Le Tuesday 09 June 2009 16:00:47 Michael Buesch, vous avez écrit : > On Monday 08 June 2009 21:35:05 matthieu castet wrote: > > Michael Buesch wrote: > > > On Sunday 07 June 2009 11:28:50 matthieu castet wrote: > > >> Hi, > > >> > > >> I wonder with openwrt for bcm47xx is not build with "-msoft-float". > > >> The cpu doesn't have fpu and the current floating code get emulated by > > >> the kernel emulator instead of using the gcc emulation support (that > > >> is cheaper because there is no kernel trap). > > > > > > Well, I guess on a typical bcm47xx setup there's hardly any application > > > that uses floating point math. > > > > note that dropbear seems to use some, but that not critical. > > > > > Does -msoft-float increase the binary/image size? If so, I'd > > > vote for _not_ adding -msoft-float. If it doesn't make a size > > > difference, we should probably add it. > > > > That shouldn't increase size of application that don't use float. > > I did a quick test with dropbear that contain very few float. > > Here are the results (sfloat means -msoft-float, sgcc mean > > -shared-libgcc) > > > > > > $size /tmp/dropbear* > > text data bss dec hex filename > > 226924 4252 1744 232920 38dd8 /tmp/dropbear > > 234719 4328 1744 240791 3ac97 /tmp/dropbear_sfloat > > 220781 4192 1744 226717 3759d /tmp/dropbear_sfloat_sgcc > > 219956 4152 1744 225852 3723c /tmp/dropbear_sgcc > > > > As you can see with a static libgcc the size of the softfloat binary > > increase (8k) because all float emulation code is duplicated in the > > binary. With a shared libgcc the softfloat binary is smaller, the > > increase size is less than 1k. > > > > I don't know the impact for whole binary. I should try to build a > > typical bcm47xx setup and see the impact. > > Ok. It still smells like we're trying to solve a problem that does not > exist. Is the performance of any app increased in real life?
We can still allow soft-float to be used in the toolchain, and keep the in-kernel FPU emulator for compatibility, but then we will loose some space. -- Best regards, Florian Fainelli Email : flor...@openwrt.org http://openwrt.org -------------------------------
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