RE: [PATCH] zlib: define get_unaligned16() only when used
From: Arnd Bergmann
> Sent: 24 November 2020 11:57
>
> On Tue, Nov 24, 2020 at 12:51 PM Christoph Hellwig wrote:
> > On Tue, Nov 24, 2020 at 12:08:40PM +0100, Jann Horn wrote:
> > > > Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> > > > pre-increment optimization"), get_unaligned16() is only used when
> > > > !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
> > > >
> > > > Hence, make CC=clang W=1 warns:
> > > >
> > > > lib/zlib_inflate/inffast.c:20:1:
> > > > warning: unused function 'get_unaligned16' [-Wunused-function]
> > > >
> > > > Define get_unaligned16() only when it is actually used.
> > > >
> > > > Signed-off-by: Lukas Bulwahn
> > >
> > > AFAICS a nicer option would be to "#include " and
> > > then use "get_unaligned", which should automatically do the right
> > > thing everywhere and remove the need for defining get_unaligned16()
> > > and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
> >
> > Yes, that is the right thing to do.
>
> It's possible that this didn't work when the code was originally added:
> The decompressor functions are called from the compressed boot path,
> which is a bit limited regarding which headers it can include, at least
> on some architectures.
>
> I would recommend test-building this for all architectures that include
> ../../../../lib/decompress_inflate.c from their boot code.
Plausibly it could include a different header that defined the required
items for those builds.
David
-
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UK
Registration No: 1397386 (Wales)
Re: [PATCH] zlib: define get_unaligned16() only when used
On Tue, Nov 24, 2020 at 12:56 PM Arnd Bergmann wrote:
>
> On Tue, Nov 24, 2020 at 12:51 PM Christoph Hellwig wrote:
> > On Tue, Nov 24, 2020 at 12:08:40PM +0100, Jann Horn wrote:
> > > > Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> > > > pre-increment optimization"), get_unaligned16() is only used when
> > > > !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
> > > >
> > > > Hence, make CC=clang W=1 warns:
> > > >
> > > > lib/zlib_inflate/inffast.c:20:1:
> > > > warning: unused function 'get_unaligned16' [-Wunused-function]
> > > >
> > > > Define get_unaligned16() only when it is actually used.
> > > >
> > > > Signed-off-by: Lukas Bulwahn
> > >
> > > AFAICS a nicer option would be to "#include " and
> > > then use "get_unaligned", which should automatically do the right
> > > thing everywhere and remove the need for defining get_unaligned16()
> > > and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
> >
> > Yes, that is the right thing to do.
>
> It's possible that this didn't work when the code was originally added:
> The decompressor functions are called from the compressed boot path,
> which is a bit limited regarding which headers it can include, at least
> on some architectures.
>
> I would recommend test-building this for all architectures that include
> ../../../../lib/decompress_inflate.c from their boot code.
>
Jann, Christoph, Arnd, thanks for the advice. I will start to look
into this immediately.
Lukas
Re: [PATCH] zlib: define get_unaligned16() only when used
On Tue, Nov 24, 2020 at 12:51 PM Christoph Hellwig wrote:
> On Tue, Nov 24, 2020 at 12:08:40PM +0100, Jann Horn wrote:
> > > Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> > > pre-increment optimization"), get_unaligned16() is only used when
> > > !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
> > >
> > > Hence, make CC=clang W=1 warns:
> > >
> > > lib/zlib_inflate/inffast.c:20:1:
> > > warning: unused function 'get_unaligned16' [-Wunused-function]
> > >
> > > Define get_unaligned16() only when it is actually used.
> > >
> > > Signed-off-by: Lukas Bulwahn
> >
> > AFAICS a nicer option would be to "#include " and
> > then use "get_unaligned", which should automatically do the right
> > thing everywhere and remove the need for defining get_unaligned16()
> > and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
>
> Yes, that is the right thing to do.
It's possible that this didn't work when the code was originally added:
The decompressor functions are called from the compressed boot path,
which is a bit limited regarding which headers it can include, at least
on some architectures.
I would recommend test-building this for all architectures that include
../../../../lib/decompress_inflate.c from their boot code.
Arnd
Re: [PATCH] zlib: define get_unaligned16() only when used
On Tue, Nov 24, 2020 at 12:08:40PM +0100, Jann Horn wrote:
> > Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> > pre-increment optimization"), get_unaligned16() is only used when
> > !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
> >
> > Hence, make CC=clang W=1 warns:
> >
> > lib/zlib_inflate/inffast.c:20:1:
> > warning: unused function 'get_unaligned16' [-Wunused-function]
> >
> > Define get_unaligned16() only when it is actually used.
> >
> > Signed-off-by: Lukas Bulwahn
>
> AFAICS a nicer option would be to "#include " and
> then use "get_unaligned", which should automatically do the right
> thing everywhere and remove the need for defining get_unaligned16()
> and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
Yes, that is the right thing to do.
Re: [PATCH] zlib: define get_unaligned16() only when used
On Tue, Nov 24, 2020 at 11:40 AM Lukas Bulwahn wrote:
> Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> pre-increment optimization"), get_unaligned16() is only used when
> !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
>
> Hence, make CC=clang W=1 warns:
>
> lib/zlib_inflate/inffast.c:20:1:
> warning: unused function 'get_unaligned16' [-Wunused-function]
>
> Define get_unaligned16() only when it is actually used.
>
> Signed-off-by: Lukas Bulwahn
AFAICS a nicer option would be to "#include " and
then use "get_unaligned", which should automatically do the right
thing everywhere and remove the need for defining get_unaligned16()
and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
[PATCH] zlib: define get_unaligned16() only when used
Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
pre-increment optimization"), get_unaligned16() is only used when
!CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
Hence, make CC=clang W=1 warns:
lib/zlib_inflate/inffast.c:20:1:
warning: unused function 'get_unaligned16' [-Wunused-function]
Define get_unaligned16() only when it is actually used.
Signed-off-by: Lukas Bulwahn
---
applies cleanly on current master and next-20201124
Jann, please ack.
Andrew, please pick this minor non-urgent clean-up patch.
lib/zlib_inflate/inffast.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/lib/zlib_inflate/inffast.c b/lib/zlib_inflate/inffast.c
index ed1f3df27260..ca66d9008228 100644
--- a/lib/zlib_inflate/inffast.c
+++ b/lib/zlib_inflate/inffast.c
@@ -15,7 +15,8 @@ union uu {
unsigned char b[2];
};
-/* Endian independed version */
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+/* Endian independent version */
static inline unsigned short
get_unaligned16(const unsigned short *p)
{
@@ -26,6 +27,7 @@ get_unaligned16(const unsigned short *p)
mm.b[1] = b[1];
return mm.us;
}
+#endif
/*
Decode literal, length, and distance codes and write out the resulting
--
2.17.1
