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-rw-r--r--erts/emulator/internal_doc/CountingInstructions.md53
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+Counting Instructions
+=====================
+
+Here is an example that shows how to count how many times each
+instruction is executed:
+
+ $ (cd erts/emulator && make icount)
+ MAKE icount
+ make[1]: Entering directory `/home/uabbgus/otp/erts/emulator'
+ .
+ .
+ .
+ make[1]: Leaving directory `/home/uabbgus/otp/erts/emulator'
+ $ cat t.erl
+ -module(t).
+ -compile([export_all,nowarn_export_all]).
+
+ count() ->
+ erts_debug:ic(fun benchmark/0).
+
+ benchmark() ->
+ %% Run dialyzer.
+ Root = code:root_dir(),
+ Wc1 = filename:join(Root, "lib/{kernel,stdlib}/ebin/*.beam"),
+ Wc2 = filename:join(Root, "erts/preloaded/ebin/*.beam"),
+ Files = filelib:wildcard(Wc1) ++ filelib:wildcard(Wc2),
+ Opts = [{analysis_type,plt_build},{files,Files},{get_warnings,true}],
+ dialyzer:run(Opts).
+ $ $ERL_TOP/bin/cerl -icount
+ Erlang/OTP 22 [RELEASE CANDIDATE 1] [erts-10.2.4] [source-ac0d451] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe] [instruction-counting]
+
+ Eshell V10.2.4 (abort with ^G)
+ 1> c(t).
+ {ok,t}
+ 2> t:count().
+ 0 badarg_j
+ 0 badmatch_x
+ 0 bs_add_jsstx
+ 0 bs_context_to_binary_x
+ .
+ .
+ .
+ 536461394 move_call_last_yfQ
+ 552405176 allocate_tt
+ 619920327 i_is_eq_exact_immed_frc
+ 636419163 is_nonempty_list_allocate_frtt
+ 641859278 i_get_tuple_element_xPx
+ 678196718 move_return_c
+ 786289914 is_tagged_tuple_frAa
+ 865826424 i_call_f
+ Total: 20728870321
+ []
+ 3>