On Fri, Jul 15, 2016 at 1:07 PM, Bin Cheng <bin.ch...@arm.com> wrote: > Hi, > This patch removes support for -funsafe-loop-optimizations, as well as > -Wunsafe-loop-optimizations. By its name, this option does unsafe > optimizations by assuming all loops must terminate and doesn't wrap. > Unfortunately, it's not as useful as expected because: > 1) Simply assuming loop must terminate isn't enough. What we really want is > to analyze scalar evolution and loop niter bound under such assumptions. > This option does nothing in this aspect. > 2) IIRC, this option generates bogus code for some common programs, that's > why it's disabled by default even at Ofast level. > > After I sent patches handling possible infinite loops in both (scev/niter) > analyzer and vectorizer, it's a natural step to remove such options in GCC. > This patch does so by deleting code for -funsafe-loop-optimizations, as well > as -Wunsafe-loop-optimizations. It also deletes the two now useless tests, > while the option interface is preserved for backward compatibility purpose.
There are a number of bugs opened against those options, including one that I just opened rather recently: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71769 but some go back far, in this case 9 years: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34114 If you are going to remove the options, you should address open bugs related to those options.
