From d231efe023a4a22ee2845ff6da3d3e1a733e433b Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Thu, 2 Nov 2017 20:35:11 +0100 Subject: hipe: Add doc sections about limitations --- lib/hipe/doc/src/hipe_app.xml | 73 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) (limited to 'lib/hipe') 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 @@ -46,6 +46,79 @@

For on-line help in the Erlang shell, call hipe:help(). Details on HiPE compiler options are given by hipe:help_options().

+
+ Feature Limitations +

+ 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. +

+ + Stack traces +

Stack traces returned from + erlang:get_stacktrace/0 or as part of 'EXIT' 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.

+

Source code line numbers in stack traces are also not supported by HiPE compiled functions.

+ + + Tracing +

Modules compiled with HiPE have very limited support for runtime tracing + using erlang:trace_pattern/3.

+ + + NIFs +

Modules compiled with HiPE can not call + erlang:load_nif/2 to load NIFs.

+ + + -on_load +

Modules compiled with HiPE can not use + -on_load() + directives.

+ + + +
+
+ Performance Limitations +

+ 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. +

+ + Mode switches +

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.

+ + + Optimization for receive with unique references +

The BEAM compiler can do an optimization when + a receive statement is only 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.

+

An example of this is when + gen_server:call() waits for the reply message.

+ + + Unused list comprehensions +

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.

+ 
+_ = [io:format("~p~n",[N]) || N <- lists:seq(1,10)],
+ + + +
SEE ALSO

-- cgit v1.2.3 From 987d6e240c0c80ccb4b3fa565ce22a6b29fc58cf Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Fri, 3 Nov 2017 17:51:01 +0100 Subject: Removed "unused list comprehensions" which don't seem to be true. --- lib/hipe/doc/src/hipe_app.xml | 8 -------- 1 file changed, 8 deletions(-) (limited to 'lib/hipe') diff --git a/lib/hipe/doc/src/hipe_app.xml b/lib/hipe/doc/src/hipe_app.xml index 0f8511eb00..7d22a014a0 100644 --- a/lib/hipe/doc/src/hipe_app.xml +++ b/lib/hipe/doc/src/hipe_app.xml @@ -109,14 +109,6 @@ gen_server:call() waits for the reply message.

- Unused list comprehensions -

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.

- 
-_ = [io:format("~p~n",[N]) || N <- lists:seq(1,10)],
- -
-- cgit v1.2.3 From b87b18e4cf6f94060d13e2aa2b9f7f008383ef20 Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Mon, 6 Nov 2017 19:57:15 +0100 Subject: Clearify call trace limitations. --- lib/hipe/doc/src/hipe_app.xml | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'lib/hipe') diff --git a/lib/hipe/doc/src/hipe_app.xml b/lib/hipe/doc/src/hipe_app.xml index 7d22a014a0..9299c6d73f 100644 --- a/lib/hipe/doc/src/hipe_app.xml +++ b/lib/hipe/doc/src/hipe_app.xml @@ -64,8 +64,9 @@ Tracing -

Modules compiled with HiPE have very limited support for runtime tracing - using erlang:trace_pattern/3.

+

Erlang call trace is not supported by HiPE. Calling + erlang:trace_pattern({M,F,A}, ...) + does not have any effect on HiPE compiled modules.

 NIFs -- cgit v1.2.3