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Diffstat (limited to 'lib/hipe/doc')
| -rw-r--r-- | lib/hipe/doc/src/hipe_app.xml | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/lib/hipe/doc/src/hipe_app.xml b/lib/hipe/doc/src/hipe_app.xml index e489d155c3..0f8511eb00 100644 --- a/lib/hipe/doc/src/hipe_app.xml +++ b/lib/hipe/doc/src/hipe_app.xml @@ -47,6 +47,79 @@ Details on HiPE compiler options are given by <c>hipe:help_options()</c>.</p> </description> <section> + <title>Feature Limitations</title> + <p> + The HiPE compiler is in general compliant with the normal BEAM compiler, + with respect to semantic behavior. There are however features in the BEAM compiler + and the runtime system that have limited or no support for HiPE compiled modules. + </p> + <taglist> + <tag>Stack traces</tag> + <item><p>Stack traces returned from <seealso marker="erts:erlang#get_stacktrace/0"> + <c>erlang:get_stacktrace/0</c></seealso> or as part of <c>'EXIT'</c> terms + can look incomplete if HiPE compiled functions are involved. Typically a stack trace + will contain only BEAM compiled functions or only HiPE compiled functions, depending + on where the exception was raised.</p> + <p>Source code line numbers in stack traces are also not supported by HiPE compiled functions.</p> + </item> + + <tag>Tracing</tag> + <item><p>Modules compiled with HiPE have very limited support for runtime tracing + using <seealso marker="erts:erlang#trace_pattern/3"><c>erlang:trace_pattern/3</c></seealso>.</p> + </item> + + <tag>NIFs</tag> + <item><p>Modules compiled with HiPE can not call <seealso marker="erts:erlang#load_nif-2"> + <c>erlang:load_nif/2</c></seealso> to load NIFs.</p> + </item> + + <tag>-on_load</tag> + <item><p>Modules compiled with HiPE can not use + <seealso marker="doc/reference_manual:code_loading#on_load"><c>-on_load()</c></seealso> + directives.</p> + </item> + </taglist> + + </section> + <section> + <title>Performance Limitations</title> + <p> + The HiPE compiler does in general produce faster code than the + BEAM compiler. There are however some situation when HiPE + compiled code will perform worse than BEAM code. + </p> + <taglist> + <tag>Mode switches</tag> + <item><p>Every time a process changes from executing code in a + HiPE compiled module to a BEAM compiled module (or vice versa), + it will do a mode switch. This involves a certain amount of + CPU overhead which can have a negative net impact if the + process is switching back and forth without getting enough done in + each mode.</p> + </item> + + <tag>Optimization for <c>receive</c> with unique references</tag> + <item><p>The BEAM compiler can do an optimization when + a <c>receive</c> statement is <em>only</em> waiting for messages + containing a reference created before the receive. All messages + that existed in the queue when the reference was created will be + bypassed, as they cannot possibly contain the reference. HiPE + does not implement this optimization.</p> + <p>An example of this is when + <c>gen_server:call()</c> waits for the reply message.</p> + </item> + + <tag>Unused list comprehensions</tag> + <item><p>List comprehensions used only for their side effects, + will be optimized by BEAM to not produce the unused result + list. This optimization is not done by HiPE.</p> + <pre> +_ = [io:format("~p~n",[N]) || N <- lists:seq(1,10)],</pre> + </item> + + </taglist> + </section> + <section> <title>SEE ALSO</title> <p> <seealso marker="stdlib:c">c(3)</seealso>, |