[llvm] [AMDGPU] Add MovB64 subtarget feature (PR #196340)

[Matt Arsenault via llvm-commits]

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@@ -483,6 +483,10 @@ defm SBarrierLeaveImm : AMDGPUSubtargetFeature<"s-barrier-leave-imm",
   "s_barrier_leave takes an immediate operand"
 >;
 
+defm MovB64Inst : AMDGPUSubtargetFeature<"mov-b64-inst",
+  "Has mov_b64 instruction"
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arsenm wrote:

Should also add the v to the feature name 

https://github.com/llvm/llvm-project/pull/196340