Merge pull request #25007 from gottesmm/pr-d77fff3d54f2b70d825402ebfd766d3891da9b0b

[diagnose-unreachable] Ignore/eliminate end_borrows after noreturn fu…

Author: gottesmm

lib/SILOptimizer/Mandatory/DiagnoseUnreachable.cpp

@@ -529,15 +529,20 @@ static bool simplifyBlocksWithCallsToNoReturn(SILBasicBlock &BB,
       // Diagnose the unreachable code within the same block as the call to
       // noreturn.
       if (isUserCode(CurrentInst) && !DiagnosedUnreachableCode) {
-        if (NoReturnCall->getLoc().is<RegularLocation>()) {
-          if (!NoReturnCall->getLoc().isASTNode<ExplicitCastExpr>()) {
-            diagnose(BB.getModule().getASTContext(),
-                     CurrentInst->getLoc().getSourceLoc(),
-                     diag::unreachable_code);
-            diagnose(BB.getModule().getASTContext(),
-                     NoReturnCall->getLoc().getSourceLoc(),
-                     diag::call_to_noreturn_note);
-            DiagnosedUnreachableCode = true;
+        // If we have an instruction that is an end_borrow, ignore it. This
+        // happens when passing a guaranteed argument through generic code paths
+        // to no return functions.
+        if (!isa<EndBorrowInst>(CurrentInst)) {
+          if (NoReturnCall->getLoc().is<RegularLocation>()) {
+            if (!NoReturnCall->getLoc().isASTNode<ExplicitCastExpr>()) {
+              diagnose(BB.getModule().getASTContext(),
+                       CurrentInst->getLoc().getSourceLoc(),
+                       diag::unreachable_code);
+              diagnose(BB.getModule().getASTContext(),
+                       NoReturnCall->getLoc().getSourceLoc(),
+                       diag::call_to_noreturn_note);
+              DiagnosedUnreachableCode = true;
+            }
           }
         }
       }

test/SILOptimizer/return_ownership.swift

@@ -0,0 +1,17 @@
+// RUN: %target-swift-frontend %s -enable-ownership-stripping-after-serialization -emit-sil -verify
+
+class TuringMachine {
+  func halt() -> Never {
+    repeat { } while true
+  }
+}
+
+func diagnose_missing_return_no_error_after_noreturn_method() -> Int {
+  TuringMachine().halt()
+} // no error
+
+func testUnreachableAfterNoReturnMethod() -> Int {
+  TuringMachine().halt(); // expected-note{{a call to a never-returning function}}
+  return 0; // expected-warning {{will never be executed}}
+}
+