[clang] [llvm] Remove 3dnow from X86TargetParser. (PR #99352)

[Freddy Ye via llvm-commits]

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@@ -175,8 +175,6 @@ X86_FEATURE_COMPAT(AVX512BF16,      "avx512bf16",            34)
 X86_FEATURE_COMPAT(AVX512VP2INTERSECT, "avx512vp2intersect", 35)
 // Below Features has some missings comparing to gcc, it's because gcc has some
 // not one-to-one mapped in llvm.
-X86_FEATURE_COMPAT(3DNOW,           "3dnow",                  0)
-X86_FEATURE       (3DNOWA,          "3dnowa")
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FreddyLeaf wrote:

Sorry, I realized even gcc removed, they will keep one blank here to keep backward compatibility. So two features are required.
according to this comment above the file: 
```
// We cannot re-adjust the position of X86_FEATURE_COMPAT at the whole list.

https://github.com/llvm/llvm-project/pull/99352