[llvm] [SandboxIR] Remove tight-coupling with LLVM's SwitchInst::CaseHandle (PR #167093)

[via llvm-commits]

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@@ -1884,45 +1884,96 @@ class SwitchInst : public SingleLLVMInstructionImpl<llvm::SwitchInst> {
     return cast<llvm::SwitchInst>(Val)->getNumCases();
   }
 
-  using CaseHandle =
-      llvm::SwitchInst::CaseHandleImpl<SwitchInst, ConstantInt, BasicBlock>;
-  using ConstCaseHandle =
-      llvm::SwitchInst::CaseHandleImpl<const SwitchInst, const ConstantInt,
-                                       const BasicBlock>;
-  using CaseIt = llvm::SwitchInst::CaseIteratorImpl<CaseHandle>;
-  using ConstCaseIt = llvm::SwitchInst::CaseIteratorImpl<ConstCaseHandle>;
+  class CaseIt;
+  class CaseHandle {
+    Context &Ctx;
+    llvm::SwitchInst::CaseIt LLVMCaseIt;
+    friend class CaseIt;
+
+  public:
+    CaseHandle(Context &Ctx, llvm::SwitchInst::CaseIt LLVMCaseIt)
+        : Ctx(Ctx), LLVMCaseIt(LLVMCaseIt) {}
+    LLVM_ABI ConstantInt *getCaseValue() const;
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vporpo wrote:

These are annotations for dll shared libraries if I am not mistaken (see https://llvm.org/docs/InterfaceExportAnnotations.html#llvm-shared-library). I think it's added to declarations that are defined in the .cpp file, so `llvm::SwitchInst::CaseHandleImpl` wouldn't need them (oh and I just noticed that it's missing from getCaseValue()). Or maybe we can just ignore them and let the folks who maintain these take care of them.

https://github.com/llvm/llvm-project/pull/167093