On Thu, 2005-02-24 at 12:55, Tarun Kawatra wrote: > You are write here that if some expr doesn't get into hash table, it will > not get optimized.
That was an assumption on my part. You shouldn't take it as the literal truth. I'm not an expert on all implementation details of the gcse.c pass. > But since plus expressions on x86 also clobber CC as > shown below > then why the same reasoning does not apply to plus expressions. Why will > there insertion later will not create any problems? Obviously, plus expressions will have the same problem. That is why I question whether plus expressions are properly getting optimized. Since you haven't provided any example that shows that they are being optimized, or pointed me at anything in the gcse.c file I can look at, there isn't anything more I can do to help you. All I can do is tell you that you need to give more details, or debug the problem yourself. > Actually I am trying to extend PRE implementation so that it performs > strength reduction as well. it requires multiplication expressions to get > into hash table. Current sources have a higher level intermediate language (gimple) and SSA based optimization passes that operate on them. This includes a tree-ssa-pre.c pass. It might be more useful to extend this to do strength reduction that to try to extend the RTL gcse pass. > I am debugging the code to find where the differences for the two kind of > expressions occur. > Will let you all know if I found anything interesting. Good. > If you know this already please share with me. It is unlikely that anyone already knows this info offhand. -- Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com
