[Bug tree-optimization/20643] Tree loop optimizer does worse job than RTL loop optimizer

["dberlin at dberlin dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From dberlin at gcc dot gnu dot org  2005-03-26 00:02 -------
Subject: Re:  New: Tree loop optimizer does
	worse job than RTL loop optimizer

On Fri, 2005-03-25 at 22:21 +0000, sje at cup dot hp dot com wrote:
> In the attached test case, 3.4.* GCC generates better code than 4.0 (or 4.1)
> because it moves more loop invariant code out of the inner loop of P7Viterbi. 
> The problem seems to be in the alias analysis which determines what can be moved
> out of that loop.  If you change the field M, which is unused, from int to float
> then the 4.* GCC generates better code.  I tried the structure-alias branch to
> see if that helped and it didn't. 

Structure aliasing can't disambiguate this yet. It will soon enough.

I haven't been putting the remainder of the part2 work on the
struct-aliasing branch because it's all of one file and a very small
amount of integration work, and it wasn't worth keeping merges up to
date for it.





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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20643