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Re: PowerPC IEEE 128-bit floating point: Where we are
- From: Michael Meissner <meissner at linux dot vnet dot ibm dot com>
- To: Michael Meissner <meissner at linux dot vnet dot ibm dot com>, gcc at gcc dot gnu dot org, dje dot gcc at gmail dot com, amodra at gmail dot com, rguenther at suse dot de, jakub at redhat dot com, segher at kernel dot crashing dot org, bergner at vnet dot ibm dot com, rdsandiford at googlemail dot com, pthaugen at us dot ibm dot com, wschmidt at linux dot vnet dot ibm dot com, Ulrich dot Weigand at de dot ibm dot com, stigge at antcom dot de, vmakarov at redhat dot com, andrewd at gentrack dot com, joseph at codesourcery dot com, sjmunroe at us dot ibm dot com, nathan at codesourcery dot com, paul at codesourcery dot com, jason at redhat dot com, stigge at debian dot org, doko at ubuntu dot com, steven at gcc dot gnu dot org, dominiq at lps dot ens dot fr, acsawdey at linux dot vnet dot ibm dot com, azanella at linux dot vnet dot ibm dot com
- Date: Fri, 30 May 2014 16:22:23 -0400
- Subject: Re: PowerPC IEEE 128-bit floating point: Where we are
- Authentication-results: sourceware.org; auth=none
- References: <20140530195816 dot GA28688 at ibm-tiger dot the-meissners dot org>
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: email@example.com, phone: +1 (978) 899-4797