Rework muxcover decoder gen if more significant muxes are 1'bx

diff --git a/passes/techmap/muxcover.cc b/passes/techmap/muxcover.cc
index b0722134e3bc867826757e56ad8cc7dec181f57b..0f86aeff0d246211a0f9b0b821f797513f6d3e88 100644 (file)
--- a/passes/techmap/muxcover.cc
+++ b/passes/techmap/muxcover.cc
@@ -324,13 +324,7 @@ struct MuxcoverWorker
                        ok = ok && follow_muxtree(G, tree, bit, "BBA");
                        ok = ok && follow_muxtree(H, tree, bit, "BBB");
 
-                       ok = ok && follow_muxtree(S1, tree, bit, "AAS");
-                       ok = ok && follow_muxtree(S2, tree, bit, "ABS");
-                       ok = ok && follow_muxtree(S3, tree, bit, "BAS");
-                       ok = ok && follow_muxtree(S4, tree, bit, "BBS");
-
-                       if (nodecode)
-                               ok = ok && S1 == S2 && S2 == S3 && S3 == S4;
+                       ok = ok && follow_muxtree(U1, tree, bit, "S");
 
                        ok = ok && follow_muxtree(T1, tree, bit, "AS");
                        ok = ok && follow_muxtree(T2, tree, bit, "BS");
@@ -338,7 +332,14 @@ struct MuxcoverWorker
                        if (nodecode)
                                ok = ok && T1 == T2;
 
-                       ok = ok && follow_muxtree(U1, tree, bit, "S");
+                       ok = ok && follow_muxtree(S1, tree, bit, "AAS");
+                       ok = ok && follow_muxtree(S2, tree, bit, "ABS");
+                       ok = ok && follow_muxtree(S3, tree, bit, "BAS");
+                       ok = ok && follow_muxtree(S4, tree, bit, "BBS");
+
+                       if (nodecode)
+                               ok = ok && S1 == S2 && /*S2 == S3 &&*/ S3 == S4;
+                                                      // ^^ Should already be checked by T1 == T2 above
 
                        if (ok)
                        {
@@ -353,12 +354,16 @@ struct MuxcoverWorker
                                mux.inputs.push_back(G);
                                mux.inputs.push_back(H);
 
-                               mux.cost += prepare_decode_mux(S1, S2, T1, bit);
-                               mux.cost += prepare_decode_mux(S3, S4, T2, bit);
-                               mux.cost += prepare_decode_mux(S1, S3, U1, bit);
-
                                mux.cost += prepare_decode_mux(T1, T2, U1, bit);
 
+                               if (T1 != RTLIL::Sx) {
+                                       mux.cost += prepare_decode_mux(S1, S2, T1, bit);
+                                       mux.cost += prepare_decode_mux(S3, S4, T2, bit);
+                                       mux.cost += prepare_decode_mux(S1, S3, U1, bit);
+                               }
+                               else
+                                       S1 = RTLIL::Sx;
+
                                mux.selects.push_back(S1);
                                mux.selects.push_back(T1);
                                mux.selects.push_back(U1);
@@ -397,17 +402,13 @@ struct MuxcoverWorker
                        ok = ok && follow_muxtree(O, tree, bit, "BBBA");
                        ok = ok && follow_muxtree(P, tree, bit, "BBBB");
 
-                       ok = ok && follow_muxtree(S1, tree, bit, "AAAS");
-                       ok = ok && follow_muxtree(S2, tree, bit, "AABS");
-                       ok = ok && follow_muxtree(S3, tree, bit, "ABAS");
-                       ok = ok && follow_muxtree(S4, tree, bit, "ABBS");
-                       ok = ok && follow_muxtree(S5, tree, bit, "BAAS");
-                       ok = ok && follow_muxtree(S6, tree, bit, "BABS");
-                       ok = ok && follow_muxtree(S7, tree, bit, "BBAS");
-                       ok = ok && follow_muxtree(S8, tree, bit, "BBBS");
+                       ok = ok && follow_muxtree(V1, tree, bit, "S");
+
+                       ok = ok && follow_muxtree(U1, tree, bit, "AS");
+                       ok = ok && follow_muxtree(U2, tree, bit, "BS");
 
