Messages in this thread | | | Date | Mon, 22 Apr 2024 10:24:46 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH 1/1] arm64: optimize code duplication in arch_static_branch/_jump function |
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On Mon, Apr 22, 2024 at 02:38:53PM +0800, George Guo wrote: > From: George Guo <guodongtai@kylinos.cn> > > Extracted the jump table definition code from the arch_static_branch and > arch_static_branch_jump functions into a macro JUMP_TABLE_ENTRY to reduce > code duplication and improve readability.
The commit title says this is an optimization, but the commit message says this is a cleanup (and this clearly is not an optimization).
This seems to be copying what x86 did in commit:
e1aa35c4c4bc71e4 ("jump_label, x86: Factor out the __jump_table generation")
.. where the commit message is much clearer.
> > Signed-off-by: George Guo <guodongtai@kylinos.cn> > --- > arch/arm64/include/asm/jump_label.h | 19 +++++++++---------- > 1 file changed, 9 insertions(+), 10 deletions(-) > > diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h > index 6aafbb789991..69407b70821e 100644 > --- a/arch/arm64/include/asm/jump_label.h > +++ b/arch/arm64/include/asm/jump_label.h > @@ -15,16 +15,19 @@ > > #define JUMP_LABEL_NOP_SIZE AARCH64_INSN_SIZE > > +#define JUMP_TABLE_ENTRY \ > + ".pushsection __jump_table, \"aw\" \n\t" \ > + ".align 3 \n\t" \ > + ".long 1b - ., %l[l_yes] - . \n\t" \ > + ".quad %c0 - . \n\t" \ > + ".popsection \n\t" > + > static __always_inline bool arch_static_branch(struct static_key * const key, > const bool branch) > { > asm goto( > "1: nop \n\t" > - " .pushsection __jump_table, \"aw\" \n\t" > - " .align 3 \n\t" > - " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > - " .popsection \n\t" > + JUMP_TABLE_ENTRY > : : "i"(&((char *)key)[branch]) : : l_yes);
If we really need to factor this out, I'd prefer that the JUMP_TABLE_ENTRY() macro took the label and key as arguments, similar to what we do for _ASM_EXTABLE_*().
Mark.
> > return false; > @@ -37,11 +40,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke > { > asm goto( > "1: b %l[l_yes] \n\t" > - " .pushsection __jump_table, \"aw\" \n\t" > - " .align 3 \n\t" > - " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > - " .popsection \n\t" > + JUMP_TABLE_ENTRY > : : "i"(&((char *)key)[branch]) : : l_yes); > > return false; > -- > 2.34.1 > >
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