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ziglang / zig

General-purpose programming language and toolchain for maintaining robust, optimal, and reusable software.
https://ziglang.org
MIT License
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rename "i386" to "x86" #4663

Closed andrewrk closed 1 year ago

andrewrk commented 4 years ago

The baseline value we use for "i386" is currently a pentium4 cpu model, which is, I believe i686. I think it would be more correct to use "x86" rather than "i386" for this CPU architecture.

https://github.com/ziglang/zig/blob/80ff549e2602ecfc4eaf9ade0108e1779dff1874/lib/std/target.zig#L947

Sobeston commented 4 years ago

i386 is short for 80386 (1985). Pentium 4 (2000) all support MMX, SSE, SSE2. x86.cpu.pentium4 is listed as supporting SSE2 for example, which was not present in i386.

So yes, .i386 => &x86.cpu.pentium4 is not technically correct.

i686 (meaning P6 architecture, 1995) did not have SSE2, so we are targeting something slightly newer than both i386 and i686.

I'm in favour of calling the baseline cpu model x86, and just documenting that it's based off some specific intel micro architecture. edit: this is because pentium 4 was branding which contained many micro architectures - specifying Willamette, Northwood etc would be better.

Mouvedia commented 4 years ago

i686 first incarnation was the Pentium Pro which lacked the MMX instruction set. All pentium 4 supported MMX, SSE, SSE2; starting with the Prescott core they supported SSE3 as well.

_i686, pentiumpro_ Intel PentiumPro CPU.

_pentium4, pentium4m_ Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.

_prescott_ Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction set support.

pixelherodev commented 4 years ago

Shouldn't this be labeled arch-x86 then? ;)

Mouvedia commented 4 years ago

related: #4371

daurnimator commented 4 years ago

x86 is general accepted to cover all the *86 processors, including e.g. the 8086 and 80286 which are 16bit. I think what we want is more formally known as "IA-32" of which the 386 was the first.

jayschwa commented 4 years ago

x86 is general accepted to cover all the *86 processors, including e.g. the 8086 and 80286 which are 16bit. I think what we want is more formally known as "IA-32" of which the 386 was the first.

I agree with this suggestion from a technical correctness standpoint, but I disagree that "x86", as it is commonly used in the wild, implies support for 286 and below.

Mouvedia commented 4 years ago

IMHO it's either

.i686 => &x86.cpu.pentiumpro, which has the NOPL instruction

Intel did not document the NOPL instruction for the i686, yet all their 686 processors happened to implement it

which would reject, for example, the AMD Geode LX as a i686.

or

.i686 => &x86.cpu.i686,

which doesn't:

https://github.com/ziglang/zig/blob/0833c8d06ba9a467bb8449cbca2ba6f43d218c32/lib/std/target/x86.zig#L1835-L1844