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[Bug rtl-optimization/63259] Detecting byteswap sequence
- From: "thopre01 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sun, 28 Sep 2014 10:09:40 +0000
- Subject: [Bug rtl-optimization/63259] Detecting byteswap sequence
- Auto-submitted: auto-generated
- References: <bug-63259-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63259
thopre01 at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
--- Comment #3 from thopre01 at gcc dot gnu.org ---
The reason is that the last gimple statement of this bswap is a rotation right
on the result of a bitwise OR. Right now bswap are searched only from bitwise
OR statement doing recursion until the source. Therefore the analysis is only
done on a subset of the statements making up this bswap.
The fix is easy but needs compilation benchmarking to make sure this doesn't
increase the cost of compiling in a noticeable way. The more statement are
considered as finishing a bswap, the closer we are to a O(nÂ) algorithm.