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[Bug rtl-optimization/21970] [3.4 only] Inline keyword causes computation to erroneously reduce to a constant
- From: "para at cfl dot rr dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 5 Jul 2005 14:40:11 -0000
- Subject: [Bug rtl-optimization/21970] [3.4 only] Inline keyword causes computation to erroneously reduce to a constant
- References: <20050608225942.21970.para@cfl.rr.com>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From para at cfl dot rr dot com 2005-07-05 14:40 -------
The analysis is slightly flawed. For example:
UINT32 r0045025C = opt_and(ic, r004501D4); // N = and (_, M) :00022108
UINT32 r00450994 = opt_not(r0045025C); // b = not (N) :fffddef7
Since you are using 1s to represent bits that are known to be 0 and 0s to
represent bits whose value are completely unknown, b should be 00000000. All
known 0s flip to 1s, and you can say nothing about the other bits because their
values are all unknown.
However, I ran my own analysis and came to the same conclusion. It seems that
the mistake was mine as I was using and (&) instead of add (+) for the round
key. My appologies. Interestingly, GCC 4.0 does *not* catch this optimization
opportunity.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21970