Add full_pmux feature to pmux2shiftx

Signed-off-by: Clifford Wolf <clifford@clifford.at>

diff --git a/passes/opt/pmux2shiftx.cc b/passes/opt/pmux2shiftx.cc
index 5f897b13120f33acbf7eed0fb8c53493b8c74bce..29870f510fa3fcfdf7102304a94fa1c46764ebe1 100644 (file)
--- a/passes/opt/pmux2shiftx.cc
+++ b/passes/opt/pmux2shiftx.cc
@@ -369,6 +369,7 @@ struct Pmux2ShiftxPass : public Pass {
 
                                dict<SigSpec, pool<int>> seldb;
 
+                               SigSpec A = cell->getPort("\\A");
                                SigSpec B = cell->getPort("\\B");
                                SigSpec S = sigmap(cell->getPort("\\S"));
                                for (int i = 0; i < GetSize(S); i++)
@@ -419,6 +420,8 @@ struct Pmux2ShiftxPass : public Pass {
                                                choices[val] = i;
                                        }
 
+                                       bool full_pmux = GetSize(choices) == GetSize(S);
+
                                        // TBD: also find choices that are using signals that are subsets of the bits in "sig"
 
                                        if (!verbose)
@@ -634,7 +637,21 @@ struct Pmux2ShiftxPass : public Pass {
                                        log("    range density: %d%%\n", range_density);
                                        log("    absolute density: %d%%\n", absolute_density);
 
-                                       bool full_case = (min_choice == 0) && (max_choice == (1 << GetSize(sig))-1) && (max_choice+1 == GetSize(choices));
+                                       if (full_pmux) {
+                                               int full_density = 100*GetSize(choices) / (1 << GetSize(sig));
+                                               log("    full density: %d%%\n", full_density);
+                                               if (full_density < min_density) {
+                                                       full_pmux = false;
+                                               } else {
+                                                       min_choice = 0;
+                                                       max_choice = (1 << GetSize(sig))-1;
+                                                       log("    update to full case.\n");
+                                                       log("    new min choice: %d\n", min_choice);
+                                                       log("    new max choice: %d\n", max_choice);
+                                               }
+                                       }
+
+                                       bool full_case = (min_choice == 0) && (max_choice == (1 << GetSize(sig))-1) && (full_pmux || max_choice+1 == GetSize(choices));
                                        log("    full case: %s\n", full_case ? "true" : "false");
 
                                        // check density percentages
@@ -677,6 +694,10 @@ struct Pmux2ShiftxPass : public Pass {
 
                                        // create data signal
                                        SigSpec data(State::Sx, (max_choice+1)*extwidth);
+                                       if (full_pmux) {
+                                               for (int i = 0; i <= max_choice; i++)
+                                                       data.replace(i*extwidth, A);
+                                       }
                                        for (auto &it : perm_choices) {
                                                int position = it.first.as_int()*extwidth;
                                                int data_index = it.second;