Add docs for breakpoints (#459)

* Add docs for breakpoints
* Sort features sections

Author: vlad-perevezentsev

docs/user_guides/debugging/breakpoints.rst

@@ -0,0 +1,93 @@
+Breakpoints
+===========
+
+A `breakpoint` makes your program stop whenever a certain point in the program is reached.
+
+You can set breakpoints with the ``break`` command to specify the place where your program should stop in the kernel by line number or function name.
+
+You have several ways to set breakpoints:
+  - break function
+  - break filename:function
+  - break filename:linenumber
+  
+See also:
+  - `GDB documentation of breakpoints`_.
+
+.. _GDB documentation of breakpoints: https://sourceware.org/gdb/current/onlinedocs/gdb/Set-Breaks.html#Set-Breaks
+
+Consider ``numba-dppy`` kernel code. See source file ``numba_dppy/examples/debug/simple_sum.py``:
+
+.. literalinclude:: ../../../numba_dppy/examples/debug/simple_sum.py
+    :lines: 15-
+    :linenos:
+
+Run debugger:
+
+.. code-block:: bash
+
+    export NUMBA_DPPY_DEBUGINFO=1
+    gdb-oneapi -q --args python simple_sum.py
+
+``break function``
+------------------
+
+GDB output:
+
+.. code-block:: bash
+
+  (gdb) break data_parallel_sum
+  Breakpoint 1 (data_parallel_sum) pending.
+  (gdb) run
+
+  Thread 2.2 hit Breakpoint 1, with SIMD lanes [0-7], __main__::data_parallel_sum () at simple_sum.py:20
+  20      @dppy.kernel
+
+``break filename: linenumber``
+------------------------------
+
+GDB output:
+
+.. code-block:: bash
+
+  (gdb) break simple_sum.py:20
+  Breakpoint 1 (simple_sum.py:20) pending.
+  (gdb) run
+  
+  Thread 2.2 hit Breakpoint 1, with SIMD lanes [0-7], __main__::data_parallel_sum () at simple_sum.py:20
+  20      @dppy.kernel
+
+``break filename: function``
+----------------------------
+
+GDB output:
+
+.. code-block:: bash
+
+  (gdb) break simple_sum.py:data_parallel_sum
+  Breakpoint 1 (simple_sum.py:data_parallel_sum) pending.
+  (gdb) run
+  
+  Thread 2.2 hit Breakpoint 1, with SIMD lanes [0-7], __main__::data_parallel_sum () at simple_sum.py:20
+  20      @dppy.kernel
+
+Breakpoints with nested functions
+-------------------------------------
+
+Consider ``numba-dppy`` kernel code. See source file ``numba_dppy/examples/debug/simple_dppy_func.py``:
+
+.. literalinclude:: ../../../numba_dppy/examples/debug/simple_dppy_func.py
+    :lines: 15-
+    :linenos:
+
+GDB output:
+
+.. code-block:: bash
+
+  export NUMBA_DPPY_DEBUGINFO=1
+  gdb-oneapi -q --args python simple_sum.py
+  (gdb) break func_sum
+  Breakpoint 1 (func_sum) pending.
+  (gdb) run
+
+  Thread 2.2 hit Breakpoint 1, with SIMD lanes [0-7], __main__::func_sum () at simple_dppy_func.py:22
+  22      result = a_in_func + b_in_func

docs/user_guides/debugging/features.rst

@@ -21,7 +21,8 @@ Currently, the following debugging features are available:
 .. toctree::
     :maxdepth: 2
 
-    local_variables
+    breakpoints
     stepping
-    info
+    local_variables
     backtrace
+    info