Working on extensions doc

Moved the last files out of the resources directory.
Some tidy up/reformatting of the extensions to allow literalincludes from `my_cmd.cc`.
Most (all?) of the getting started guidelines file is either in the quick guide section, or sections referenced by it.  Instead of including it verbatim, we'll instead just leave a reference to it but then jump straight into the quick guide.
Include an image for the absval generated module.  Still needs more surrounding text but it's good enough for now.

Also includes some other minor tidying, including removing the no longer used abc_01 code example.

docs/source/code_examples/extensions/Makefile

@@ -1,9 +1,11 @@
 PROGRAM_PREFIX :=
 
-YOSYS ?= ../../../$(PROGRAM_PREFIX)yosys
+YOSYS ?= ../../../../$(PROGRAM_PREFIX)yosys
 
 all: test0.log test1.log test2.log
 
+dots: test1.dot
+
 CXXFLAGS=$(shell $(YOSYS)-config --cxxflags)
 DATDIR=$(shell $(YOSYS)-config --datdir)
 
@@ -18,6 +20,9 @@ test1.log: my_cmd.so
 	$(YOSYS) -Ql test1.log_new -m ./my_cmd.so -p 'clean; test1; dump' absval_ref.v
 	mv test1.log_new test1.log
 
+test1.dot:
+	$(YOSYS) -m ./my_cmd.so -p 'test1; show -format dot -prefix test1'
+
 test2.log: my_cmd.so
 	$(YOSYS) -Ql test2.log_new -m ./my_cmd.so -p 'hierarchy -top test; test2' sigmap_test.v
 	mv test2.log_new test2.log

docs/source/code_examples/extensions/absval_ref.v

@@ -1,3 +1,3 @@
 module absval_ref(input signed [3:0] a, output [3:0] y);
-    assign y = a[3] ? -a : a;
+	assign y = a[3] ? -a : a;
 endmodule

docs/source/code_examples/extensions/my_cmd.cc

@@ -14,7 +14,7 @@ struct MyPass : public Pass {
 
         log("Modules in current design:\n");
         for (auto mod : design->modules())
-            log("  %s (%zd wires, %zd cells)\n", log_id(mod),
+            log("  %s (%d wires, %d cells)\n", log_id(mod),
                     GetSize(mod->wires()), GetSize(mod->cells()));
     }
 } MyPass;

docs/source/code_examples/extensions/sigmap_test.v

@@ -1,3 +1,3 @@
 module test(input a, output x, y);
-assign x = a, y = a;
+	assign x = a, y = a;
 endmodule

docs/source/code_examples/synth_flow/Makefile

@@ -3,7 +3,6 @@ TARGETS += proc_01 proc_02 proc_03
 TARGETS += opt_01 opt_02 opt_03 opt_04
 TARGETS += memory_01 memory_02
 TARGETS += techmap_01
-TARGETS += abc_01
 
 PROGRAM_PREFIX :=
 

docs/source/code_examples/synth_flow/abc_01.v

@@ -1,10 +0,0 @@
-module test(input clk, a, b, c,
-            output reg y);
-
-	reg [2:0] q1, q2;
-	always @(posedge clk) begin
-		q1 <= { a, b, c };
-		q2 <= q1;
-		y <= ^q2;
-	end
-endmodule

docs/source/code_examples/synth_flow/abc_01.ys

@@ -1,5 +0,0 @@
-read_verilog abc_01.v
-read_verilog -lib abc_01_cells.v
-hierarchy -check -top test
-proc; opt; techmap
-abc -dff -liberty abc_01_cells.lib;;

