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RE: [PATCHv2, MIPS] Add support for O32 FPXX and program header based ABI information
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Matthew Fortune <Matthew dot Fortune at imgtec dot com>
- Cc: Will Newton <will dot newton at linaro dot org>, Andrew Pinski <pinskia at gmail dot com>, Richard Sandiford <rdsandiford at googlemail dot com>, Rich Fuhler <Rich dot Fuhler at imgtec dot com>, "macro at codesourcery dot com" <macro at codesourcery dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Fri, 16 May 2014 15:29:44 +0000
- Subject: RE: [PATCHv2, MIPS] Add support for O32 FPXX and program header based ABI information
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- References: <6D39441BF12EF246A7ABCE6654B0235352F38D at LEMAIL01 dot le dot imgtec dot org> <Pine dot LNX dot 4 dot 64 dot 1405141549300 dot 16785 at digraph dot polyomino dot org dot uk> <6D39441BF12EF246A7ABCE6654B0235352FF45 at LEMAIL01 dot le dot imgtec dot org> <Pine dot LNX dot 4 dot 64 dot 1405142119340 dot 21615 at digraph dot polyomino dot org dot uk> <6D39441BF12EF246A7ABCE6654B0235353041B at LEMAIL01 dot le dot imgtec dot org> <Pine dot LNX dot 4 dot 64 dot 1405151517380 dot 3155 at digraph dot polyomino dot org dot uk> <6D39441BF12EF246A7ABCE6654B02353531C1D at LEMAIL01 dot le dot imgtec dot org> <Pine dot LNX dot 4 dot 64 dot 1405152012500 dot 911 at digraph dot polyomino dot org dot uk> <6D39441BF12EF246A7ABCE6654B02353532EB3 at LEMAIL01 dot le dot imgtec dot org>
On Fri, 16 May 2014, Matthew Fortune wrote:
> I don't understand the use-case that would want a whole module (and/or
> subset of modules within one library) to freely deploy an ISA extension
> but have no overall marking to that extent. Such global enablement must be
It's the most basic, obvious, longstanding way of using an ISA feature
conditionally: compile different source files with different options and
then use "if" conditionals to choose between them. Support things like
IFUNCs and "target" attributes as well, sure, but first support the most
basic form that does not require any special language features at all.
For building source files with different options, in the IFUNC case, see
for example sysdeps/x86_64/fpu/multiarch/Makefile.
Design options to support that sort of basic usage before getting into
anything more complicated such as (optional) Solaris-style checks of
hardware support (which, as can be seen from recent gcc-patches
discussion, are a persistent cause of problems in the Solaris case;
people, and GCC testcases, don't expect such checks, so special cases are
needed for them all over the place).
--
Joseph S. Myers
joseph@codesourcery.com