`have_bf16` always returns `false` on Nvidia Grace CPU (neoverse-v2) on Linux

[giordano]

Function have_bf16 always returns false on an Nvidia Grace CPU (Neoverse V2), despite the fact the bf16 extension is available. In particular, the function caller.hasFnAttribute("julia.hasbf16") at

julia/src/llvm-demote-float16.cpp

Lines 75 to 83 in e9a24d4

	static bool have_bf16(Function &caller, const Triple &TT) {
	if (caller.hasFnAttribute("julia.hasbf16")) {
	return true;
	}
	// there's no targets that fully support bfloat yet;,
	// AVX512BF16 only provides conversion and dot product instructions.
	return false;
	}

is always 0. I tried also to compile from source with GCC 13, as suggested by @gbaraldi, but to no avail. CC: @maleadt.

[giordano]

Returning true on aarch64 may not be correct according to #55417 (comment). Closing in favour of #55479, which would be a better outcome overall.