Re: [Qemu-devel] qemu-2007-10-24 build error

["Edgar E. Iglesias" <edgar.iglesias@axis.com>]

On Wed, Oct 24, 2007 at 12:33:24PM +0200, J. Mayer wrote:
> On Wed, 2007-10-24 at 09:36 +0900, Hwang YunSong(?????????) wrote:
> > 
> > gcc32 -g -o qemu-system-cris vl.o osdep.o readline.o monitor.o pci.o
> > console.o loader.o isa_mmio.o cutils.o block.o block-raw.o block-cow.o
> > block-qcow.o aes.o block-vmdk.o block-cloop.o block-dmg.o
> > block-bochs.o block-vpc.o block-vvfat.o block-qcow2.o
> > block-parallels.o irq.o i2c.o smbus.o scsi-disk.o cdrom.o lsi53c895a.o
> > usb.o usb-hub.o usb-linux.o usb-hid.o usb-ohci.o usb-msd.o usb-wacom.o
> > eeprom93xx.o eepro100.o ne2000.o pcnet.o rtl8139.o etraxfs.o ptimer.o
> > etraxfs_timer.o etraxfs_ser.o gdbstub.o sdl.o x_keymap.o vnc.o d3des.o
> > slirp/cksum.o slirp/if.o slirp/ip_icmp.o slirp/ip_input.o
> > slirp/ip_output.o slirp/slirp.o slirp/mbuf.o slirp/misc.o slirp/sbuf.o
> > slirp/socket.o slirp/tcp_input.o slirp/tcp_output.o slirp/tcp_subr.o
> > slirp/tcp_timer.o slirp/udp.o slirp/bootp.o slirp/debug.o slirp/tftp.o
> > libqemu.a -lm -lz -lgnutls -L/usr/lib -lSDL -lpthread -lrt -lutil 
> > libqemu.a(helper.o): In function `do_interrupt': 
> > /usr/src/Haansoft/BUILD/qemu/target-cris/helper.c:137: undefined
> > reference to `__builtin_clz' 
> > libqemu.a(translate-op.o): In function `dyngen_code': 
> > /home/hys545/qemu/cris-softmmu/op.h:1566: undefined reference to
> > `__builtin_clz' 
> > libqemu.a(op.o): In function `op_lz_T0_T1': 
> > /usr/src/Haansoft/BUILD/qemu/target-cris/op.c:1009: undefined
> > reference to `__builtin_clz' 
> > collect2: ld returned 1 exit status 
> 
> It does not seem to be a good idea, imho, to use gcc builtins directly
> from micro-ops. But your compiler should implement __builtin_clz. As far

Hi,

I submitted a patch that at compile-time fallbacks to clz code without builtins. Do you see any additional issues with using the builtins?

I think the speed-up with GCC ports implementing fast builtin variants of operations like clz would be significant enough to justify their use but if there is disagreement I'll send in a new patch removing the builtin_clz alltogether.

Best regards


> as I can see, the 4.1.1 version I got (Gentoo distribution) has this
> builtin implemented, then there might be a problem in your gcc package.
> I used this little program to check the builtin presence and found no
> version from gcc 3.4.4 to gcc 4.2.2 without __builtin_clz implemented:
> 
> int a = 123456;
> 
> int main (void)
> {
>     int b;
> 
>     b = __builtin_clz(a);
> 
>     return b;
> }
> 
> Compiled with gcc-<version> -O2 -Wall -W -o /tmp/clz /tmp/ckz.c
> 
> [...]
> 
> -- 
> J. Mayer <l_indien@magic.fr>
> Never organized
> 
> 
> 

-- 
Edgar E. Iglesias
Axis Communications AB