[clang] [Clang][AArch64] Add fp8 variants for untyped NEON intrinsics (PR #128019)

[Paul Walker via cfe-commits]

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@@ -5464,6 +5464,15 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
           Builder.CreateStore(errorValue, swiftErrorTemp);
         }
 
+        // Mfloat8 type is loaded as scalar type, but is treated as single
+        // vector type for other operations. We need to bitcast it to the vector
+        // type here.
+        if (auto *EltTy =
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paulwalker-arm wrote:

The underlying storage for `__mfp8` is an FPR and until we decide whether to use a dedicated target type, or LLVM gains an opaque 8-bit floating point type our only option is to represent it as an i8 vector type.

The reason for using `i8` was for some specific code reuse but as this PR showed, that reuse is not total and so I'd rather we just be honest and insert the relevant bitcasts when necessary.  This will put us in good stead if we decide to go the target type route.

https://github.com/llvm/llvm-project/pull/128019