Improve getdict performance (#42057)

Co-authored-by: Ian Butterworth <i.r.butterworth@gmail.com>

Author: vchuravy

stdlib/Profile/src/Profile.jl

@@ -214,10 +214,14 @@ function retrieve()
 end
 
 function getdict(data::Vector{UInt})
-    # Lookup is expensive, so do it only once per ip.
-    udata = unique(data)
     dict = LineInfoDict()
-    for ip in udata
+    return getdict!(dict, data)
+end
+
+function getdict!(dict::LineInfoDict, data::Vector{UInt})
+    for ip in data
+        # Lookup is expensive, so do it only once per ip.
+        haskey(dict, UInt64(ip)) && continue
         st = lookup(convert(Ptr{Cvoid}, ip))
         # To correct line numbers for moving code, put it in the form expected by
         # Base.update_stackframes_callback[]