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Re: [Qemu-devel] [RFC PATCH] fpu: add compile time check for old glibc/l
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From: |
Richard Henderson |
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Subject: |
Re: [Qemu-devel] [RFC PATCH] fpu: add compile time check for old glibc/libm and fma |
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Date: |
Fri, 21 Dec 2018 14:01:02 -0800 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 |
On 12/21/18 11:30 AM, Emilio G. Cota wrote:
> + ua.s = 0x0020000000000001;
> + ub.s = 0x3ca0000000000000;
> + uc.s = 0x0020000000000000;
> + ur.h = fma(ua.h, ub.h, uc.h);
> + if (ur.s != 0x0020000000000001) {
Forgot your ull's, but otherwise ok.
In email to Alex, I did wonder if we should check for fma hardware (at least on
x86). Without a hardware insn, the libm routine is probably no faster than
softmmu.
r~