[llvm] [NVPTX] Improve support for {ex2,lg2}.approx (PR #120519)

[Alex MacLean via llvm-commits]

================
@@ -964,6 +964,10 @@ let TargetPrefix = "nvvm" in {
       DefaultAttrsIntrinsic<[llvm_half_ty], [llvm_half_ty], [IntrNoMem]>;
   def int_nvvm_ex2_approx_f16x2 :
       DefaultAttrsIntrinsic<[llvm_v2f16_ty], [llvm_v2f16_ty], [IntrNoMem]>;
+  def int_nvvm_ex2_approx_bf16 :
+      DefaultAttrsIntrinsic<[llvm_bfloat_ty], [llvm_bfloat_ty], [IntrNoMem]>;
+  def int_nvvm_ex2_approx_bf16x2 :
+      DefaultAttrsIntrinsic<[llvm_v2bf16_ty], [llvm_v2bf16_ty], [IntrNoMem]>;
----------------
AlexMaclean wrote:

Are these intrinsics different from `llvm.exp2` than? If not, we should probably remove and auto-upgrade them, not add new ones. 

https://github.com/llvm/llvm-project/pull/120519