man: document --no-tag-primitive

[nit.git] / share / man / nitc.md

diff --git a/share/man/nitc.md b/share/man/nitc.md
index 75da7c8..b2e664a 100644 (file)
--- a/share/man/nitc.md
+++ b/share/man/nitc.md
@@ -115,11 +115,14 @@ See the documentation of these specific modules for details.
 
 `--log`
 :   Generate various log files.
-    Currently unused.
+
+    The tool will generate some files in the logging directory (see `--log-dir`).
+    These files are intended to the advanced user and the developers of the tools.
 
 `--log-dir`
 :   Directory where to generate log files.
-    Currently unused.
+
+    By default the directory is called `logs` in the working directory.
 
 
 `-h`, `-?`, `--help`
@@ -353,6 +356,16 @@ Usually you do not need them since they make the generated code slower.
 `--no-shortcut-equal`
 :   Always call == in a polymorphic way.
 
+`--no-tag-primitive`
+:   Use only boxes for primitive types.
+
+The separate compiler uses tagged values to encode common primitive types like Int, Bool and Char.
+This option disables tags and forces such primitive values to be boxed.
+The drawback is that each boxing costs a memory allocation thus increases the amount of work for the garbage collector.
+
+However, in some cases, it is possible that this option improves performance since the absence of tags simplify the implementation
+of OO mechanisms like method calls or equality tests.
+
 `--no-inline-intern`
 :   Do not inline call to intern methods.