docs/source/code_examples/synth_flow/abc_01_cells.lib

@@ -1,54 +0,0 @@
-// test comment
-/* test comment */
-library(demo) {
-  cell(BUF) {
-    area: 6;
-    pin(A) { direction: input; }
-    pin(Y) { direction: output;
-              function: "A"; }
-  }
-  cell(NOT) {
-    area: 3;
-    pin(A) { direction: input; }
-    pin(Y) { direction: output;
-              function: "A'"; }
-  }
-  cell(NAND) {
-    area: 4;
-    pin(A) { direction: input; }
-    pin(B) { direction: input; }
-    pin(Y) { direction: output;
-             function: "(A*B)'"; }
-  }
-  cell(NOR) {
-    area: 4;
-    pin(A) { direction: input; }
-    pin(B) { direction: input; }
-    pin(Y) { direction: output;
-             function: "(A+B)'"; }
-  }
-  cell(DFF) {
-    area: 18;
-    ff(IQ, IQN) { clocked_on: C;
-                  next_state: D; }
-    pin(C) { direction: input;
-                 clock: true; }
-    pin(D) { direction: input; }
-    pin(Q) { direction: output;
-              function: "IQ"; }
-  }
-  cell(DFFSR) {
-    area: 18;
-    ff(IQ, IQN) { clocked_on: C;
-                  next_state: D;
-                      preset: S;
-                       clear: R; }
-    pin(C) { direction: input;
-                 clock: true; }
-    pin(D) { direction: input; }
-    pin(Q) { direction: output;
-              function: "IQ"; }
-    pin(S) { direction: input; }
-    pin(R) { direction: input; }
-  }
-}

docs/source/code_examples/synth_flow/abc_01_cells.v

@@ -1,40 +0,0 @@
-
-module BUF(A, Y);
-input A;
-output Y = A;
-endmodule
-
-module NOT(A, Y);
-input A;
-output Y = ~A;
-endmodule
-
-module NAND(A, B, Y);
-input A, B;
-output Y = ~(A & B);
-endmodule
-
-module NOR(A, B, Y);
-input A, B;
-output Y = ~(A | B);
-endmodule
-
-module DFF(C, D, Q);
-input C, D;
-output reg Q;
-always @(posedge C)
-	Q <= D;
-endmodule
-
-module DFFSR(C, D, Q, S, R);
-input C, D, S, R;
-output reg Q;
-always @(posedge C, posedge S, posedge R)
-	if (S)
-		Q <= 1'b1;
-	else if (R)
-		Q <= 1'b0;
-	else
-		Q <= D;
-endmodule
-

