On Sat, May 21, 2022 at 2:04 AM Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> wrote: > > Add a new compilation option which speeds-up compilation time. > This can be useful when using static checker such as smatch or build-bots. > In such cases, the speed and quality of the generated code is not > important. > > Using -O0 would be even better, but unfortunately, building fails with > this option. Which is a tragedy. As with the Rust series, I'm not a fan of this (or CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3): https://lore.kernel.org/lkml/CAKwvOd=7QTUH69+ZbT7e8einvgcosTbDkyohmPaUBv6_y8RfrQ@xxxxxxxxxxxxxx/ These feel more like attempts to wrap every conceivable command line flag in a kconfig option, which makes me think of that meme from Jurassic Park: "your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should." Not a fan. I'd ask for measurements, but that would be a request for a "rock fetching quest" for something I still wouldn't be a fan of. > > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> > --- > Makefile | 5 ++++- > init/Kconfig | 8 ++++++++ > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index 1f8bef92868f..14467386f947 100644 > --- a/Makefile > +++ b/Makefile > @@ -817,7 +817,10 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) > KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) > KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) > > -ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE > +ifdef CONFIG_CC_OPTIMIZE_FOR_COMPILATION_SPEED > +KBUILD_CFLAGS += -O1 > +KBUILD_RUSTFLAGS_OPT_LEVEL_MAP := 1 > +else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE > KBUILD_CFLAGS += -O2 > KBUILD_RUSTFLAGS_OPT_LEVEL_MAP := 2 > else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 > diff --git a/init/Kconfig b/init/Kconfig > index a96776a9b080..3177a1830c9a 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1384,6 +1384,14 @@ choice > prompt "Compiler optimization level" > default CC_OPTIMIZE_FOR_PERFORMANCE > > +config CC_OPTIMIZE_FOR_COMPILATION_SPEED > + bool "Optimize for compilation speed (-O1)" > + help > + This option can be useful when running a static checker such as smatch > + or a build-bot. > + Compilation time is slighly faster than -O2 and it requires less s/slighly/slightly/ > + memory. > + > config CC_OPTIMIZE_FOR_PERFORMANCE > bool "Optimize for performance (-O2)" > help > -- > 2.34.1 > -- Thanks, ~Nick Desaulniers
