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Re: [Ada] Generate Machine, Model and Rounding FP attributes in line
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Arnaud Charlet <charlet at adacore dot com>
- Cc: <gcc-patches at gcc dot gnu dot org>, Eric Botcazou <ebotcazou at adacore dot com>
- Date: Fri, 1 Aug 2014 15:47:48 +0000
- Subject: Re: [Ada] Generate Machine, Model and Rounding FP attributes in line
- Authentication-results: sourceware.org; auth=none
- References: <20140801092417 dot GA24621 at adacore dot com>
On Fri, 1 Aug 2014, Arnaud Charlet wrote:
> This change makes it so that the Machine, Model and Rounding FP attributes
> are generated in line by the compiler (in conjunction with a conversion to
> an integer type for the third) and optimized on architectures that do not
> make use of internal extended precision in the FPU.
Using TARGET_FLT_EVAL_METHOD would be better than basing this on examining
the machine modes (after all, on x86_64, you have XFmode but use of SSE
means there are no excess previous issues; likewise, ia64 has XFmode but
proper floating-point operations for all modes, including the formatOf
operations that take wider operands and produce a narrower result without
double rounding).
Except that S/390 defines TARGET_FLT_EVAL_METHOD to 1 for historical
reasons (but doesn't, I think, actually have any excess precision issues
with the back end - excess precision would only really be used for C with
-fexcess-precision=standard), so strictly you'd need a different macro
that differs from TARGET_FLT_EVAL_METHOD only on S/390 (i.e., a macro that
describes what FLT_EVAL_METHOD is at back-end level rather than what it is
at C API level with -fexcess-precision=standard).
--
Joseph S. Myers
joseph@codesourcery.com