From 1d56ef8997a3225d7d37cde4383de2caf54e8574 Mon Sep 17 00:00:00 2001
From: Vaibhav Thakkar <vaibhav.thakkar.22.12.99@gmail.com>
Date: Sat, 29 Jun 2024 18:16:16 +0200
Subject: [PATCH] Add support for const cast in fwd mode

---
 .../Differentiator/BaseForwardModeVisitor.h   |  1 +
 lib/Differentiator/BaseForwardModeVisitor.cpp | 19 +++++++++++++
 test/ForwardMode/Pointer.C                    | 28 +++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/include/clad/Differentiator/BaseForwardModeVisitor.h b/include/clad/Differentiator/BaseForwardModeVisitor.h
index 484d17d4b..311fc5769 100644
--- a/include/clad/Differentiator/BaseForwardModeVisitor.h
+++ b/include/clad/Differentiator/BaseForwardModeVisitor.h
@@ -55,6 +55,7 @@ class BaseForwardModeVisitor
   StmtDiff VisitCallExpr(const clang::CallExpr* CE);
   StmtDiff VisitCompoundStmt(const clang::CompoundStmt* CS);
   StmtDiff VisitConditionalOperator(const clang::ConditionalOperator* CO);
+  StmtDiff VisitCXXConstCastExpr(const clang::CXXConstCastExpr* CCE);
   StmtDiff VisitCXXBoolLiteralExpr(const clang::CXXBoolLiteralExpr* BL);
   StmtDiff VisitCharacterLiteral(const clang::CharacterLiteral* CL);
   StmtDiff VisitStringLiteral(const clang::StringLiteral* SL);
diff --git a/lib/Differentiator/BaseForwardModeVisitor.cpp b/lib/Differentiator/BaseForwardModeVisitor.cpp
index 067fd77d1..2e26444e4 100644
--- a/lib/Differentiator/BaseForwardModeVisitor.cpp
+++ b/lib/Differentiator/BaseForwardModeVisitor.cpp
@@ -1600,6 +1600,25 @@ StmtDiff BaseForwardModeVisitor::VisitImplicitValueInitExpr(
   return StmtDiff(Clone(E), Clone(E));
 }
 
+StmtDiff
+BaseForwardModeVisitor::VisitCXXConstCastExpr(const CXXConstCastExpr* CCE) {
+  StmtDiff subExprDiff = Visit(CCE->getSubExpr());
+  Expr* castExpr =
+      m_Sema
+          .BuildCXXNamedCast(CCE->getBeginLoc(), tok::kw_const_cast,
+                             CCE->getTypeInfoAsWritten(), subExprDiff.getExpr(),
+                             CCE->getAngleBrackets(), CCE->getSourceRange())
+          .get();
+  Expr* castExprDiff =
+      m_Sema
+          .BuildCXXNamedCast(CCE->getBeginLoc(), tok::kw_const_cast,
+                             CCE->getTypeInfoAsWritten(),
+                             subExprDiff.getExpr_dx(), CCE->getAngleBrackets(),
+                             CCE->getSourceRange())
+          .get();
+  return StmtDiff(castExpr, castExprDiff);
+}
+
 StmtDiff
 BaseForwardModeVisitor::VisitCStyleCastExpr(const CStyleCastExpr* CSCE) {
   StmtDiff subExprDiff = Visit(CSCE->getSubExpr());
diff --git a/test/ForwardMode/Pointer.C b/test/ForwardMode/Pointer.C
index cfe3598a1..317cd28a5 100644
--- a/test/ForwardMode/Pointer.C
+++ b/test/ForwardMode/Pointer.C
@@ -174,6 +174,29 @@ double fn7(double i) {
 // CHECK-NEXT:     return _d_res;
 // CHECK-NEXT: }
 
+void* cling_runtime_internal_throwIfInvalidPointer(void *Sema, void *Expr, const void *Arg) {
+  return const_cast<void*>(Arg);
+}
+
+double fn8(double* params) {
+  double arr[] = {3.0};
+  return params[0]*params[0] + *(double*)(cling_runtime_internal_throwIfInvalidPointer((void*)0UL, (void*)0UL, arr));
+}
+
+// CHECK: clad::ValueAndPushforward<void *, void *> cling_runtime_internal_throwIfInvalidPointer_pushforward(void *Sema, void *Expr, const void *Arg, void *_d_Sema, void *_d_Expr, const void *_d_Arg);
+
+// CHECK: double fn8_darg0_0(double *params) {
+// CHECK-NEXT:     double _d_arr[1] = {0.};
+// CHECK-NEXT:     double arr[1] = {3.};
+// CHECK-NEXT:     clad::ValueAndPushforward<void *, void *> _t0 = cling_runtime_internal_throwIfInvalidPointer_pushforward((void *)0UL, (void *)0UL, arr, (void *)0UL, (void *)0UL, _d_arr);
+// CHECK-NEXT:     return 1. * params[0] + params[0] * 1. + *(double *)_t0.pushforward;
+// CHECK-NEXT: }
+
+// CHECK: clad::ValueAndPushforward<void *, void *> cling_runtime_internal_throwIfInvalidPointer_pushforward(void *Sema, void *Expr, const void *Arg, void *_d_Sema, void *_d_Expr, const void *_d_Arg) {
+// CHECK-NEXT:     return {const_cast<void *>(Arg), const_cast<void *>(_d_Arg)};
+// CHECK-NEXT: }
+
+
 int main() {
   INIT_DIFFERENTIATE(fn1, "i");
   INIT_DIFFERENTIATE(fn2, "i");
@@ -190,4 +213,9 @@ int main() {
   TEST_DIFFERENTIATE(fn5, 3, 5);  // CHECK-EXEC: {57.00}
   TEST_DIFFERENTIATE(fn6, 3);     // CHECK-EXEC: {1.00}
   TEST_DIFFERENTIATE(fn7, 3);     // CHECK-EXEC: {4.00}
+
+  double params[] = {3.0};
+  auto fn8_dx = clad::differentiate(fn8, "params[0]");
+  double d_param = fn8_dx.execute(params);
+  printf("{%.2f}\n", d_param); // CHECK-EXEC: {6.00}
 }