diff options
Diffstat (limited to 'CodingReadme')
| -rw-r--r-- | CodingReadme | 50 |
1 files changed, 49 insertions, 1 deletions
diff --git a/CodingReadme b/CodingReadme index 5800e30c3..7d4ded93d 100644 --- a/CodingReadme +++ b/CodingReadme @@ -21,7 +21,7 @@ Here is a the C++ code for a "hello_world" Yosys command (hello.cc): struct HelloWorldPass : public Pass { HelloWorldPass() : Pass("hello_world") { } - virtual void execute(vector<string>, Design*) { + void execute(vector<string>, Design*) override { log("Hello World!\n"); } } HelloWorldPass; @@ -202,6 +202,52 @@ of how to use the Yosys API: manual/PRESENTATION_Prog/my_cmd.cc +Script Passes +------------- + +The ScriptPass base class can be used to implement passes that just call other passes, +like a script. Examples for such passes are: + + techlibs/common/prep.cc + techlibs/common/synth.cc + +In some cases it is easier to implement such a pass as regular pass, for example when +ScriptPass doesn't provide the type of flow control desired. (But many of the +script passes in Yosys that don't use ScriptPass simply predate the ScriptPass base +class.) Examples for such passes are: + + passes/opt/opt.cc + passes/proc/proc.cc + +Whether they use the ScriptPass base-class or not, a pass should always either +call other passes without doing any non-trivial work itself, or should implement +a non-trivial algorithm but not call any other passes. The reason for this is that +this helps containing complexity in individual passes and simplifies debugging the +entire system. + +Exceptions to this rule should be rare and limited to cases where calling other +passes is optional and only happens when requested by the user (such as for +example `techmap -autoproc`), or where it is about commands that are "top-level +commands" in their own right, not components to be used in regular synthesis +flows (such as the `bugpoint` command). + +A pass that would "naturally" call other passes and also do some work itself +should be re-written in one of two ways: + +1) It could be re-written as script pass with the parts that are not calls +to other passes factored out into individual new passes. Usually in those +cases the new sub passes share the same prefix as the top-level script pass. + +2) It could be re-written so that it already expects the design in a certain +state, expecting the calling script to set up this state before calling the +pass in questions. + +Many back-ends are examples for the 2nd approach. For example, `write_aiger` +does not convert the design into AIG representation, but expects the design +to be already in this form, and prints an `Unsupported cell type` error +message otherwise. + + Notes on the existing codebase ------------------------------ @@ -373,6 +419,7 @@ Finally run all tests with "make config-{clang,gcc,gcc-4.8}": cd ~yosys make clean make test + make ystests make vloghtb make install @@ -389,6 +436,7 @@ Finally run all tests with "make config-{clang,gcc,gcc-4.8}": Release: - set YOSYS_VER to x.y.z in Makefile + - remove "bumpversion" target from Makefile - update version string in CHANGELOG git commit -am "Yosys x.y.z" |