Re: PROPOSAL: Extend inline asm syntax with size spec

Peter Zijlstra
2018-10-31T13:11:31Z

On Wed, Oct 31, 2018 at 01:55:26PM +0100, Peter Zijlstra wrote:
> On Sat, Oct 13, 2018 at 09:33:35PM +0200, Borislav Petkov wrote:
> > Ok,
> >
> > with Segher's help I've been playing with his patch ontop of bleeding
> > edge gcc 9 and here are my observations. Please double-check me for
> > booboos so that they can be addressed while there's time.
> >
> > So here's what I see ontop of 4.19-rc7:
> >
> > First marked the alternative asm() as inline and undeffed the "inline"
> > keyword. I need to do that because of the funky games we do with
> > "inline" redefinitions in include/linux/compiler_types.h.
> >
> > And Segher hinted at either doing:
> >
> > asm volatile inline(...
> >
> > or
> >
> > asm volatile __inline__(...
> >
> > but both "inline" variants are defined as macros in that file.
> >
> > Which means we either need to #undef inline before using it in asm() or
> > come up with something cleverer.
>
> # git grep -e "\<__inline__\>" | wc -l
> 488
> # git grep -e "\<__inline\>" | wc -l
> 56
> # git grep -e "\<inline\>" | wc -l
> 69598
>
> And we already have scripts/checkpatch.pl:
>
> # Check for __inline__ and __inline, prefer inline
>
> Which suggests we do:
>
> git grep -l "\<__inline\(\|__\)\>" | while read file
> do
> sed -i -e 's/\<__inline\(\|__\)\>/inline/g' $file
> done
>
> and get it over with.
>
>
> Anyway, with the below patch, I get:
>
> text data bss dec hex filename
> 17385183 5064780 1953892 24403855 1745f8f defconfig-build/vmlinux
> 17385678 5064780 1953892 24404350 174617e defconfig-build/vmlinux

17387603 5065468 1953892 24406963 1746bb3 defconfig-build/vmlinux

If I do an additional:

git grep -l "asm volatile" | while read file
do
sed -i -e 's/asm volatile/asm_volatile/g' $file
done

on the tree...

No changes for:

-#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
+#define asm_volatile_goto(x...) do { asm __inline__ goto (x); asm (""); } while (0)

I suppose all our goto's are small now (my tree includes Nadav's patch
to static_cpu_has).