Move documentation of additional system tasks from quirks to extensions.

Documentation/usage/icarus_verilog_extensions.rst

@@ -10,6 +10,52 @@ behavior of Icarus Verilog, made available as a tool debugging aid.
 Built-in System Functions
 -------------------------
 
+System Tasks
+------------
+
+These are system tasks that are unique to Icarus Verilog. Don't use any of
+these if you want to keep your code portable across other Verilog compilers.
+
+``$readmempath``
+^^^^^^^^^^^^^^^^
+
+The ``$readmemb`` and ``$readmemh`` system tasks read text files that contain
+data values to populate memories. Normally, those files are found in a current
+working directory. The ``$readmempath()`` system task can be used to create a
+search path for those files. For example:
+
+.. code-block:: verilog
+
+  reg [7:0] mem [0:7];
+  initial begin
+    $readmemh("datafile.txt", mem);
+  end
+
+This assumes that "datafile.txt" is in the current working directory where
+the ``vvp`` command is running. But with the ``$readmempath``, one can specify
+a search path:
+
+.. code-block:: verilog
+
+  reg [7:0] mem [0:7];
+  initial begin
+    $readmempath(".:alternative:/global/defaults");
+    $readmemh("datafile.txt", mem);
+  end
+
+In this example, "datafile.txt" is searched for in each of the directories
+in the above list (separated by ":" characters). The first located instance
+is the one that is used. So for example, if "./datafile.txt" exists, then it
+is read instead of "/global/defaults/datafile.txt" even if the latter exists.
+
+``$finish_and_return(code)``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This task operates the same as the ``$finish`` system task, but adds the
+feature of specifying an exit code for the interpreter. This can be useful in
+automated test environments to indicate whether the simulation finished with
+or without errors.
+
 Extended Verilog Data Types
 ---------------------------
 

Documentation/usage/icarus_verilog_quirks.rst

@@ -9,52 +9,6 @@ standard, or from other implementations.
 This is NOT AN EXHAUSTIVE LIST. If something is missing from this list, let us
 know and we can add documentation.
 
-System Tasks - Unique to Icarus Verilog
----------------------------------------
-
-These are system tasks that are unique to Icarus Verilog. Don't use any of
-these if you want to keep your code portable across other Verilog compilers.
-
-``$readmempath``
-^^^^^^^^^^^^^^^^
-
-The ``$readmemb`` and ``$readmemh`` system tasks read text files that contain
-data values to populate memories. Normally, those files are found in a current
-working directory. The ``$readmempath()`` system task can be used to create a
-search path for those files. For example:
-
-.. code-block:: verilog
-
-  reg [7:0] mem [0:7];
-  initial begin
-    $readmemh("datafile.txt", mem);
-  end
-
-This assumes that "datafile.txt" is in the current working directory where
-the ``vvp`` command is running. But with the ``$readmempath``, one can specify
-a search path:
-
-.. code-block:: verilog
-
-  reg [7:0] mem [0:7];
-  initial begin
-    $readmempath(".:alternative:/global/defaults");
-    $readmemh("datafile.txt", mem);
-  end
-
-In this example, "datafile.txt" is searched for in each of the directories
-in the above list (separated by ":" characters). The first located instance
-is the one that is used. So for example, if "./datafile.txt" exists, then it
-is read instead of "/global/defaults/datafile.txt" even if the latter exists.
-
-``$finish_and_return(code)``
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-This task operates the same as the ``$finish`` system task, but adds the
-feature of specifying an exit code for the interpreter. This can be useful in
-automated test environments to indicate whether the simulation finished with
-or without errors.
-
 Unsized Numeric Constants are Not Limited to 32 Bits
 ----------------------------------------------------