On Friday 21 December 2007 3:16:33 pm Kostik Belousov wrote: > On Fri, Dec 21, 2007 at 10:11:24AM -0800, Bakul Shah wrote: > > Peter Jeremy <peterjer...@optushome.com.au> wrote: > > > On Wed, Dec 19, 2007 at 09:40:34PM -0800, Carl Shapiro wrote: > > > >The default setting of the x87 floating point control word on the i386 > > > >port is 0x127F. Among other things, this value sets the precision > > > >control to double precision. The default setting of the x87 floating > > > >point control word on the AMD64 is 0x37F. > > > ... > > > >It seems clear that the right thing to do is to set the floating point > > > >environment to the i386 default for i386 binaries. Is the current > > > >behavior intended? > > > > > > I believe this is an oversight. See the thread beginning > > > http://lists.freebsd.org/pipermail/freebsd-stable/2007-November/037947.html > > > > >From reading Bruce's last message in that thread, seems to me > > may be default for 64bit binaries should be the same as on > > i386. Anyone wanting different behavior can always call > > fpsetprec() etc. > > > > I think the fix is to change __INITIAL_FPUCW__ in > > /sys/amd64/include/fpu.h to 0x127F like on i386. > I think this shall be done for 32-bit processes only, or we get into > another ABI breaking nightmare.
How about something like this: (Carl, can you please test this?) http://www.FreeBSD.org/~jhb/patches/amd64_fpu_i386.patch --- //depot/vendor/freebsd/src/sys/amd64/amd64/fpu.c 2006/06/19 22:39:16 +++ //depot/user/jhb/acpipci/amd64/amd64/fpu.c 2009/01/26 21:47:49 @@ -391,6 +391,7 @@ { struct pcb *pcb; register_t s; + u_short control; if (PCPU_GET(fpcurthread) == curthread) { printf("fpudna: fpcurthread == curthread %d times\n", @@ -421,6 +422,10 @@ * explicitly load sanitized registers. */ fxrstor(&fpu_cleanstate); + if (pcb->pcb_flags & PCB_32BIT) { + control = __INITIAL_FPUCW_I386__; + fldcw(&control); + } pcb->pcb_flags |= PCB_FPUINITDONE; } else fxrstor(&pcb->pcb_save); --- //depot/vendor/freebsd/src/sys/amd64/include/fpu.h 2004/04/05 21:30:47 +++ //depot/user/jhb/acpipci/amd64/include/fpu.h 2009/01/26 21:47:49 @@ -92,6 +92,7 @@ * SSE2 based math. For FreeBSD/amd64, we go with the default settings. */ #define __INITIAL_FPUCW__ 0x037F +#define __INITIAL_FPUCW_I386__ 0x127F #define __INITIAL_MXCSR__ 0x1F80 #define __INITIAL_MXCSR_MASK__ 0xFFBF -- John Baldwin _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
