[llvm] [Reg2Mem] Handle CallBr instructions (PR #90953)

[via llvm-commits]

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@@ -102,9 +102,12 @@ AllocaInst *llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads,
         new StoreInst(&I, Slot, Handler->getFirstInsertionPt());
       return Slot;
     }
+  } else if (InvokeInst *II = dyn_cast<InvokeInst>(&I)) {
+    InsertPt = II->getNormalDest()->getFirstInsertionPt();
+  } else if (CallBrInst *CBI = dyn_cast<CallBrInst>(&I)) {
+    InsertPt = CBI->getDefaultDest()->getFirstInsertionPt();
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XChy wrote:

Why? As the langref says:
> The output values of a ‘callbr’ instruction are available only to the ‘fallthrough’ block, not to any ‘indirect’ blocks(s).

https://github.com/llvm/llvm-project/pull/90953