Add a GVN dependency 'GC' for garbage collection.

This will be used by incoming architecture specific optimizations. The
dependencies must be conservative. When an HInstruction is created we
may not be sure whether it can trigger GC. In that case the
'ChangesGC' dependency must be set. We control at code-generation time
that HInstructions that can call have the 'ChangesGC' dependency
set.

Change-Id: Iea6a7f430009f37a9599b0a0039207049906e45d

1 files changed, 6 insertions, 1 deletions

diff --git a/compiler/optimizing/gvn_test.cc b/compiler/optimizing/gvn_test.cc
index 5c6239b3f9..42ef3ff4a5 100644
--- a/compiler/optimizing/gvn_test.cc
+++ b/compiler/optimizing/gvn_test.cc
@@ -266,6 +266,8 @@ TEST(GVNTest, LoopSideEffects) {
   ArenaPool pool;
   ArenaAllocator allocator(&pool);
 
+  static const SideEffects kCanTriggerGC = SideEffects::CanTriggerGC();
+
   HGraph* graph = CreateGraph(&allocator);
   HBasicBlock* entry = new (&allocator) HBasicBlock(graph);
   graph->AddBlock(entry);
@@ -309,7 +311,7 @@ TEST(GVNTest, LoopSideEffects) {
   ASSERT_TRUE(inner_loop_header->GetLoopInformation()->IsIn(
       *outer_loop_header->GetLoopInformation()));
 
-  // Check that the loops don't have side effects.
+  // Check that the only side effect of loops is to potentially trigger GC.
   {
     // Make one block with a side effect.
     entry->AddInstruction(new (&allocator) HInstanceFieldSet(parameter,
@@ -327,6 +329,8 @@ TEST(GVNTest, LoopSideEffects) {
     ASSERT_FALSE(side_effects.GetBlockEffects(outer_loop_body).DoesAnyWrite());
     ASSERT_FALSE(side_effects.GetLoopEffects(outer_loop_header).DoesAnyWrite());
     ASSERT_FALSE(side_effects.GetLoopEffects(inner_loop_header).DoesAnyWrite());
+    ASSERT_TRUE(side_effects.GetLoopEffects(outer_loop_header).Equals(kCanTriggerGC));
+    ASSERT_TRUE(side_effects.GetLoopEffects(inner_loop_header).Equals(kCanTriggerGC));
   }
 
   // Check that the side effects of the outer loop does not affect the inner loop.
@@ -348,6 +352,7 @@ TEST(GVNTest, LoopSideEffects) {
     ASSERT_TRUE(side_effects.GetBlockEffects(outer_loop_body).DoesAnyWrite());
     ASSERT_TRUE(side_effects.GetLoopEffects(outer_loop_header).DoesAnyWrite());
     ASSERT_FALSE(side_effects.GetLoopEffects(inner_loop_header).DoesAnyWrite());
+    ASSERT_TRUE(side_effects.GetLoopEffects(inner_loop_header).Equals(kCanTriggerGC));
   }
 
   // Check that the side effects of the inner loop affects the outer loop.