From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joern Rennecke To: wilson@cygnus.com (Jim Wilson) Cc: amylaar@cygnus.co.uk, egcs@cygnus.com Subject: Re: New size optimization Date: Thu, 02 Apr 1998 11:32:00 -0000 Message-id: <199804011011.LAA13532@phal.cygnus.co.uk> References: <199804010031.QAA06136@rtl.cygnus.com> X-SW-Source: 1998-04/msg00069.html > I was talking to Anthony Green about this, and he mentioned that it might be > useful to add a flag to disable loop-invariant-code-motion and then have -Os > set that flag. That is, we perhaps should make -Os work like -O2. -O2 just > sets a bunch of flags, and the user can override the choices if they are wrong > for a particular application. We should perhaps do the same for -Os, making > it set a bunch of flags that the user can override if the defaults weren't the > best possible choice. There is a tradeoff with having too many -f options > that the user gets confused though. > > Is there any reason why you just disabled the last part of the LICM code, and > not all of it? Maybe strength reduction needs some of the info computed by > LICM. Or maybe you didn't try disabling the rest of it? It is probably useful > to document why this choice was made in a comment. I didn't try disabling the rest. The patch I made is simple and allows quick testing. I don't know if disabling the rest will require any special attention on data that is used by other code; at any rate, it would require a lot of indentation changes, or lots of small changes involving the flag to test, or both. So before we do that, I think we should decide if we want a new -f option for this choice - and if yes, how its flag variable is called.