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Re: PowerPC IEEE 128-bit floating point: Where we are


I'm going to try and summarize the current state of 128-bit floating point on
the PowerPC here.

There are 2 switches that control long double support in the compiler, but
without supporting libraries, it isn't useful to users:

-mabi=ieeelongdouble vs. -mabi=ibmlongdouble:

	These switches control which 128-bit format to use.  If you use either
	switch, you get two warning messages (one from the gcc drive, one from
	the compiler proper).

-mlong-double-128 vs. -mlong-double 64

	These switches control whether long double is 128-bits (either ibm/ieee
	formats), or 64-bits.

AIX and Darwin hardwires the choice to -mabi=ibmlongdouble, and you cannot use
the switch to override things.  Linux and Freebsd set the default to
-mabi=ibmlongdouble.  Any PowerPC system that is not AIX, Darwin, Linux, nor
Freebsd appears to default to IEEE 128-bit (vxworks?).

In terms of places where TFmode is mentioned in GCC, it is the following files:

	predicates.md, rs6000.c, rs6000.h, rs6000.md, rs6000-modes.def, spe.md

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797


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