Add UseRefIterator elimination test

Author: Ian Atol

test/compiler/irpasses.jl

@@ -831,3 +831,11 @@ let ci = code_typed(foo_cfg_empty, Tuple{Bool}, optimize=true)[1][1]
     @test length(ir.cfg.blocks) <= 2
     @test isa(ir.stmts[length(ir.stmts)][:inst], ReturnNode)
 end
+
+# Test that UseRefIterator gets SROA'd inside of new_to_regular (#44557)
+# expression and new_to_regular offset are arbitrary here, we just want to see the UseRefIterator erased
+let e = Expr(:call, Core.GlobalRef(Base, :arrayset), false, Core.SSAValue(4), Core.SSAValue(9), Core.SSAValue(8))
+    new_to_reg(expr) = Core.Compiler.new_to_regular(expr, 1)
+    @allocated new_to_reg(e) # warmup call
+    @test (@allocated new_to_reg(e)) == 0
+end