[Bug tree-optimization/31169] Bootstrap comparison error at revision 122821

[rth at gcc dot gnu dot org]

------- Comment #35 from rth at gcc dot gnu dot org  2007-03-29 18:21 -------
With some sed help, one can see that fold_binary is completely ruined:

-  mhi = 0x0ffffffffffffffff >> 128 - width;
-  if ((~(hi2 | hi1) & mhi) == 0) goto <L>; else goto <L>;
-
-<L>:;
-  mlo = 0x0ffffffffffffffff;
+  mhi = 0;
   goto <bb > (<L>);

Incorrect folding is surely what causes ivopts to do bad things, and bad
loop opts is the visible miscompilation problem in stage3.  Probably you
can extract sign_bit_p from any target's preprocessing and debug the 
problem.  If that's not true, I can go back and do it.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31169