[llvm] [SandboxIR] Add more Instruction member functions (PR #98588)

[via llvm-commits]

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@@ -262,6 +262,113 @@ const char *Instruction::getOpcodeName(Opcode Opc) {
   llvm_unreachable("Unknown Opcode");
 }
 
+llvm::Instruction *Instruction::getTopmostLLVMInstruction() const {
+  Instruction *Prev = getPrevNode();
+  if (Prev == nullptr) {
+    // If at top of the BB, return the first BB instruction.
+    return &*cast<llvm::BasicBlock>(getParent()->Val)->begin();
+  }
+  // Else get the Previous sandbox IR instruction's bottom IR instruction and
+  // return its successor.
+  llvm::Instruction *PrevBotI = cast<llvm::Instruction>(Prev->Val);
+  return PrevBotI->getNextNode();
+}
+
+BBIterator Instruction::getIterator() const {
+  auto *I = cast<llvm::Instruction>(Val);
+  return BasicBlock::iterator(I->getParent(), I->getIterator(), &Ctx);
+}
+
+Instruction *Instruction::getNextNode() const {
+  assert(getParent() != nullptr && "Detached!");
+  assert(getIterator() != getParent()->end() && "Already at end!");
+  auto *LLVMI = cast<llvm::Instruction>(Val);
+  assert(LLVMI->getParent() != nullptr && "LLVM IR instr is detached!");
+  auto *NextLLVMI = LLVMI->getNextNode();
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vporpo wrote:

Ah the confusing part is that `Val` always points to the bottom LLVM Instruction of a `sandboxir::Instruction`, not the topmost one.
So if `this` is a multi-instruction, `LLVMI` is the bottom-most LLVM Instruction in `this`, so `LLVMI->getNextNode()` points to an LLVM instruction that does **not** belong to `this`, but instead to the next `sandboxir::Instruction`.

https://github.com/llvm/llvm-project/pull/98588