ohav chochmah <philomath868@xxxxxxxxx> writes: > first, is momit-leaf-frame-pointer bad for debugging (in the way > fomit-frame-pointer can be)? It's not as bad. It may still trip up some debuggers. > if not, why is it disabled by default > even when optimizing (as -Q --help=target | grep omit reveals)? When optimizing on x86 or x86_64, -fomit-frame-pointer is the default anyhow. -fomit-frame-pointer essentially implies -momit-leaf-frame-pointer. > next, the manual mentions that fno-fat-lto-objects improves > compilation time over plain LTO, but requires the whole toolchain to > be aware of LTO and support plugins, which is why it's not (yet) the > default. how can I know for certain if the toolchain I'm using meets > the criteria (seems to be the case)? Use the most recent GNU binutils release. > similarly, mtls-dialect=gnu2 is better then the default gnu, "but it > may add compile- and run-time requirements that cannot be satisfied on > all systems." how can I test for them? Build a program with it and see. Basically your GNU binutils need to be fairly new and your glibc needs to be 2.9 or later. > is it true that mfpmath=sse can result in poor code when using glibc? > (maybe I shouldn't ask that here...) For x86_64 -mfpmath=sse is the default. > why is msse disabled by default even after march=native, while > msse[234], msse4.[12] and mssse3 are all enabled? Not sure--what makes you think this is the case? > isn't the CRC32 instruction part of sse4.2?, why is mcrc32 disabled by > default even when sse4.2 is enabled? It's not. Don't be confused by the fact that -msse4.2 does not automatically turn on -mcrc32. Everything that is available when using -mcrc32 is also available when using -msse4.2. Ian