                        if (nodecode)
-                               ok = ok && S1 == S2 && S2 == S3 && S3 == S4 && S4 == S5 && S5 == S6 && S6 == S7 && S7 == S8;
+                               ok = ok && U1 == U2;
 
                        ok = ok && follow_muxtree(T1, tree, bit, "AAS");
                        ok = ok && follow_muxtree(T2, tree, bit, "ABS");
@@ -415,15 +416,20 @@ struct MuxcoverWorker
                        ok = ok && follow_muxtree(T4, tree, bit, "BBS");
 
                        if (nodecode)
-                               ok = ok && T1 == T2 && T2 == T3 && T3 == T4;
+                               ok = ok && T1 == T2 && /*T2 == T3 &&*/ T3 == T4;
+                                                      // ^^ Should already be checked by U1 == U2 above
 
-                       ok = ok && follow_muxtree(U1, tree, bit, "AS");
-                       ok = ok && follow_muxtree(U2, tree, bit, "BS");
+                       ok = ok && follow_muxtree(S1, tree, bit, "AAAS");
+                       ok = ok && follow_muxtree(S2, tree, bit, "AABS");
+                       ok = ok && follow_muxtree(S3, tree, bit, "ABAS");
+                       ok = ok && follow_muxtree(S4, tree, bit, "ABBS");
+                       ok = ok && follow_muxtree(S5, tree, bit, "BAAS");
+                       ok = ok && follow_muxtree(S6, tree, bit, "BABS");
+                       ok = ok && follow_muxtree(S7, tree, bit, "BBAS");
+                       ok = ok && follow_muxtree(S8, tree, bit, "BBBS");
 
                        if (nodecode)
-                               ok = ok && U1 == U2;
-
-                       ok = ok && follow_muxtree(V1, tree, bit, "S");
+                               ok = ok && S1 == S2 && /*S2 == S3 &&*/ S3 == S4 && /*S4 == S5 &&*/ S5 == S6 && /*S6 == S7 &&*/ S7 == S8;
 
                        if (ok)
                        {
@@ -446,20 +452,30 @@ struct MuxcoverWorker
                                mux.inputs.push_back(O);
                                mux.inputs.push_back(P);
 
-                               mux.cost += prepare_decode_mux(S1, S2, T1, bit);
-                               mux.cost += prepare_decode_mux(S3, S4, T2, bit);
-                               mux.cost += prepare_decode_mux(S5, S6, T3, bit);
-                               mux.cost += prepare_decode_mux(S7, S8, T4, bit);
-                               mux.cost += prepare_decode_mux(S1, S3, U1, bit);
-                               mux.cost += prepare_decode_mux(S5, S7, U2, bit);
-                               mux.cost += prepare_decode_mux(S1, S5, V1, bit);
-
-                               mux.cost += prepare_decode_mux(T1, T2, U1, bit);
-                               mux.cost += prepare_decode_mux(T3, T4, U2, bit);
-                               mux.cost += prepare_decode_mux(T1, T3, V1, bit);
-
                                mux.cost += prepare_decode_mux(U1, U2, V1, bit);
 
+                               if (U1 != RTLIL::Sx) {
+                                       mux.cost += prepare_decode_mux(T1, T2, U1, bit);
+                                       mux.cost += prepare_decode_mux(T3, T4, U2, bit);
+                                       mux.cost += prepare_decode_mux(T1, T3, V1, bit);
+
+                                       if (T1 != RTLIL::Sx) {
+                                               mux.cost += prepare_decode_mux(S1, S2, T1, bit);
+                                               mux.cost += prepare_decode_mux(S3, S4, T2, bit);
+                                               mux.cost += prepare_decode_mux(S5, S6, T3, bit);
+                                               mux.cost += prepare_decode_mux(S7, S8, T4, bit);
+                                               mux.cost += prepare_decode_mux(S1, S3, U1, bit);
+                                               mux.cost += prepare_decode_mux(S5, S7, U2, bit);
+                                               mux.cost += prepare_decode_mux(S1, S5, V1, bit);
+                                       }
+                                       else
+                                               S1 = RTLIL::Sx;
+                               }
+                               else {
+                                       T1 = RTLIL::Sx;
+                                       S1 = RTLIL::Sx;
+                               }
+
                                mux.selects.push_back(S1);
                                mux.selects.push_back(T1);
                                mux.selects.push_back(U1);