[clang] [Clang][AArch64]Add FP8 ACLE macros implementation (PR #140591)

[Paul Walker via cfe-commits]

================
@@ -1046,6 +1082,29 @@ bool AArch64TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
       HasSVEB16B16 = true;
       HasSMEB16B16 = true;
     }
+
+    if (Feature == "+fp8")
+      HasFP8 = true;
+    if (Feature == "+fp8fma")
----------------
paulwalker-arm wrote:

I don't fully understand the effect of setting these bools and how the dependencies in `AArch64Features.td` correspond to setting the feature macros.  What I'm mainly after is consistency and so for the SME2 extensions you're setting `HasSME2` as well.  So I guess the question is why that is necessary?  If it's not, then perhaps the way to go is to remove those rather than adding the ones I suggest.

The most important part to verify is that all the feature macros a user would expect to be defined by a specific +feat are in fact defined.  If that is managed by `AArch64Features.td` then great, if not then that would explain why the key feature dependencies are duplicated here.

https://github.com/llvm/llvm-project/pull/140591