[llvm] Add functions peekNextN(unsigned) and assignNewExpr(ArrayRef<uint64_t>) to DIExpressionCursor (PR #71717)

[Shubham Sandeep Rastogi via llvm-commits]

https://github.com/rastogishubham updated https://github.com/llvm/llvm-project/pull/71717

>From 5ecdba8a678af0752733744bbe6f91c3c4718c16 Mon Sep 17 00:00:00 2001
From: Shubham Sandeep Rastogi <srastogi22 at apple.com>
Date: Wed, 1 Nov 2023 17:25:26 -0700
Subject: [PATCH] Add functions peekNextN(unsigned) and
 assignNewExpr(ArrayRef<uint64_t>) to DIExpressionCursor

This commit adds two functions to the DIExpressionCursor class.

peekNextN(unsigned) works like peekNext, but lets you peek the next Nth
element

assignNewExpr(ArrayRef<uint64_t>) lets you assign a new expression to
the same DIExpressionCursor object
---
 llvm/include/llvm/IR/DebugInfoMetadata.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index a1c554677f8bf..555bd623ad9ef 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -3199,6 +3199,23 @@ class DIExpressionCursor {
     return *Next;
   }
 
+  std::optional<DIExpression::ExprOperand> peekNextN(unsigned N) const {
+    if (Start == End)
+      return std::nullopt;
+    DIExpression::expr_op_iterator Nth = Start;
+    for (unsigned I = 0; I < N; I++) {
+      Nth = Nth.getNext();
+      if (Nth == End)
+        return std::nullopt;
+    }
+    return *Nth;
+  }
+
+  void assignNewExpr(ArrayRef<uint64_t> Expr) {
+    this->Start = DIExpression::expr_op_iterator(Expr.begin());
+    this->End = DIExpression::expr_op_iterator(Expr.end());
+  }
+
   /// Determine whether there are any operations left in this expression.
   operator bool() const { return Start != End; }