| Message ID | 2802721.Q9KnE9eNH4@wuerfel (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
On Wed, May 13, 2015 at 10:56:39PM +0200, Arnd Bergmann wrote: > Building the 842 code on 32-bit ARM currently results in this link > error: > > ERROR: "__aeabi_uldivmod" [lib/842/842_decompress.ko] undefined! > > 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. > > 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) Ugh, relying on inlining to work is fragile. I'm not against making this inline but please make it work even when it is out- of-line. Thanks,
On Wed, May 13, 2015 at 10:56:39PM +0200, Arnd Bergmann wrote: > Building the 842 code on 32-bit ARM currently results in this link > error: > > ERROR: "__aeabi_uldivmod" [lib/842/842_decompress.ko] undefined! > > 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. > > 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) This had better get a comment to say why this is done, to stop the "don't do static inline in a .c" brigade reverting this change.
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;
Building the 842 code on 32-bit ARM currently results in this link error: ERROR: "__aeabi_uldivmod" [lib/842/842_decompress.ko] undefined! 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. 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 -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html