[llvm] [InstCombine] If inst in unreachable refers to an inst change it to poison (#65107) (PR #78444)

[Nikita Popov via llvm-commits]

================
@@ -2770,15 +2770,31 @@ bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To,
   return false;
 }
 
+void llvm::handleUnreachableTerminator(Instruction *I) {
+  // RemoveDIs: erase debug-info on this instruction manually.
+  I->dropDbgValues();
+  unsigned Opcode = I->getOpcode();
+  if (Opcode >= Instruction::Ret && Opcode <= Instruction::Invoke &&
+      I->getNumOperands() > 0) {
+    unsigned OpNum = isa<InvokeInst>(I) ? I->getNumOperands() - 1 : 0;
----------------
nikic wrote:

You should loop over `I->operands()` here, not only update a single operand.

https://github.com/llvm/llvm-project/pull/78444