Optimize returns at end of functions.

src/V3Ast.cpp

@@ -94,6 +94,15 @@ void AstNode::init() {
     m_user5Cnt = 0;
 }
 
+AstNode* AstNode::abovep() const {
+    // m_headtailp only valid at beginning or end of list
+    // Avoid supporting at other locations as would require walking
+    // list which is likely to cause performance issues.
+    UASSERT_OBJ(!m_nextp || firstAbovep(), this, "abovep() not allowed when in midlist");
+    const AstNode* firstp = firstAbovep() ? this : m_headtailp;
+    return firstp->backp();
+}
+
 string AstNode::encodeName(const string& namein) {
     // Encode signal name raw from parser, then not called again on same signal
     string out;

src/V3Ast.h

@@ -1243,6 +1243,7 @@ public:
     const char* typeName() const { return type().ascii(); }  // See also prettyTypeName
     AstNode* nextp() const { return m_nextp; }
     AstNode* backp() const { return m_backp; }
+    AstNode* abovep() const;  // Parent node above, only when no nextp() as otherwise slow
     AstNode* op1p() const { return m_op1p; }
     AstNode* op2p() const { return m_op2p; }
     AstNode* op3p() const { return m_op3p; }

src/V3Const.cpp

@@ -2180,7 +2180,20 @@ private:
     virtual void visit(AstJumpGo* nodep) {
         iterateChildren(nodep);
         m_hasJumpGo = true;
-        if (m_doExpensive) { nodep->labelp()->user4(true); }
+        if (m_doExpensive) {
+            // If last statement in a jump label we have JumpLabel(...., JumpGo)
+            // Often caused by "return" in a Verilog function.  The Go is pointless, remove.
+            if (!nodep->nextp()) {
+                if (AstJumpLabel* aboveLabelp = VN_CAST(nodep->abovep(), JumpLabel)) {
+                    if (aboveLabelp == nodep->labelp()) {
+                        UINFO(4, "JUMPGO => last remove "<<nodep<<endl);
+                        nodep->unlinkFrBack()->deleteTree(); VL_DANGLING(nodep);
+                        return;
+                    }
+                }
+            }
+            nodep->labelp()->user4(true);
+        }
     }
 
     virtual void visit(AstJumpLabel* nodep) {