Merge pull request #77044 from nate-chandler/rdar137960229

[DiagnoseUnreachable] Ignore dead_end destroys.

Author: nate-chandler

lib/SILOptimizer/Mandatory/DiagnoseUnreachable.cpp

@@ -775,6 +775,14 @@ static bool simplifyBlocksWithCallsToNoReturn(SILBasicBlock &BB,
     if (isa<EndBorrowInst>(currInst))
       return false;
 
+    // destroy_value [dead_end] instructions are inserted at the availability
+    // boundary by lifetime completion.  Such instructions correctly mark the
+    // lifetime boundary of the destroyed value and never arise from dead user
+    // code.
+    auto *dvi = dyn_cast<DestroyValueInst>(currInst);
+    if (dvi && dvi->isDeadEnd())
+      return false;
+
     // If no-return instruction is not something we can point in code or
     // it's an explicit cast, skip it.
     if (!noReturnCall->getLoc().is<RegularLocation>() ||

validation-test/SILOptimizer/rdar137960229.swift

@@ -0,0 +1,9 @@
+// RUN: %target-swift-frontend -c %s -verify
+
+func testFatalError(_ message: @autoclosure () -> String = String()) -> Never {
+  Swift.fatalError()
+}
+
+func test() {
+  testFatalError()
+}