Date: Thu, 1 Oct 2015 12:35:50 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Stefan Parvu <sparvu@kronometrix.org> Cc: Andrew Turner <andrew@fubar.geek.nz>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org> Subject: Re: compile kernel with hard float support Message-ID: <20151001093550.GQ11284@kib.kiev.ua> In-Reply-To: <560CFBCA.5010001@kronometrix.org> References: <560CF28F.4000908@kronometrix.org> <20151001101825.44341b74@bender> <560CFBCA.5010001@kronometrix.org>
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On Thu, Oct 01, 2015 at 12:24:26PM +0300, Stefan Parvu wrote: > > > No, armv6 is built with softfp. This means the compiler is free to use > > the VFP, but when passing floating-point data between functions it > > needs to copy this to the general-purpose registers. > > > > Even without this the helper functions detect the presence of the VFP > > unit and make use of this when available. > > right. Got it. Thanks for explanation. > > > > The kernel doesn't use any floating-point hardware, other than to > > enable and disable it in the VFP driver. As such it doesn't matter if > > you've built the kernel for hard-float or not, it will make no > > difference to the code generated. > > ok, I see. Ok this probable wont make any difference to my case. > Right. 10 x thanks. The issue, apparently, in the initialization of the VFS state. I do not quite understand why ARM is set to flush to zero. Both C and IEEE FP standard expect that denormals work. The following patch worked for me WRT perl t/opbasic/arith.t test 175 (perl git blead checkout). diff --git a/sys/arm/arm/vm_machdep.c b/sys/arm/arm/vm_machdep.c index 223ad96..895a14c 100644 --- a/sys/arm/arm/vm_machdep.c +++ b/sys/arm/arm/vm_machdep.c @@ -134,7 +134,7 @@ cpu_fork(register struct thread *td1, register struct proc *p2, pcb2->pcb_regs.sf_sp = STACKALIGN(td2->td_frame); pcb2->pcb_vfpcpu = -1; - pcb2->pcb_vfpstate.fpscr = VFPSCR_DN | VFPSCR_FZ; + pcb2->pcb_vfpstate.fpscr = VFPSCR_DN; tf = td2->td_frame; tf->tf_spsr &= ~PSR_C;
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