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A comment on LLVM Clang 12 Merges Support For x86_64 Microarchitecture Levels. Parent comment

Re:LLVM Clang 12 Merges Support For x86_64 Microarchitecture... by kevincox on Monday November 09, 2020 @08:33AM (#25034593)
I think it would have been even easier to understand if they used the launch year of the architecture. Of course you may need a finer number (include the month or just a count if there are multiple launches in a year?) but I think it is worth it to get a rough idea of how old something is without finding a lookup table.
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Re:LLVM Clang 12 Merges Support For x86_64 Microarchitecture... by dragontamer on Monday November 09, 2020 @12:12PM (#25036961)
The details of chip releases is more complicated than just a numerical year.

FMA4 extensions on Bulldozer are no longer supported, so a 2012-era CPU supports FMA4, but 2018-era Zen processors do NOT support FMA4.

Xeon Phi supported a whole slew of AVX512 stuff that no other chip will ever support. Intel experimented with some instructions, and decided against them moving forward.

The point of a "vague" number, like "v3" is just to provide a general idea. Its purposefully vague, because the details are simply too messy to keep track of.

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Re:LLVM Clang 12 Merges Support For x86_64 Microarchitecture... by kevincox on Monday November 09, 2020 @12:37PM (#25037258)
I never suggested that year should be precise. I just think it is useful to use year as a vague number instead of something completely arbitrary. I think the only real downside is if people assume too much from that number.

> FMA4 extensions on Bulldozer are no longer supported, so a 2012-era CPU supports FMA4, but 2018-era Zen processors do NOT support FMA4.

I don't see how this is relevant. Isn't this the same problem that v4 supports something that v9 doesn't?

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