Fix pointer arithmetic in fwd mode

fixes vgvassilev#978
MihailMihov · Jul 16, 2024 · 0792ff2 · 0792ff2
1 parent ef668c7
commit 0792ff2
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Showing 3 changed files with 30 additions and 8 deletions.
diff --git a/lib/Differentiator/BaseForwardModeVisitor.cpp b/lib/Differentiator/BaseForwardModeVisitor.cpp
@@ -1460,13 +1460,13 @@ BaseForwardModeVisitor::VisitBinaryOperator(const BinaryOperator* BinOp) {
     // including it as a Stmt_dx. Moreover, the fact that Stmt_dx is left
     // nullptr is used for treating expressions like ((A && B) && C) correctly.
     return StmtDiff(opDiff, nullptr);
-  }
-  if (!opDiff) {
+  } else {
     // FIXME: add support for other binary operators
     unsupportedOpWarn(BinOp->getEndLoc());
     opDiff = ConstantFolder::synthesizeLiteral(m_Context.IntTy, m_Context, 0);
   }
-  opDiff = folder.fold(opDiff);
+  if (opDiff)
+    opDiff = folder.fold(opDiff);
   // Recover the original operation from the Ldiff and Rdiff instead of
   // cloning the tree.
   Expr* op;
@@ -1499,11 +1499,19 @@ BaseForwardModeVisitor::DifferentiateVarDecl(const VarDecl* VD,
   // This may not necessarily be true in the future.
   VarDecl* VDClone =
       BuildVarDecl(VD->getType(), VD->getNameAsString(), initDiff.getExpr(),
-                   VD->isDirectInit(), nullptr, VD->getInitStyle());
+                   VD->isDirectInit(), /*TSI=*/nullptr, VD->getInitStyle());
   // FIXME: Create unique identifier for derivative.
-  VarDecl* VDDerived = BuildVarDecl(
-      VD->getType(), "_d_" + VD->getNameAsString(), initDiff.getExpr_dx(),
-      VD->isDirectInit(), nullptr, VD->getInitStyle());
+  Expr* initDx = initDiff.getExpr_dx();
+  if (VD->getType()->isPointerType() && !initDx) {
+    // initialize with nullptr.
+    // NOLINTBEGIN(cppcoreguidelines-owned-memory)
+    initDx =
+        new (m_Context) CXXNullPtrLiteralExpr(VD->getType(), VD->getBeginLoc());
+    // NOLINTEND(cppcoreguidelines-owned-memory)
+  }
+  VarDecl* VDDerived =
+      BuildVarDecl(VD->getType(), "_d_" + VD->getNameAsString(), initDx,
+                   VD->isDirectInit(), /*TSI=*/nullptr, VD->getInitStyle());
   m_Variables.emplace(VDClone, BuildDeclRef(VDDerived));
   return DeclDiff<VarDecl>(VDClone, VDDerived);
 }

diff --git a/test/ForwardMode/MemberFunctions.C b/test/ForwardMode/MemberFunctions.C
@@ -719,7 +719,7 @@ public:
   // CHECK-NEXT:       double _d_j = 0;
   // CHECK-NEXT:       SimpleFunctions _d_this_obj;
   // CHECK-NEXT:       SimpleFunctions *_d_this = &_d_this_obj;
-  // CHECK-NEXT:       double *_d_p;
+  // CHECK-NEXT:       double *_d_p = nullptr;
   // CHECK-NEXT:       double *p;
   // CHECK-NEXT:       _d_p = _d_this->arr[1];
   // CHECK-NEXT:       p = this->arr[1];

diff --git a/test/ForwardMode/Pointer.C b/test/ForwardMode/Pointer.C
@@ -203,6 +203,16 @@ double fn9(double* params, const double *constants) {
 // CHECK-NEXT:     return 1. * c0 + params[0] * _d_c0;
 // CHECK-NEXT: }
 
+double fn10(double *params, const double *constants) {
+  double c0 = *(constants + 0);
+  return params[0] * c0;
+}
+
+// CHECK: double fn10_darg0_0(double *params, const double *constants) {
+// CHECK-NEXT:     double _d_c0 = 0;
+// CHECK-NEXT:     double c0 = *(constants + 0);
+// CHECK-NEXT:     return 1. * c0 + params[0] * _d_c0;
+// CHECK-NEXT: }
 
 int main() {
   INIT_DIFFERENTIATE(fn1, "i");
@@ -230,6 +240,10 @@ int main() {
   auto fn9_dx = clad::differentiate(fn9, "params[0]");
   d_param = fn9_dx.execute(params, constants);
   printf("{%.2f}\n", d_param); // CHECK-EXEC: {5.00}
+
+  auto fn10_dx = clad::differentiate(fn10, "params[0]");
+  d_param = fn10_dx.execute(params, constants);
+  printf("{%.2f}\n", d_param); // CHECK-EXEC: {5.00}
 }
 
 // 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) {