On Mon, Sep 3, 2012 at 6:28 AM, Richard Guenther <richard.guent...@gmail.com> wrote: > On Fri, Aug 10, 2012 at 1:30 PM, Richard Guenther <rguent...@suse.de> wrote: >> >> This adds a new optimization level, -Og, as previously discussed. >> It aims at providing fast compilation, a superior debugging >> experience and reasonable runtime performance. Instead of making >> -O1 this optimization level this adds a new -Og. >> >> It's a first cut, highlighting that our fixed pass pipeline and >> simply enabling/disabling individual passes (but not pass copies >> for example) doesn't scale to properly differentiate between >> -Og and -O[23]. -O1 should get similar treatment, eventually >> just building on -Og but not focusing on debugging experience. >> That is, I expect that in the end we will at least have two post-IPA >> optimization pipelines. It also means that you cannot enable >> PRE or VRP with -Og at the moment because these passes are not >> anywhere scheduled (similar to the situation with -O0). >> >> It has some funny effect on dump-file naming of the pass copies >> though, which hints at that the current setup is too static. >> For that reason the new queue comes after the old, to not confuse >> too many testcases. >> >> It also does not yet disable any of the early optimizations that >> make debugging harder (SRA comes to my mind here, as does >> switch-conversion and partial inlining). >> >> The question arises if we want to support in any reasonable >> way using profile-feedback or LTO for -O[01g], thus if we >> rather want to delay some of the early opts to after IPA >> optimizations. >> >> Not bootstrapped or fully tested, but it works for the compile >> torture. >> >> Comments welcome, > > No comments? Then I'll drop this idea for 4.8. >
When I debug binutils, I have to use -O0 -g to get precise line and variable info. Also glibc has to be compiled with -O, which makes debug a challenge. Will -Og help bintils and glibc debug? H.J.
