On 22.04.2025 13:39, Andrew Cooper wrote: > Compilers estimate the size of an asm() block for inlining purposes. > > Constructs such as ALTERNATIVE appear large due to the metadata, depsite often > only being a handful of instructions. asm inline() overrides the estimation > to identify the block as being small. > > This has a substantial impact on inlining decisions, expected to be for the > better given that the compiler has a more accurate picture to work with. > > Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
So this is effectively a generalized version of https://lists.xen.org/archives/html/xen-devel/2022-08/msg00712.html with ... > --- a/xen/Kconfig > +++ b/xen/Kconfig > @@ -29,6 +29,10 @@ config LD_IS_GNU > config LD_IS_LLVM > def_bool $(success,$(LD) --version | head -n 1 | grep -q "^LLD") > > +config CC_HAS_ASM_INLINE > + # GCC >= 9, Clang >= 11 > + def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) > -x c - -c -o /dev/null) ... detection once again done in Kconfig (only). I don't think I had any feedback there; I'm hence having a hard time seeing why I should now like this any better than mine was liked. In any event it's clearly increasingly necessary that we finally get the detection aspect settled. Jan
