[clang] [llvm] [llvm][AArch64] Support -mcpu=apple-m4 (PR #95478)

[Jon Roelofs via cfe-commits]

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@@ -521,7 +521,14 @@ inline constexpr CpuInfo CpuInfos[] = {
      AArch64::ExtensionBitset({AArch64::AEK_AES, AArch64::AEK_SHA2,
                                AArch64::AEK_SHA3, AArch64::AEK_FP16,
                                AArch64::AEK_FP16FML})},
-
+    // Technically apple-m4 is ARMv9.2a, but a quirk of LLVM defines v9.0 as
+    // requiring SVE, which is optional according to the Arm ARM and not
+    // supported by the core. ARMv8.7a is the next closest choice.
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jroelofs wrote:

Let's do that as a separate change _after_ this one.  That order will ensure this is still correct (as it can be) even after the revert, without the author of the revert having to think about this.

https://github.com/llvm/llvm-project/pull/95478