Messages in this thread Patch in this message | | | From | Dan Streetman <> | Subject | Re: [PATCH] lib: fix 842 build on 32-bit architectures | Date | Wed, 13 May 2015 19:52:24 -0400 |
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> 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 <ddstreet@ieee.org>
> > 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 <arnd@arndb.de> > --- > 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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