From ed250cc147363f958bfd9d0dbb5b3d4ee959763d Mon Sep 17 00:00:00 2001
From: Brian Taylor <lbwnet@comcast.net>
Date: Thu, 28 Mar 2024 15:11:38 -0700
Subject: [PATCH] Fix bug in the LOGICEXP scan_gates optimizer. Some gates with
 an inverting output were generated with bad logic which gave incorrect
 simulation results.

---
 src/frontend/logicexp.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/src/frontend/logicexp.c b/src/frontend/logicexp.c
index 8e1c5a688..60b715fa6 100644
--- a/src/frontend/logicexp.c
+++ b/src/frontend/logicexp.c
@@ -22,6 +22,7 @@
 #include "ngspice/dstring.h"
 #include "ngspice/logicexp.h"
 #include "ngspice/udevices.h"
+#include "ngspice/cpextern.h"
 
 static char *get_pindly_instance_name(void);
 static char *get_inst_name(void);
@@ -573,6 +574,21 @@ static void scan_gates(DSTRING *lhs)
 {
     struct gate_data *current = NULL, *previous = NULL, *last_curr = NULL;
     struct gate_data *prev = NULL;
+    int ps_scan_gates_noopt = 0;
+
+    if (!cp_getvar("ps_scan_gates_noopt", CP_NUM, &ps_scan_gates_noopt, 0)) {
+        ps_scan_gates_noopt = 0;
+    }
+    if (ps_scan_gates_noopt) {
+        current = last_gate;
+        if (ds_get_length(lhs) > 0) {
+            assert(current->finished == FALSE);
+            tfree(current->outp);
+            current->outp = TMALLOC(char, ds_get_length(lhs) + 1);
+            strcpy(current->outp, ds_get_buf(lhs));
+        }
+        return;
+    }
 
     current = first_gate;
     while (current) {
@@ -638,19 +654,6 @@ static void scan_gates(DSTRING *lhs)
     }
 }
 
-static void scan_gates_noopt(DSTRING *lhs)
-{
-    struct gate_data *current = NULL;
-
-    current = last_gate;
-    if (ds_get_length(lhs) > 0) {
-        assert(current->finished == FALSE);
-        tfree(current->outp);
-        current->outp = TMALLOC(char, ds_get_length(lhs) + 1);
-        strcpy(current->outp, ds_get_buf(lhs));
-    }
-}
-
 static void gen_scanned_gates(struct gate_data *gp)
 {
     DS_CREATE(instance, 64);
@@ -1141,11 +1144,7 @@ static BOOL bstmt_postfix(void)
         retval = FALSE;
         goto bail_out;
     }
-if (getenv("SCAN_NOOPT")) {
-    scan_gates_noopt(&lhs);
-} else {
     scan_gates(&lhs);
-}
     gen_scanned_gates(first_gate);
     lookahead = lex_scan();
     while (lookahead != '}') {