[llvm] [LLVM][NVPTX]Add BF16 vector instruction and fix lowering rules (PR #69415)

[Artem Belevich via llvm-commits]

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@@ -629,7 +657,7 @@ let hasSideEffects = false in {
                 ToType, ".bf16 \t$dst, $src;"), []>,
       Requires<!if(!eq(ToType, "f32"),
                    // bf16->f32 was introduced early.
-                   [hasPTX<71>, hasSM<80>],
+                   [hasPTX<70>, hasSM<80>],
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Artem-B wrote:

I vaguely recall that there were issues with PTX 7.0. I think ptxas didn't actually accept those instructions, despite the docs saying that it should.

This definitely needs double checking.

https://github.com/llvm/llvm-project/pull/69415