[llvm] [SandboxIR] Adds BasicBlock and adds functionality to Function and Context (PR #97637)

[via llvm-commits]

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@@ -205,6 +210,53 @@ class Constant : public sandboxir::User {
 #endif
 };
 
+/// The BasicBlock::iterator.
+class BBIterator {
+public:
+  using difference_type = std::ptrdiff_t;
+  using value_type = Instruction;
+  using pointer = value_type *;
+  using reference = value_type &;
+  using iterator_category = std::bidirectional_iterator_tag;
+
+private:
+  llvm::BasicBlock *BB;
+  llvm::BasicBlock::iterator It;
+  Context *Ctx;
+  pointer getI(llvm::BasicBlock::iterator It) const;
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vporpo wrote:

Renamed it to `getInstr()`.

https://github.com/llvm/llvm-project/pull/97637