optimizing: do not illegally remove constructor barriers after inlining

Remove the illegal optimization that destroyed constructor barriers
after inlining invoke-super constructor calls.

---

According to JLS 7.5.1,

"Note that if one constructor invokes another constructor, and the
invoked constructor sets a final field, the freeze for the final field
takes place at the end of the invoked constructor."

This means if an object is published (stored to a location potentially
visible to another thread) inside of an outer constructor, all final
field stores from any inner constructors must be visible to other
threads.

Test: art/test.py
Bug: 37001605
Change-Id: I3b55f6c628ff1773dab88022a6475d50a1a6f906

1 files changed, 8 insertions, 6 deletions

diff --git a/compiler/optimizing/instruction_builder.cc b/compiler/optimizing/instruction_builder.cc
index 88f67fae04..978c6a2d71 100644
--- a/compiler/optimizing/instruction_builder.cc
+++ b/compiler/optimizing/instruction_builder.cc
@@ -589,6 +589,11 @@ void HInstructionBuilder::Binop_22b(const Instruction& instruction, bool reverse
 }
 
 static bool RequiresConstructorBarrier(const DexCompilationUnit* cu, CompilerDriver* driver) {
+  // Can be null in unit tests only.
+  if (UNLIKELY(cu == nullptr)) {
+    return false;
+  }
+
   Thread* self = Thread::Current();
   return cu->IsConstructor()
       && driver->RequiresConstructorBarrier(self, cu->GetDexFile(), cu->GetClassDefIndex());
@@ -634,12 +639,9 @@ void HInstructionBuilder::BuildReturn(const Instruction& instruction,
                                       Primitive::Type type,
                                       uint32_t dex_pc) {
   if (type == Primitive::kPrimVoid) {
-    if (graph_->ShouldGenerateConstructorBarrier()) {
-      // The compilation unit is null during testing.
-      if (dex_compilation_unit_ != nullptr) {
-        DCHECK(RequiresConstructorBarrier(dex_compilation_unit_, compiler_driver_))
-          << "Inconsistent use of ShouldGenerateConstructorBarrier. Should not generate a barrier.";
-      }
+    // This may insert additional redundant constructor fences from the super constructors.
+    // TODO: remove redundant constructor fences (b/36656456).
+    if (RequiresConstructorBarrier(dex_compilation_unit_, compiler_driver_)) {
       AppendInstruction(new (arena_) HMemoryBarrier(kStoreStore, dex_pc));
     }
     AppendInstruction(new (arena_) HReturnVoid(dex_pc));