From 7bc5df8460803de5f4d989259b597cd477682334 Mon Sep 17 00:00:00 2001
From: Vaibhav Thakkar <vaibhav.thakkar.22.12.99@gmail.com>
Date: Thu, 21 Sep 2023 14:33:48 +0530
Subject: [PATCH] fix VisitDeclRefExpr for constructors in reverse mode

---
 lib/Differentiator/ReverseModeVisitor.cpp | 12 ++++++---
 test/Gradient/MemberFunctions.C           | 33 +++++++++++++++++++++++
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/lib/Differentiator/ReverseModeVisitor.cpp b/lib/Differentiator/ReverseModeVisitor.cpp
index 55256330e..6c5d09cc2 100644
--- a/lib/Differentiator/ReverseModeVisitor.cpp
+++ b/lib/Differentiator/ReverseModeVisitor.cpp
@@ -2440,11 +2440,17 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
     // need to call `Visit` since non-local variables are not differentiated.
     if (!isDerivativeOfRefType) {
       Expr* derivedE = BuildDeclRef(VDDerived);
-      initDiff = VD->getInit() ? Visit(VD->getInit(), derivedE) : StmtDiff{};
+      initDiff = StmtDiff{};
+      if (VD->getInit()) {
+        if (isa<CXXConstructExpr>(VD->getInit()))
+          initDiff = Visit(VD->getInit());
+        else
+          initDiff = Visit(VD->getInit(), derivedE);
+      }
 
       // If we are differentiating `VarDecl` corresponding to a local variable
       // inside a loop, then we need to reset it to 0 at each iteration.
-      // 
+      //
       // for example, if defined inside a loop,
       // ```
       // double localVar = i;
@@ -2454,7 +2460,7 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
       // {
       //   *_d_i += _d_localVar;
       //   _d_localVar = 0;
-      // }                        
+      // }
       if (isInsideLoop) {
         Stmt* assignToZero = BuildOp(BinaryOperatorKind::BO_Assign,
                                      BuildDeclRef(VDDerived),
diff --git a/test/Gradient/MemberFunctions.C b/test/Gradient/MemberFunctions.C
index a6ffeac36..03c6b07fe 100644
--- a/test/Gradient/MemberFunctions.C
+++ b/test/Gradient/MemberFunctions.C
@@ -786,6 +786,10 @@ double fn2(SimpleFunctions& sf, double i) {
 // CHECK-NEXT:     }
 // CHECK-NEXT: }
 
+double fn3(double x, double y, double i, double j) {
+  SimpleFunctions sf(x, y);
+  return sf.mem_fn(i, j);
+}
 
 int main() {
   auto d_mem_fn = clad::gradient(&SimpleFunctions::mem_fn);
@@ -880,4 +884,33 @@ int main() {
   // CHECK-NEXT:           * _d_j += _r3;
   // CHECK-NEXT:       }
   // CHECK-NEXT:   }
+
+  auto d_fn3 = clad::gradient(fn3, "i,j");
+  result[0] = result[1] = 0;
+  d_fn3.execute(2, 3, 4, 5, &result[0], &result[1]);
+  printf("%.2f %.2f", result[0], result[1]); // CHECK-EXEC: 10.00 4.00
+
+  // CHECK: void fn3_grad_2_3(double x, double y, double i, double j, clad::array_ref<double> _d_i, clad::array_ref<double> _d_j) {
+// CHECK-NEXT:     double _d_x = 0;
+// CHECK-NEXT:     double _d_y = 0;
+// CHECK-NEXT:     SimpleFunctions _d_sf({});
+// CHECK-NEXT:     double _t0;
+// CHECK-NEXT:     double _t1;
+// CHECK-NEXT:     SimpleFunctions _t2;
+// CHECK-NEXT:     SimpleFunctions sf(x, y);
+// CHECK-NEXT:     _t0 = i;
+// CHECK-NEXT:     _t1 = j;
+// CHECK-NEXT:     _t2 = sf;
+// CHECK-NEXT:     goto _label0;
+// CHECK-NEXT:   _label0:
+// CHECK-NEXT:     {
+// CHECK-NEXT:         double _grad0 = 0.;
+// CHECK-NEXT:         double _grad1 = 0.;
+// CHECK-NEXT:         _t2.mem_fn_pullback(_t0, _t1, 1, &_d_sf, &_grad0, &_grad1);
+// CHECK-NEXT:         double _r0 = _grad0;
+// CHECK-NEXT:         * _d_i += _r0;
+// CHECK-NEXT:         double _r1 = _grad1;
+// CHECK-NEXT:         * _d_j += _r1;
+// CHECK-NEXT:     }
+// CHECK-NEXT: }
 }