proc_clean: Fix empty case removal conditions.

Fixes #2639.

diff --git a/passes/proc/proc_clean.cc b/passes/proc/proc_clean.cc
index 5e78b7316dced96d93bc59e5b10a8bb211477d25..54d5a81ff22a75584f16641e7a27bdc04ae09f4b 100644 (file)
--- a/passes/proc/proc_clean.cc
+++ b/passes/proc/proc_clean.cc
@@ -76,22 +76,33 @@ void proc_clean_switch(RTLIL::SwitchRule *sw, RTLIL::CaseRule *parent, bool &did
        }
        else
        {
-               bool all_fully_def = true;
                for (auto cs : sw->cases)
-               {
                        if (max_depth != 0)
                                proc_clean_case(cs, did_something, count, max_depth-1);
-                       int size = 0;
-                       for (auto cmp : cs->compare)
+
+               bool is_parallel_case = sw->get_bool_attribute(ID::parallel_case);
+               bool is_full_case = sw->get_bool_attribute(ID::full_case);
+
+               // Empty case removal.  The rules are:
+               //
+               // - for full_case: only remove cases if *all* cases are empty
+               // - for parallel_case but not full_case: remove any empty case
+               // - for non-parallel and non-full case: remove the final case if it's empty
+
+               if (is_full_case)
+               {
+                       bool all_empty = true;
+                       for (auto cs : sw->cases)
+                               if (!cs->empty())
+                                       all_empty = false;
+                       if (all_empty)
                        {
-                               size += cmp.size();
-                               if (!cmp.is_fully_def())
-                                       all_fully_def = false;
+                               for (auto cs : sw->cases)
+                                       delete cs;
+                               sw->cases.clear();
                        }
-                       if (sw->signal.size() != size)
-                               all_fully_def = false;
                }
-               if (all_fully_def)
+               else if (is_parallel_case)
                {
                        for (auto cs = sw->cases.begin(); cs != sw->cases.end();)
                        {