------- Additional Comments From law at redhat dot com 2005-05-17 17:03 ------- Subject: Re: [4.0 Regression] Reload may generate stores to read-only memory
On Sat, 2005-05-07 at 16:52 +0000, ebotcazou at gcc dot gnu dot org wrote: > ------- Additional Comments From ebotcazou at gcc dot gnu dot org 2005-05-07 > 16:52 ------- > > I don't know that I'm in a position to make a good decision here, but I > > do agree with Jeff -- it would be a lot more compelling to make the > > change if there was actually a demonstrable problem -- especially coming > > from non-synthetic code. > > I presume you'd like to have a testcase that fails with 4.0.x? Because I can > hardly think of a more demonstrable problem than this one: Jeff's analysis for > 4.1.x was exactly the same as mine for 3.3.x and nothing has changed in the > code. It's still a relatively difficult bug to tickle. It only appeared in the mainline as a side effect of improvements to the jump threading code Block duplication followed by redundancy elimination resulted in having a pseudo-pseudo copy where the source pseudo was equivalent to a readonly mem and the RTL optimizers did not eliminate the pseudo-pseudo copy. Bernd has done some additional work on this problem and we may be converging on a better solution than simply ignoring these problematical equivalences. Jeff -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15248