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Re: [Qemu-arm] [Qemu-devel] [RFC PATCH for 2.11 05/23] softfloat3c: init
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-arm] [Qemu-devel] [RFC PATCH for 2.11 05/23] softfloat3c: initial build machinery |
Date: |
Fri, 21 Jul 2017 15:25:34 +0200 |
User-agent: |
NeoMutt/20170113 (1.7.2) |
On 2017-07-21 10:32, Alex Bennée wrote:
>
> Richard Henderson <address@hidden> writes:
>
> > On 07/20/2017 05:04 AM, Alex Bennée wrote:
> >> +# so they can still be linked when needed. We build these files
> >> surpressing so of the normal CFLAGS.
> >
> > "surpressing so" -> "suppressing some"
> >
> > Do we gain any confidence for our still supported but less tested
> > 32-bit hosts (all of which do support a 64-bit type) by dropping the
> > FAST_INT64 distinction?
>
> I guess so. Certainly I can cross-compile aarch64-softmmu on armhf
> defining all the:
>
> softfloat3_fastint64="yes"
> softfloat3_fastdiv32to16="yes"
> softfloat3_fastdiv64to32="yes"
>
> without any issue. I guess it might mean our 32 bit guests might run
> slightly slower but none of our FP is fast anyway.
>
> There is also a slight intermingling in the build setup between the
> FASTINT64 and the specialisation even though there are for different
> things.
>
> The 8086 code basically makes NaN propagation match old x86 whereas SSE
> is the more recent and more IEEE like SSE behaviour. See section 5 of:
>
> http://www.jhauser.us/arithmetic/SoftFloat-3c/doc/SoftFloat-source.html
>
> I suspect what we should have here are specialisation for each of our
> guests. We do something similar in the softfloat2a code in it's
> specialise header. Maybe we should rename 8086-SSE to default and then
> create a specialisation for each guest that needs it?
For the sNaN is 0 or 1 specialisation we actually need to be able to
select this at runtime, as we have implemented it in the QEMU softfloat
version.
Aurelien
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
address@hidden http://www.aurel32.net
- [Qemu-arm] [RFC PATCH for 2.11 00/23] Implementing FP16 for ARMv8.2 using SoftFloat2a and 3c, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 01/23] softfloat: move existing softfloat2a into versioned directory, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 06/23] softfloat3c: silence compiler warning, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 07/23] softfloat3c: f16_to_f128M remove unused variable, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 10/23] target/arm/translate-a64.c: handle_3same_64 comment fix, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 05/23] softfloat3c: initial build machinery, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 08/23] target-aarch64: enable SoftFloat3 build for FP16, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 09/23] arm: introduce ARM_V8_FP16 feature bit, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 11/23] target/arm/translate-a64.c: AdvSIMD scalar 3 Same FP16 initial decode, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 13/23] target/arm/translate-a64.c: add FP16 FADD to AdvSIMD 3 Same, Alex Bennée, 2017/07/20
- [Qemu-arm] [RFC PATCH for 2.11 12/23] target/arm/translate-a64.c: add FP16 FAGCT to AdvSIMD 3 Same, Alex Bennée, 2017/07/20