Date: Mon, 7 Apr 2003 17:33:32 -0700 From: Kris Kennaway <kris@obsecurity.org> To: Thomas Moestl <tmoestl@gmx.net> Cc: Kris Kennaway <kris@obsecurity.org> Subject: Re: assembler error in XFree86 snapshot Message-ID: <20030408003332.GA60864@rot13.obsecurity.org> In-Reply-To: <20030116201728.GA279@crow.dom2ip.de> References: <20030116072448.GA29468@rot13.obsecurity.org> <20030116201728.GA279@crow.dom2ip.de>
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On Thu, Jan 16, 2003 at 09:17:28PM +0100, Thomas Moestl wrote:
> On Wed, 2003/01/15 at 23:24:48 -0800, Kris Kennaway wrote:
> > I'm trying to compile anholt's XFree86 4.2.99 snapshot on sparc, and I
> > get the following error message:
> >=20
> > cc -c -O -pipe -ansi -Dasm=3D__asm -Wall -Wpointer-arith -Wundef -I=
/usr/tmp/XFree86-4-libraries-devel/work/xc -I/usr/tmp/XFree86-4-libraries-d=
evel/work/xc/exports/include -DCSRG_BASED -DFUNCPROTO=3D15 -DNARROWPROTO=
-DXTHREADS -D_REENTRANT -D_THREAD_SAFE -DXUSE_MTSAFE_API -DXNO_MTSAFE_PWD=
API -DMALLOC_0_RETURNS_NULL XRes.c
> > {standard input}: Assembler messages:
> > {standard input}:667: Error: relocation overflow
> > *** Error code 1
> >=20
> > line 667 of the .s file is:
> >=20
> > > .LL86:
> > > umul %o0, 4294967295, %o0
>=20
> This is a arguably a gcc bug. All (13-bit) immediate operands are
> sign-extended, even those to instructions which operate on unsigned
> values, so umul can handle a range of very small and a range of very
> large operands. gcc correctly recognizes that it can use an immediate
> here; however, it chooses to output it as an unsigned number and does
> not sign-extended it from 32 to 64 bit.
>=20
> All sign extensions for instructions are made to the full 64 bit
> however (even if umul only happens to use 32 of those), so when the
> assembler checks whether a value is representable as an immediate, it
> will check that the 64-bit sign extension of the immediate creates
> the desired value (in sparc64 mode), i.e. it doesn't ignore the upper
> 32 bits even if a particular instruction does not use them.
>=20
> One solution is to generate negative literals for immediates if we
> mean them to be sign-extended (which gcc does already for some other
> instructions). The attached patch implements this, I'm not sure it
> uses the best possible way to do this though, and it also needs a bit
> more testing.
*Ping*
Someone needs to take this up with the gcc developers so it can get fixed.
Kris
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