> Building the 842 code on 32-bit ARM currently results in this link
> error:
>
> ERROR: "__aeabi_uldivmod" [lib/842/842_decompress.ko] undefined!
Oops! Guess I should build/test on 32 bit more.
>
> The reason is that the __do_index function performs a 64-bit
> division by a power-of-two number, but it has no insight into
> the function arguments.
>
> By marking that function inline, the fsize argument is always
> known at the time that do_index is called, and the compiler is
> able to replace the extremely expensive 64-bit division with
> a cheap constant shift operation.
alternately, we know that fsize will always be less than 64 bits,
at most it's 4<<9 or 8<<8 (both == 1<<11). So we could just change
its type to u16.
diff --git a/lib/842/842_decompress.c b/lib/842/842_decompress.c
index 6b2b45aecde3..285bf6b6959c 100644
--- a/lib/842/842_decompress.c
+++ b/lib/842/842_decompress.c
@@ -169,7 +169,7 @@ static int do_data(struct sw842_param *p, u8 n)
return 0;
}
-static int __do_index(struct sw842_param *p, u8 size, u8 bits, u64 fsize)
+static int __do_index(struct sw842_param *p, u8 size, u8 bits, u16 fsize)
{
u64 index, offset, total = round_down(p->out - p->ostart, 8);
int ret;
Or, we could inline it and change the type to u16. In any case,
Acked-by: Dan Streetman <[email protected]>
>
> Aside from fixing that link error, this approach should also improve
> both code size and performance on 32-bit architectures significantly.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> Found while building arm32 allmodconfig with gcc-5.0
>
> diff --git a/lib/842/842_decompress.c b/lib/842/842_decompress.c
> index 6b2b45aecde3..285bf6b6959c 100644
> --- a/lib/842/842_decompress.c
> +++ b/lib/842/842_decompress.c
> @@ -169,7 +169,7 @@ static int do_data(struct sw842_param *p, u8 n)
> return 0;
> }
>
> -static int __do_index(struct sw842_param *p, u8 size, u8 bits, u64 fsize)
> +static inline int __do_index(struct sw842_param *p, u8 size, u8 bits, u64
> fsize)
> {
> u64 index, offset, total = round_down(p->out - p->ostart, 8);
> int ret;
>
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