;
   float _13;
   double _15;
@@ -2996,30 +2996,10 @@
   {anonymous}::IDCT1DWrapper.constprop<4, 1, {anonymous}::DCTFrom,
{anonymous}::DCTTo> (&D.11400, &D.11356);
   D.11400 ={v} {CLOBBER};
   D.11356 ={v} {CLOBBER};
-  _3 = out[2];
-  _4 = _3 - 1.0e+0;
-  actual_accuracy_5 = ABS_EXPR <_4>;
-  if (actual_accuracy_5 > 9.999999974752427078783512115478515625e-7)
-    goto <bb 11>; [0.04%]
-  else
-    goto <bb 12>; [99.96%]
-
-  <bb 11> [local count: 429325]:
-  _6 = (double) actual_accuracy_5;
   stderr.3_8 = stderr;
-  fprintf (stderr.3_8, "ERROR: Too low accuracy: exp=%f act=%f\n",
9.999999974752427078783512115478515625e-7, _6);
+  fprintf (stderr.3_8, "ERROR: Too low accuracy: exp=%f act=%f\n",
9.999999974752427078783512115478515625e-7, 1.0e+0);
   exit (1);

-  <bb 12> [local count: 1072883004]:
-  _9 = (double) actual_accuracy_5;
-  stderr.4_11 = stderr;
-  fprintf (stderr.4_11, "OK: Good accuracy: exp=%f act=%f\n",
9.999999974752427078783512115478515625e-7, _9);
-  x ={v} {CLOBBER};
-  out ={v} {CLOBBER};
-  coeffs ={v} {CLOBBER};
-  scratch_space ={v} {CLOBBER};
-  return 0;
-
 }

And I suppose we are not expected to optimize out the "Good accuracy" message
:)
So it looks out is modified by  {anonymous}::IDCT1DWrapper.constprop<4, 1,
{anonymous}::DCTFrom, {anonymous}::DCTTo> (&D.11400, &D.11356);
but for some reason ipa propagation gets no_indirect_clobber for param1.  This
seems wrong since to->data is written to, so it is an indirect clobber.
I may be able to look more into this only tomorrow - it is bit late.