From: Joseph Myers <joseph@codesourcery.com>
To: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: "linux-snps-arc@lists.infradead.org"
<linux-snps-arc@lists.infradead.org>,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>
Subject: Re: [PATCH v4 07/15] ARC: hardware floating point support
Date: Fri, 27 Mar 2020 18:37:13 +0000 [thread overview]
Message-ID: <alpine.DEB.2.21.2003271834390.5132@digraph.polyomino.org.uk> (raw)
In-Reply-To: <7462f741-d7d8-57f2-0fe9-c21b4b2829eb@synopsys.com>
On Fri, 27 Mar 2020, Vineet Gupta via Libc-alpha wrote:
> > The bits to enable exception traps look like dynamic control mode bits to
> > me. In general fegetmode should only need to mask off bits on
> > architectures where the same register has both control and status bits,
> > not on architectures where those are separate registers and fegetmode /
> > fesetmode can work with the whole control register.
>
> Yeah, looking back into my old dev branch, that is how I did it initially, but
> then switched to current implementation to "make get/set mode functions
> inter-operate with get/set round" - although there was no inter-calling between
> the two. We can go back to that implementation as it seems slightly better in
> generated code, but I'm curious if it is wrong too....
fegetmode / fesetmode deal with the complete set of dynamic control modes,
not just rounding modes. I don't think any masking or shifting is needed
or appropriate in fegetmode / fesetmode.
> Is following pseudo-code correct for semantics ?
>
> fesetenv(env)
>
> if FE_DFL_ENV
> fpcr = _FPU_DEFAULT;
> fpsr = _FPU_FPSR_DEFAULT;
> else
> fpcr = envp->__fpcr;
> fpsr = envp->__fpsr;
>
> feupdateenv(env)
>
> if FE_DFL_ENV
> fpcr = _FPU_DEFAULT;
> fpsr = _FPU_FPSR_DEFAULT;
> else
> fpcr = envp->__fpcr;
> fpsr |= envp->__fpsr; <-- this is different
feupdateenv has to preserve the previously raised exceptions even in the
FE_DFL_ENV case. It's equivalent to
exc = fetestexcept (FE_ALL_EXCEPT);
fesetenv (envp);
feraiseexcept (exc);
> In some places I have following:
>
> if (((fpcr >> __FPU_RND_SHIFT) & FE_DOWNWARD) != round)
>
> So FE_DOWNWARD (0x3) is used as mask, is that OK or would you rather see
>
> #define __FPU_RND_MASK 0x3
I think it's cleanest to have a separate define for the mask.
--
Joseph S. Myers
joseph@codesourcery.com
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next prev parent reply other threads:[~2020-03-27 18:37 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 3:04 [PATCH v4 00/15] glibc port to ARC processors Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 01/15] ARC: add definitions to elf/elf.h Vineet Gupta
2020-03-26 1:37 ` Joseph Myers
2020-03-26 1:52 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 02/15] ARC: ABI Implementation Vineet Gupta
2020-03-26 1:52 ` Joseph Myers
2020-03-26 2:39 ` Vineet Gupta
2020-03-26 18:48 ` Joseph Myers
2020-03-27 0:37 ` Vineet Gupta
2020-03-27 23:33 ` Vineet Gupta
2020-03-27 23:35 ` Joseph Myers
2020-03-27 23:47 ` Vineet Gupta
2020-03-31 21:08 ` Big Endian support as multi-ABI (was Re: [PATCH v4 02/15] ARC: ABI Implementation) Vineet Gupta
2020-03-31 21:27 ` Joseph Myers
2020-03-31 21:35 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 03/15] ARC: startup and dynamic linking code Vineet Gupta
2020-03-26 1:55 ` Joseph Myers
2020-03-26 2:45 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 04/15] ARC: Thread Local Storage support Vineet Gupta
2020-03-26 1:57 ` Joseph Myers
2020-03-26 2:47 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 05/15] ARC: Atomics and Locking primitives Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 06/15] ARC: math soft float support Vineet Gupta
2020-03-26 1:59 ` Joseph Myers
2020-03-26 2:48 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 07/15] ARC: hardware floating point support Vineet Gupta
2020-03-26 2:06 ` Joseph Myers
2020-03-26 3:19 ` Vineet Gupta
2020-03-26 23:22 ` Joseph Myers
2020-03-27 1:50 ` Vineet Gupta
2020-03-27 18:37 ` Joseph Myers [this message]
2020-03-27 18:53 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 08/15] ARC: Linux Syscall Interface Vineet Gupta
2020-03-26 23:52 ` Joseph Myers
2020-03-27 4:34 ` Vineet Gupta
2020-03-27 18:38 ` Joseph Myers
2020-03-13 3:04 ` [PATCH v4 09/15] ARC: Linux ABI Vineet Gupta
2020-03-27 0:38 ` Joseph Myers
2020-03-27 4:45 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 10/15] ARC: Linux Startup and Dynamic Loading Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 11/15] ARC: ABI lists Vineet Gupta
2020-03-27 0:40 ` Joseph Myers
2020-03-27 4:36 ` Vineet Gupta
2020-03-27 18:39 ` Joseph Myers
2020-03-27 19:09 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 12/15] ARC: Update syscall-names.list for ARC specific syscalls Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 13/15] ARC: Build Infrastructure Vineet Gupta
2020-03-27 22:47 ` Joseph Myers
2020-03-28 6:42 ` Vineet Gupta
2020-03-31 22:02 ` Vineet Gupta
2020-03-31 22:48 ` Joseph Myers
2020-04-01 0:44 ` __syscall_error (was Re: [PATCH v4 13/15] ARC: Build Infrastructure) Vineet Gupta
2020-04-01 7:58 ` Andreas Schwab
2020-04-01 21:38 ` Vineet Gupta
2020-04-01 17:06 ` Joseph Myers
2020-04-02 0:00 ` Vineet Gupta
2020-04-02 8:50 ` Florian Weimer
2020-04-02 20:22 ` Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 14/15] build-many-glibcs.py: Enable ARC builds Vineet Gupta
2020-03-13 3:04 ` [PATCH v4 15/15] Documentation for ARC port Vineet Gupta
2020-03-27 22:49 ` Joseph Myers
2020-03-27 23:56 ` Vineet Gupta
2020-03-28 0:01 ` Joseph Myers
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