Merge pull request #37934 from atrick/disable-weakwarn

Disable weak reference lifetime warnings by default.

Author: atrick

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -154,8 +154,12 @@ static void addMandatoryDiagnosticOptPipeline(SILPassPipelinePlan &P) {
   P.addDiagnoseInfiniteRecursion();
   P.addYieldOnceCheck();
   P.addEmitDFDiagnostics();
-  P.addDiagnoseLifetimeIssues();
 
+  // Only issue weak lifetime warnings for users who select object lifetime
+  // optimization. The risk of spurious warnings outweighs the benefits.
+  if (P.getOptions().EnableCopyPropagation) {
+    P.addDiagnoseLifetimeIssues();
+  }
   // Canonical swift requires all non cond_br critical edges to be split.
   P.addSplitNonCondBrCriticalEdges();
 }

test/SILOptimizer/definite_init_diagnostics.swift

@@ -106,7 +106,7 @@ func test2() {
   weak var w1 : SomeClass?
   _ = w1                // ok: default-initialized
 
-  // expected-warning@+4 {{weak reference will always be nil because the referenced object is deallocated here}}
+  // Note: with -enable-copy-propagation, we also expect: {{weak reference will always be nil because the referenced object is deallocated here}}
   // expected-warning@+3 {{instance will be immediately deallocated because variable 'w2' is 'weak'}}
   // expected-note@+2 {{a strong reference is required to prevent the instance from being deallocated}}
   // expected-note@+1 {{'w2' declared here}}
@@ -1336,7 +1336,7 @@ func testDontDiagnoseUnownedImmediateDeallocationThroughStrong() {
   weak var c1: SomeClass?
   do {
     let tmp = SomeClass()
-    c1 = tmp // expected-warning {{weak reference will always be nil because the referenced object is deallocated here}}
+    c1 = tmp // Note: with -enable-copy-propagation, we also expect: {{weak reference will always be nil because the referenced object is deallocated here}}
   }
 
   unowned let c2: SomeClass
@@ -1347,7 +1347,7 @@ func testDontDiagnoseUnownedImmediateDeallocationThroughStrong() {
 
   weak var c3: SomeClass?
   let c3Tmp = SomeClass()
-  c3 = c3Tmp // expected-warning {{weak reference will always be nil because the referenced object is deallocated here}}
+  c3 = c3Tmp // Note: with -enable-copy-propagation, we also expect: {{weak reference will always be nil because the referenced object is deallocated here}}
 
   unowned let c4: SomeClass
   let c4Tmp = SomeClass()

test/SILOptimizer/diagnose_lifetime_issues.sil

@@ -1,4 +1,4 @@
-// RUN: %target-sil-opt -enable-sil-verify-all %s -diagnose-lifetime-issues  -o /dev/null -verify
+// RUN: %target-sil-opt -enable-sil-verify-all %s -diagnose-lifetime-issues -o /dev/null -verify
 
 import Builtin
 import Swift

test/SILOptimizer/diagnose_lifetime_issues.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend -emit-sil %s -o /dev/null -verify
+// RUN: %target-swift-frontend -emit-sil -enable-copy-propagation %s -o /dev/null -verify
 
 class Delegate {
   func foo() { }

test/SILOptimizer/diagnose_lifetime_issues_objc.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend -emit-sil %s -o /dev/null -verify
+// RUN: %target-swift-frontend -emit-sil %s -enable-copy-propagation -o /dev/null -verify
 // REQUIRES: objc_interop
 
 import Foundation