From a6015863d8a48e7a69a26e5930caf151301b0d4c Mon Sep 17 00:00:00 2001
From: Ryszard Rozak <rrozak@antmicro.com>
Date: Fri, 21 Jul 2023 09:27:00 +0200
Subject: [PATCH] Support for static method calls as default values of function
 arguments (#4378)

---
 src/V3Task.cpp                   | 21 ++++++++++++++++-----
 test_regress/t/t_func_defaults.v | 16 ++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/V3Task.cpp b/src/V3Task.cpp
index 5fbd76ce3..163b5d37e 100644
--- a/src/V3Task.cpp
+++ b/src/V3Task.cpp
@@ -1546,6 +1546,13 @@ private:
         iterateChildren(nodep);
         m_insStmtp = nullptr;  // Next thing should be new statement
     }
+    void visit(AstVar* nodep) override {
+        if (nodep->isFuncLocal() && nodep->direction() == VDirection::INPUT && nodep->valuep()) {
+            // It's the default value of optional argument.
+            // Such values are added to function calls on this stage and aren't needed here.
+            pushDeletep(nodep->valuep()->unlinkFrBack());
+        }
+    }
     void visit(AstStmtExpr* nodep) override {
         m_insMode = IM_BEFORE;
         m_insStmtp = nodep;
@@ -1658,7 +1665,14 @@ V3TaskConnects V3Task::taskConnects(AstNodeFTaskRef* nodep, AstNode* taskStmtsp)
                                << portp->prettyNameQ() << " in function call to "
                                << nodep->taskp()->prettyTypeName());
                 newvaluep = new AstConst{nodep->fileline(), AstConst::Unsized32{}, 0};
-            } else if (!VN_IS(portp->valuep(), Const)) {
+            } else if (AstFuncRef* const funcRefp = VN_CAST(portp->valuep(), FuncRef)) {
+                const AstNodeFTask* const funcp = funcRefp->taskp();
+                if (funcp->classMethod() && funcp->lifetime().isStatic()) newvaluep = funcRefp;
+            } else if (AstConst* const constp = VN_CAST(portp->valuep(), Const)) {
+                newvaluep = constp;
+            }
+
+            if (!newvaluep) {
                 // The default value for this port might be a constant
                 // expression that hasn't been folded yet. Try folding it
                 // now; we don't have much to lose if it fails.
@@ -1672,12 +1686,9 @@ V3TaskConnects V3Task::taskConnects(AstNodeFTaskRef* nodep, AstNode* taskStmtsp)
                                       << portp->prettyNameQ() << " in function call to "
                                       << nodep->taskp()->prettyTypeName());
                     newvaluep = new AstConst{nodep->fileline(), AstConst::Unsized32{}, 0};
-                } else {
-                    newvaluep = newvaluep->cloneTree(true);
                 }
-            } else {
-                newvaluep = VN_AS(portp->valuep(), NodeExpr)->cloneTree(true);
             }
+            newvaluep = newvaluep->cloneTree(true);
             // To avoid problems with callee needing to know to deleteTree
             // or not, we make this into a pin
             UINFO(9, "Default pin for " << portp << endl);
diff --git a/test_regress/t/t_func_defaults.v b/test_regress/t/t_func_defaults.v
index 7928a0bce..3d360fa7a 100644
--- a/test_regress/t/t_func_defaults.v
+++ b/test_regress/t/t_func_defaults.v
@@ -19,6 +19,17 @@ function automatic logic [1:0] foo
    return x + y;
 endfunction
 
+class Foo;
+   static int x;
+   function static int get_x;
+      return x;
+   endfunction
+endclass
+
+function int mult2(int x = Foo::get_x());
+   return 2 * x;
+endfunction
+
 module t (/*AUTOARG*/);
    logic [1:0] foo_val;
 
@@ -26,6 +37,11 @@ module t (/*AUTOARG*/);
       foo_val = foo();
       if (foo_val != 2'b10) $stop;
 
+      if (mult2(1) != 2) $stop;
+      if (mult2() != 0) $stop;
+      Foo::x = 30;
+      if (mult2() != 60) $stop;
+
       $write("*-* All Finished *-*\n");
       $finish;
    end