[llvm] [NFC] Add DIExpression::extractLeadingOffset (PR #97719)

[Orlando Cazalet-Hyams via llvm-commits]

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@@ -2982,6 +2982,16 @@ class DIExpression : public MDNode {
   /// return true with an offset of zero.
   bool extractIfOffset(int64_t &Offset) const;
 
+  /// Assuming that the expression operates on an address, extract a constant
+  /// offset and the succsessive ops. Return false if the expression contains
+  /// any incompatible ops (including non-zero DW_OP_LLVM_args - only a single
+  /// address operand to the expression is permitted).
+  ///
+  /// We don't try very hard to interpret the expression because we assume that
+  /// foldConstantMath has canonicalized the expression.
+  bool extractLeadingOffset(int64_t &Offset,
+                            SmallVectorImpl<uint64_t> &RemainingOps) const;
+
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OCHyams wrote:

note to self: rename `Offset` to `OffsetInBytes`

https://github.com/llvm/llvm-project/pull/97719