AMDGPU: Make llvm.amdgcn.endpgm convergent (#74555)

I don't believe this makes any practical difference.

Fixes #64013

Author: arsenm

llvm/include/llvm/IR/IntrinsicsAMDGPU.td

@@ -2105,7 +2105,8 @@ def int_amdgcn_wqm_vote : Intrinsic<[llvm_i1_ty],
 def int_amdgcn_kill : Intrinsic<[], [llvm_i1_ty], [IntrNoCallback, IntrNoFree]>;
 
 def int_amdgcn_endpgm : ClangBuiltin<"__builtin_amdgcn_endpgm">,
-  Intrinsic<[], [], [IntrNoReturn, IntrCold, IntrNoMem, IntrHasSideEffects, IntrNoCallback, IntrNoFree]
+  Intrinsic<[], [], [IntrNoReturn, IntrCold, IntrNoMem, IntrHasSideEffects, IntrConvergent,
+                     IntrNoCallback, IntrNoFree]
 >;
 
 // If false, mark all active lanes as helper lanes until the end of program.