Merge pull request #4453 from trentxintong/LLVMSwiftARC

Fix a globalvariable initializer bug in LLVMSwiftARC

Author: trentxintong

lib/LLVMPasses/LLVMARCOpts.cpp

@@ -545,8 +545,10 @@ static DtorKind analyzeDestructor(Value *P) {
 
   // We have to have a known heap metadata value, reject dynamically computed
   // ones, or places
+  // Also, make sure we have a definitive initializer for the global.
   GlobalVariable *GV = dyn_cast<GlobalVariable>(P->stripPointerCasts());
-  if (GV == 0 || GV->mayBeOverridden()) return DtorKind::Unknown;
+  if (GV == 0 || !GV->hasDefinitiveInitializer())
+    return DtorKind::Unknown;
 
   ConstantStruct *CS = dyn_cast_or_null<ConstantStruct>(GV->getInitializer());
   if (CS == 0 || CS->getNumOperands() == 0) return DtorKind::Unknown;

test/LLVMPasses/allocation-deletion.ll

@@ -81,4 +81,19 @@ entry:
 ; CHECK-NEXT: ret void
 
 
+; external_dtor_alloc_eliminate -  Make sure we can not eliminate the allocation
+; because we know nothing about the type of the allocation.
+@external_dtor_metadata = external global %swift.heapmetadata, align 8
+define void @external_dtor_alloc_eliminate() nounwind {
+entry:
+  %0 = tail call noalias %swift.refcounted* @swift_allocObject(%swift.heapmetadata* nonnull @external_dtor_metadata, i64 24, i64 8) nounwind
+  tail call void @swift_release(%swift.refcounted* %0) nounwind
+  ret void
+}
+
+; CHECK: @external_dtor_alloc_eliminate
+; CHECK-NEXT: entry:
+; CHECK-NEXT: swift_allocObject
+; CHECK-NEXT: swift_release
+; CHECK-NEXT: ret void