[llvm] Remove the optional bitcast between a musttail call and its ret (PR #201280)

[Matt Arsenault via llvm-commits]

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@@ -7132,6 +7132,20 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
       }
     }
 
+    // Old bitcode allowed an optional bitcast between a musttail call and the
+    // return. Under opaque pointers that cast is always a no-op, and the
+    // verifier no longer accepts it, so drop it.
+    if (auto *BC = dyn_cast<BitCastInst>(&I);
+        BC && BC->getSrcTy() == BC->getDestTy() &&
+        isa_and_nonnull<ReturnInst>(BC->getNextNode())) {
+      if (auto *CI = dyn_cast<CallInst>(BC->getOperand(0));
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arsenm wrote:

I'd expect this to start at the call, not the bitcast? 

https://github.com/llvm/llvm-project/pull/201280