Merge pull request #72985 from eeckstein/fix-diagnose-unreachable

DiagnoseUnreachable: consider borrowed-from instructions when deleting block arguments

Author: eeckstein

lib/SILOptimizer/Mandatory/DiagnoseUnreachable.cpp

@@ -24,6 +24,7 @@
 #include "swift/SIL/SILUndef.h"
 #include "swift/SIL/TerminatorUtils.h"
 #include "swift/SIL/BasicBlockDatastructures.h"
+#include "swift/SIL/OwnershipUtils.h"
 #include "swift/SILOptimizer/PassManager/Passes.h"
 #include "swift/SILOptimizer/PassManager/Transforms.h"
 #include "swift/SILOptimizer/Utils/BasicBlockOptUtils.h"
@@ -190,7 +191,12 @@ static void propagateBasicBlockArgs(SILBasicBlock &BB) {
     SILArgument *Arg = *AI;
 
     // We were able to fold, so all users should use the new folded value.
-    Arg->replaceAllUsesWith(Args[Idx]);
+    if (auto *bfi = getBorrowedFromUser(Arg)) {
+      bfi->replaceAllUsesWith(Args[Idx]);
+      bfi->eraseFromParent();
+    } else {
+      Arg->replaceAllUsesWith(Args[Idx]);
+    }
     ++NumBasicBlockArgsPropagated;
   }
 

test/SILOptimizer/diagnose_unreachable.sil

@@ -1,4 +1,4 @@
-// RUN: %target-sil-opt -enable-sil-verify-all %s -diagnose-unreachable -sil-print-debuginfo | %FileCheck %s
+// RUN: %target-sil-opt -enable-sil-verify-all %s -update-borrowed-from -diagnose-unreachable -sil-print-debuginfo | %FileCheck %s
 
 import Builtin
 import Swift