Module Name:	pkgsrc
Committed By:	dmcmahill
Date:		Thu Jan 24 14:58:07 UTC 2002

Modified Files:
	pkgsrc/mk: defs.NetBSD.mk

Log Message:
For NetBSD/alpha versions >= 1.5V add -mieee to both CFLAGS and FFLAGS.
This will pass -mieee to those package which obey CFLAGS and FFLAGS.

paraphrasing an email from Ross:

The executive summary is: if i386 uses it (and
it does) then alpha should also, or some programs will SIGFPE out
on alpha when they don't on i386.

If anyone asks, the details are as follows:

The actual effect of -mieee is to put a software completion code
bit into every floating point instruction, and to put trap barrier
instructions in the code as necessary to ensure that traps are
delivered before branches or other instructions make it impossible
to trace backwards to the trapping op.

The code bits have little effect on the hardware, mainly what
happens is that when the hardware and palcode deliver a trap, they
tell the trap handler whether the faulting op had a completion
code.  If it did, the kernel is suppose to trace backwards, find
the op, and interpret it in SW, doing all the wacky ieee stuff that
most chips don't do, stuff like denormal arithmetic and the generation
of magic values (infinity, NaN) and the sticky flags.  We do all
that now except for a couple of truly obscure things that SoftFloat
didn't support and which I haven't yet added. (And these are things
that happen ONLY when you are taking overflow and underflow traps,
which no one has every really done AFAICT. If you have the default
behavior of gradual underflow and nontrapping infinity generation,
we do everything.)

This brings up the question of -mieee libraries, but that's not a
pkgsrc problem. (Except to the extent that I recommend that libraries
from pkgsrc, like everything else, also be compiled with -mieee.
And in the case of libraries, it might be worth individually
modifying the Makefile for the "not easy" case.)


To generate a diff of this commit:
cvs rdiff -r1.20 -r1.21 pkgsrc/mk/defs.NetBSD.mk

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.