Changes between Version 3 and Version 4 of Soclib Cc/Design Guide

Timestamp:

Mar 25, 2010, 12:51:24 PM (14 years ago)

Author:

Nicolas Pouillon

Comment:

--

Soclib Cc/Design Guide

@@ -9 +9 @@
    each of them is a different implementation of the same LRM, and
    yields incompatible objects
- * Templated classes, with separate implementation.
-   In order to reduce compilation time when a file changes, splitting
-   implementation from header is the right thing to do. Unfortunatelly
-   it involves manually instaciating source code for each used
-   template.
+
+ * Templated classes. The usual way of using templated code is to
+   put all code in .h, having template code emitted at use in main C++
+   file.
+
+   This is good for small utilities, but SystemC modules may
+   be more than 1000 lines-long, and more that 40 of them may be used
+   in a topcell. This may yield a single translation unit with more than
+   50000 lines of code, heavily templated. This implies some usage issues
+   (compiler getting out of memory, unreasonnable compile times)
+
+   Therefore we need two features:
+   * Separate implementation: Put template class definition and implementation
+     in two separate files. Compile them separately.
+
+     This implies template code must be explicitely instanciated with some
+     `template class Foo<parameters>;` code. It has to be done automatically.
+   * Object reuse: Once modules built separately, we can put objects
+     in a global repository and use the in a cached way.
+
  * Different build modes (debugging, profiling release, others ??)
- * Compiled objects reuse: as we may build lots of SoCs with minor
-   modifications, reusing compiled objects from one build to the other
-   seems interesting (considering templated C++ build time)
 
 === Reuse of current tools ?? ===
@@ -25 +37 @@
 readibility. 
 
+There is no build tool known out the which does object caching and
+template instantiation at the same time. Even if current build tools
+may be enhanced to do the job, this is not an easy task.
+
 This very tool has been implemented as a `make` wrapper before,
 generated Makefiles were unreadable (all templates parameters in the
-middle, ...), and it did not work so well. It had been developped in a
-week, debugged in two weeks.
+middle, ...), and it did not work so well.
 
-Soclib-cc has been totally developped in 16 hours.
 
 = Configuration =
@@ -36 +50 @@
 In order to compile SoCLib objects, we need:
  * a working SystemC installation
- * a working GNU-Bfd installation (used for loading binaries into the platform)
  * a working GNU-C++ compiler