docs/source/using_yosys/yosys_flows.rst

@@ -278,7 +278,9 @@ Checking.
 Checking techmap
 ~~~~~~~~~~~~~~~~
 
-.. todo:: add/expand supporting text, reference no longer exists
+.. todo:: add/expand supporting text
+
+.. TODO:: reference no longer exists
 
 Remember the following example from :doc:`/getting_started/typical_phases`?
 

docs/source/yosys_internals/extending_yosys/extensions.rst

@@ -1,52 +1,25 @@
 Writing extensions
 ==================
 
+.. role:: yoscrypt(code)
+   :language: yoscrypt
+
 .. todo:: check text is coherent
 
 This chapter contains some bits and pieces of information about programming
 yosys extensions. Don't be afraid to ask questions on the YosysHQ Slack.
 
-Guidelines
-----------
+The `guidelines/` directory of the Yosys source code contains notes on various
+aspects of Yosys development. In particular, the files GettingStarted and
+CodingStyle may be of interest.
 
-The guidelines directory contains notes on various aspects of Yosys development.
-The files GettingStarted and CodingStyle may be of particular interest, and are
-reproduced here.
-
-.. literalinclude:: /temp/GettingStarted
-    :language: none
-    :caption: guidelines/GettingStarted
-
-.. literalinclude:: /temp/CodingStyle
-    :language: none
-    :caption: guidelines/CodingStyle
-
-The "stubsnets" example module
-------------------------------
-
-The following is the complete code of the "stubsnets" example module. It is
-included in the Yosys source distribution as
-``docs/source/code_examples/stubnets/stubnets.cc``.
-
-.. literalinclude:: /code_examples/stubnets/stubnets.cc
-    :language: c++
-    :linenos:
-    :caption: docs/source/code_examples/stubnets/stubnets.cc
-
-.. literalinclude:: /code_examples/stubnets/Makefile
-    :language: makefile
-    :linenos:
-    :caption: docs/source/code_examples/stubnets/Makefile
-
-.. literalinclude:: /code_examples/stubnets/test.v
-    :language: verilog
-    :linenos:
-    :caption: docs/source/code_examples/stubnets/test.v
+.. todo:: what's in guidelines/GettingStarted that's missing from the manual?
 
 Quick guide
 -----------
 
-See also: ``docs/resources/PRESENTATION_Prog/*``.
+Code examples from this section are included in the
+``docs/code_examples/extensions/`` directory of the Yosys source code.
 
 Program components and data formats
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -76,39 +49,90 @@ It is possible to only work on this simpler version:
 
 When trying to understand what a command does, creating a small test case to
 look at the output of :cmd:ref:`dump` and :cmd:ref:`show` before and after the
-command has been executed can be helpful.  The
-:doc:`/using_yosys/more_scripting/selections` document has more information on
-using these commands.
+command has been executed can be helpful.
+:doc:`/using_yosys/more_scripting/selections` has more information on using
+these commands.
+
+Creating a command
+~~~~~~~~~~~~~~~~~~
+
+.. todo:: add/expand supporting text
+
+Let's create a very simple test command which prints the arguments we called it
+with, and lists off the current design's modules.
+
+.. literalinclude:: /code_examples/extensions/my_cmd.cc
+   :language: c++
+   :lines: 1, 4, 6, 7-20
+   :caption: Example command :yoscrypt:`my_cmd` from ``my_cmd.cc``
+   
+Note that we are making a global instance of a class derived from
+``Yosys::Pass``, which we get by including ``kernel/yosys.h``.
+
+Compiling to a plugin
+~~~~~~~~~~~~~~~~~~~~~
+
+Yosys can be extended by adding additional C++ code to the Yosys code base, or
+by loading plugins into Yosys.  For maintainability it is generally recommended
+to create plugins.
+
+The following command compiles our example :yoscrypt:`my_cmd` to a Yosys plugin:
+
+.. code:: shell
+
+   yosys-config --exec --cxx --cxxflags --ldflags \
+   -o my_cmd.so -shared my_cmd.cc --ldlibs
+
+Or shorter:
+
+.. code:: shell
+
+   yosys-config --build my_cmd.so my_cmd.cc
+
+Running Yosys with the ``-m`` option allows the plugin to be used.  Here's a
+quick example that also uses the ``-p`` option to run :yoscrypt:`my_cmd foo
+bar`.
+
+.. code:: shell-session
+
+   $ yosys -m ./my_cmd.so -p 'my_cmd foo bar'
+
+   -- Running command `my_cmd foo bar' --
+   Arguments to my_cmd:
+     my_cmd
+     foo
+     bar
+   Modules in current design:
 
 Creating modules from scratch
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-.. todo:: add/expand supporting text, also use files in docs/resources/PRESENTATION_Prog
-
 Let's create the following module using the RTLIL API:
 
-.. literalinclude:: ../../../resources/PRESENTATION_Prog/absval_ref.v
-    :language: Verilog
-    :caption: docs/resources/PRESENTATION_Prog/absval_ref.v
+.. literalinclude:: /code_examples/extensions/absval_ref.v
+   :language: Verilog
+   :caption: absval_ref.v
 
-.. code:: C++
+We'll do the same as before and format it as a a ``Yosys::Pass``.
 
-    RTLIL::Module *module = new RTLIL::Module;
-    module->name = "\\absval";
+.. literalinclude:: /code_examples/extensions/my_cmd.cc
+   :language: c++
+   :lines: 23-47
+   :caption: :yoscrypt:`test1` - creating the absval module, from ``my_cmd.cc``
 
-    RTLIL::Wire *a = module->addWire("\\a", 4);
-    a->port_input = true;
-    a->port_id = 1;
+.. code:: shell-session
 
-    RTLIL::Wire *y = module->addWire("\\y", 4);
-    y->port_output = true;
-    y->port_id = 2;
+   $ yosys -m ./my_cmd.so -p 'test1' -Q
 
-    RTLIL::Wire *a_inv = module->addWire(NEW_ID, 4);
-    module->addNeg(NEW_ID, a, a_inv, true);
-    module->addMux(NEW_ID, a, a_inv, RTLIL::SigSpec(a, 1, 3), y);
+   -- Running command `test1' --
+   Name of this module: absval
 
-    module->fixup_ports();
+And if we look at the schematic for this new module we see the following:
+
+.. figure:: /_images/code_examples/extensions/test1.*
+   :class: width-helper
+
+   Output of ``yosys -m ./my_cmd.so -p 'test1; show'``
 
 Modifying modules
 ~~~~~~~~~~~~~~~~~
@@ -124,7 +148,6 @@ When modifying existing modules, stick to the following DOs and DON'Ts:
 - You can safely remove cells or change the ``connections`` property of a cell,
   but be careful when changing the size of the ``SigSpec`` connected to a cell
   port.
-
 - Use the ``SigMap`` helper class (see next section) when you need a unique
   handle for each signal bit.
 
