From 9461931d68a1024cecdc5f5ab28fe51bf04922fb Mon Sep 17 00:00:00 2001
From: ToshitJain <toshit3q34@gmail.com>
Date: Sun, 22 Dec 2024 22:52:59 +0530
Subject: [PATCH] Fix for Parenthesis issue in gradients

---
 include/clad/Differentiator/VisitorBase.h |  9 ++++++++-
 lib/Differentiator/VisitorBase.cpp        | 23 +++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/clad/Differentiator/VisitorBase.h b/include/clad/Differentiator/VisitorBase.h
index 0abd868ca..ab6ed2b4c 100644
--- a/include/clad/Differentiator/VisitorBase.h
+++ b/include/clad/Differentiator/VisitorBase.h
@@ -275,7 +275,14 @@ namespace clad {
     /// either LHS or RHS is null.
     clang::Expr* BuildOp(clang::BinaryOperatorKind OpCode, clang::Expr* L,
                          clang::Expr* R, clang::SourceLocation OpLoc = noLoc);
-
+    /// Recursive Function to resolve Unary Minus. If the leftmost operand
+    /// has a Unary Minus then does not add the operator else adds.
+    /// Also resolves multiple Unary Minus. Example : (-(-(-2))) gives -2.
+    /// \param[in] E Expression fed to the recursive call.
+    /// \param[in] OpLoc Location to add Unary Minus if needed.
+    /// \returns Expression with correct Unary Operator placement.
+    clang::Expr* RemoveFirstUnaryMinus(clang::Expr* E,
+                                       clang::SourceLocation OpLoc);
     clang::Expr* BuildParens(clang::Expr* E);
     /// Builds variable declaration to be used inside the derivative
     /// body.
diff --git a/lib/Differentiator/VisitorBase.cpp b/lib/Differentiator/VisitorBase.cpp
index 408dd9f91..dea78ddf0 100644
--- a/lib/Differentiator/VisitorBase.cpp
+++ b/lib/Differentiator/VisitorBase.cpp
@@ -400,8 +400,31 @@ namespace clad {
     // Debug clang requires the location to be valid
     if (!OpLoc.isValid())
       OpLoc = utils::GetValidSLoc(m_Sema);
+    // Call function for UnaryMinus
+    if (OpCode == UO_Minus)
+      return RemoveFirstUnaryMinus(E->IgnoreCasts(), OpLoc);
     return m_Sema.BuildUnaryOp(nullptr, OpLoc, OpCode, E).get();
   }
+  Expr* VisitorBase::RemoveFirstUnaryMinus(Expr* E, SourceLocation OpLoc) {
+    if (auto* UO = llvm::dyn_cast<UnaryOperator>(E)) {
+      if (UO->getOpcode() == UO_Minus)
+        return UO->getSubExpr();
+    }
+    if (auto* BO = llvm::dyn_cast<BinaryOperator>(E)) {
+      if (BO->getOpcode() == BO_Mul || BO->getOpcode() == BO_Div) {
+        Expr* LHS = BO->getLHS();
+        Expr* RHS = BO->getRHS();
+        Expr* LHSModified = RemoveFirstUnaryMinus(LHS->IgnoreCasts(), OpLoc);
+        SourceLocation BO_loc = BO->getExprLoc();
+        return m_Sema
+            .BuildBinOp(nullptr, BO_loc, BO->getOpcode(), LHSModified, RHS)
+            .get();
+      }
+    }
+    if (!OpLoc.isValid())
+      OpLoc = utils::GetValidSLoc(m_Sema);
+    return m_Sema.BuildUnaryOp(nullptr, OpLoc, UO_Minus, E).get();
+  }
 
   Expr* VisitorBase::BuildOp(clang::BinaryOperatorKind OpCode, Expr* L, Expr* R,
                              SourceLocation OpLoc) {