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A comment on Fans of a 2013 Japanese soccer game tracked down a bizarre floating point bug. Parent comment

Re:Fans of a 2013 Japanese soccer game tracked down a bizarr... by masklinn on Tuesday September 07, 2021 @11:16AM (#28445888)
The negated variant make sense compared to the original, it's really the definition of msub which is strange, I would expect msub to subtract the last operand from the multiplication, not the other way around. The AMD64 mnemonics actually encode this order e.g. VFMADD213PDy is 2 * 1 + 3 (ba + c) while VFMADD132PDy is 1 * 3 + 2 (ac+b).

Though apparently the Dolphin folks disagree either way and interpret nmadd as (nm)add, rather than n(madd).

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Re:Fans of a 2013 Japanese soccer game tracked down a bizarr... by pm215 on Tuesday September 07, 2021 @11:55AM (#28446265)
The Arm ARM says FNMADD is "Floating-point Negated fused Multiply-Add", so the position of the hyphens points strongly to "n(madd)" rather than "(nm)add".
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Re:Fans of a 2013 Japanese soccer game tracked down a bizarr... by a1369209993 on Tuesday September 07, 2021 @05:36PM (#28450270)
> ARM says FNMADD is "Floating-point Negated fused Multiply-Add", so the position of the hyphens points

Never mind the hyphens, what do they think a "Negated fused Multiply" is?

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