[llvm] [SandboxIR] Implement the InsertElementInst class (PR #102404)

[via llvm-commits]

================
@@ -753,6 +755,48 @@ class SelectInst : public Instruction {
 #endif
 };
 
+class InsertElementInst final : public Instruction {
+  /// Use Context::createInsertElementInst(). Don't call
+  /// the constructor directly.
+  InsertElementInst(llvm::Instruction *I, Context &Ctx)
+      : Instruction(ClassID::InsertElement, Opcode::InsertElement, I, Ctx) {}
+  InsertElementInst(ClassID SubclassID, llvm::Instruction *I, Context &Ctx)
+      : Instruction(SubclassID, Opcode::InsertElement, I, Ctx) {}
+  friend class Context; // For accessing the constructor in
+                        // create*()
+  Use getOperandUseInternal(unsigned OpIdx, bool Verify) const final {
+    return getOperandUseDefault(OpIdx, Verify);
+  }
+  SmallVector<llvm::Instruction *, 1> getLLVMInstrs() const final {
+    return {cast<llvm::Instruction>(Val)};
+  }
+
+public:
+  static Value *create(Value *Vec, Value *NewElt, Value *Idx,
+                       Instruction *InsertBefore, Context &Ctx,
+                       const Twine &Name = "");
+  static Value *create(Value *Vec, Value *NewElt, Value *Idx,
+                       BasicBlock *InsertAtEnd, Context &Ctx,
+                       const Twine &Name = "");
+  static bool classof(const Value *From) {
----------------
vporpo wrote:

Could you also add a test for this? Something like:
```
EXPECT_EQ(sandboxir::InsertElementInst::isValidOperands(V1, V2, V3), llvm::InsertElementInst::isValidOperands(Ctx.getValue(V1), Ctx.getValue(V2), Ctx.getValue(V3)));
```

https://github.com/llvm/llvm-project/pull/102404