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