🚀 go-pugleaf

	In the Ardent titan, using the BIT fp chips, we supported on
the fly, fully pipelined rounding mode changes.  We did this by making
the change rounding mode action an instruction, rather than a register
write. This greatly facilitates interval arithmetic, intrinsics, and what
have you, as discussed to death in this thread.
	However, since the changing of rounding modes is a pipelined
instruction, rather than a register write, the operating system has to
start up the vector unit while in kernel mode, and insert an
instruction into the stream if it is necessary to change rounding
modes upon context switch. 
	Luckily A) you could read the current rounding mode from a
status register, and only insert this instruction if you needed to
switch, and B) most programs use round to nearest.

	-mac
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