[Bug tree-optimization/43716] [4.6 Regression] Revision 158105 miscompiles doduc.f90

mkuvyrkov at gcc dot gnu dot org gcc-bugzilla@gcc.gnu.org
Tue Apr 13 19:32:00 GMT 2010



------- Comment #13 from mkuvyrkov at gcc dot gnu dot org  2010-04-13 19:32 -------
The SIGSEGV is due to -funsafe-math-optimizations being used with code like:
==
      Re = eps*debm*DIAhy/(vis*sec)
      reo = Re
      IF ( Re.LT.1000. ) THEN
         i1 = INT(Re/200.) + 1
      ELSEIF ( Re.LT.4000. ) THEN
         i1 = INT(Re/500.) + 4
      ELSEIF ( Re.LT.10000. ) THEN
         i1 = INT(Re/2000.) + 10
      ELSEIF ( Re.GE.30000. ) THEN
         IF ( Re.GE.49999. ) Re = 49999.D+00
         i1 = INT(Re/10000.) + 16
      ELSE
         i1 = INT(Re/5000.) + 13
      ENDIF
      i2 = i1 + 1
      y1 = y(i1)
      y2 = y(i2)
==

Here we have index `i1' calculated from fp values and then casted to int. 
Segmentation fault occurs in `y1 = y(i1)' with i1 equal to 0xffffffff8000000c. 
This is in function S00061 in doduc_red.f90, not in s33022.f90.

Also, to trigger the SIGSEGV it is necessary to compile both doduc_red.f90 and
s33022.f90 with "-O3 -funsafe-math-optimizations -ffinite-math-only".  If
either of the modules is compiled with -O2 the SIGSEGV does not occur.

While I will not argue that my patch is 100% bug-free, this seems to be an
invalid testcase.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43716



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