[llvm] [RFC][WIP][AMDGPU] Use `bf16` instead of `i16` for bfloat (PR #80908)

[Stanislav Mekhanoshin via llvm-commits]

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@@ -2819,11 +2819,11 @@ def int_amdgcn_fdot2_f16_f16 :
 def int_amdgcn_fdot2_bf16_bf16 :
   ClangBuiltin<"__builtin_amdgcn_fdot2_bf16_bf16">,
   DefaultAttrsIntrinsic<
-    [llvm_i16_ty],   // %r
+    [llvm_bfloat_ty],   // %r
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rampitec wrote:

This is the change in the existing interface, it will break programs already using it. It also will break clang builtin.

You can get away with changing only instruction's profile to use BF16 and tweak pattern with casts to bf16.

https://github.com/llvm/llvm-project/pull/80908