From ff7466df6e54a548fa58303993cad8fcf9728a1b Mon Sep 17 00:00:00 2001
From: Vern Paxson <vern@corelight.com>
Date: Tue, 23 Jul 2024 15:31:59 -0700
Subject: [PATCH] minor optimization of boolean comparisons

---
 src/script_opt/Expr.cc | 26 ++++++++++++++++++++++----
 src/script_opt/Stmt.cc |  6 ++++++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/src/script_opt/Expr.cc b/src/script_opt/Expr.cc
index 1ad24c5277..353604f1a7 100644
--- a/src/script_opt/Expr.cc
+++ b/src/script_opt/Expr.cc
@@ -1238,10 +1238,28 @@ ExprPtr EqExpr::Reduce(Reducer* c, StmtPtr& red_stmt) {
     if ( IsHasElementsTest() )
         return BuildHasElementsTest()->Reduce(c, red_stmt);
 
-    if ( GetType()->Tag() == TYPE_BOOL && same_singletons(op1, op2) ) {
-        bool t = Tag() == EXPR_EQ;
-        auto res = with_location_of(make_intrusive<ConstExpr>(val_mgr->Bool(t)), this);
-        return res->Reduce(c, red_stmt);
+    if ( GetType()->Tag() == TYPE_BOOL ) {
+        if ( same_singletons(op1, op2) ) {
+            bool t = Tag() == EXPR_EQ;
+            auto res = with_location_of(make_intrusive<ConstExpr>(val_mgr->Bool(t)), this);
+            return res->Reduce(c, red_stmt);
+        }
+
+        if ( op1->GetType()->Tag() == TYPE_BOOL ) {
+            if ( op1->Tag() == EXPR_CONST )
+                std::swap(op1, op2);
+
+            if ( op2->Tag() == EXPR_CONST ) {
+                bool t = Tag() == EXPR_EQ;
+                if ( op2->AsConstExpr()->Value()->IsZero() )
+                    t = ! t;
+                if ( t )
+                    return op1->Reduce(c, red_stmt);
+
+                auto res = with_location_of(make_intrusive<NotExpr>(op1), this);
+                return res->Reduce(c, red_stmt);
+            }
+        }
     }
 
     return BinaryExpr::Reduce(c, red_stmt);
diff --git a/src/script_opt/Stmt.cc b/src/script_opt/Stmt.cc
index 618d52ebda..8ef72c60b4 100644
--- a/src/script_opt/Stmt.cc
+++ b/src/script_opt/Stmt.cc
@@ -245,6 +245,12 @@ StmtPtr IfStmt::DoReduce(Reducer* c) {
             red_e_stmt = cond_red_stmt;
     }
 
+    // Check again for negation given above reductions/replacements.
+    if ( e->Tag() == EXPR_NOT ) {
+        std::swap(s1, s2);
+        e = e->GetOp1();
+    }
+
     StmtPtr sl;
 
     if ( e->IsConst() ) {