@@ -133,13 +156,14 @@ Using the SigMap helper class
 
 Consider the following module:
 
-.. code:: Verilog
+.. literalinclude:: /code_examples/extensions/sigmap_test.v
+   :language: Verilog
+   :caption: sigmap_test.v
 
-    module test(input a, output x, y);
-        assign x = a, y = a;
-    endmodule
+In this case ``a``, ``x``, and ``y`` are all different names for the same
+signal. However:
 
-In this case ``a``, ``x``, and ``y`` are all different names for the same signal. However:
+.. todo:: use my_cmd.cc literalincludes
 
 .. code:: C++
 
@@ -148,7 +172,8 @@ In this case ``a``, ``x``, and ``y`` are all different names for the same signal
     log("%d %d %d\n", a == x, x == y, y == a); // will print "0 0 0"
 
 The ``SigMap`` helper class can be used to map all such aliasing signals to a
-unique signal from the group (usually the wire that is directly driven by a cell or port).
+unique signal from the group (usually the wire that is directly driven by a cell
+or port).
 
 .. code:: C++
 
@@ -159,7 +184,8 @@ unique signal from the group (usually the wire that is directly driven by a cell
 Printing log messages
 ~~~~~~~~~~~~~~~~~~~~~
 
-The ``log()`` function is a ``printf()``-like function that can be used to create log messages.
+The ``log()`` function is a ``printf()``-like function that can be used to
+create log messages.
 
 Use ``log_signal()`` to create a C-string for a SigSpec object:
 
@@ -206,53 +232,24 @@ Use ``log_cmd_error()`` to report a recoverable error:
 
 Use ``log_assert()`` and ``log_abort()`` instead of ``assert()`` and ``abort()``.
 
-Creating a command
-~~~~~~~~~~~~~~~~~~
+The "stubnets" example module
+------------------------------
 
-Simply create a global instance of a class derived from ``Pass`` to create
-a new yosys command:
+The following is the complete code of the "stubnets" example module. It is
+included in the Yosys source distribution as
+``docs/source/code_examples/stubnets/stubnets.cc``.
 
-.. code:: C++
+.. literalinclude:: /code_examples/stubnets/stubnets.cc
+    :language: c++
+    :linenos:
+    :caption: docs/source/code_examples/stubnets/stubnets.cc
 
-    #include "kernel/yosys.h"
-    USING_YOSYS_NAMESPACE
+.. literalinclude:: /code_examples/stubnets/Makefile
+    :language: makefile
+    :linenos:
+    :caption: docs/source/code_examples/stubnets/Makefile
 
-    struct MyPass : public Pass {
-        MyPass() : Pass("my_cmd", "just a simple test") { }
-        virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
-        {
-            log("Arguments to my_cmd:\n");
-            for (auto &arg : args)
-            log("  %s\n", arg.c_str());
-
-            log("Modules in current design:\n");
-            for (auto mod : design->modules())
-            log("  %s (%d wires, %d cells)\n", log_id(mod),
-                GetSize(mod->wires()), GetSize(mod->cells()));
-        }
-    } MyPass;
-
-Creating a plugin
-~~~~~~~~~~~~~~~~~
-
-Yosys can be extended by adding additional C++ code to the Yosys code base, or
-by loading plugins into Yosys.
-
-Use the following command to compile a Yosys plugin:
-
-.. code::
-
-    yosys-config --exec --cxx --cxxflags --ldflags \
-             -o my_cmd.so -shared my_cmd.cc --ldlibs
-
-Or shorter:
-
-.. code::
-
-    yosys-config --build my_cmd.so my_cmd.cc
-
-Load the plugin using the yosys ``-m`` option:
-
-.. code::
-
-    yosys -m ./my_cmd.so -p 'my_cmd foo bar'
+.. literalinclude:: /code_examples/stubnets/test.v
+    :language: verilog
+    :linenos:
+    :caption: docs/source/code_examples/stubnets/test.v