ART: Fix single-preheader transformation.
Original implementation of "Make sure the loop has only one
pre-header" had an assumption that the header had no phi
functions since loops with multiple preheaders now only may exist
during graph building before ssa construction; all of the
optimizations preserve the single-preheader invariant. This code is
used by DCE; DCE was called multiple times but after graph building
preheader transformation was never executed. However if someone
introduces a optimization which might not keep the invariant
(e.g. loop peeling) the data flow adjustments must be performed.
Test: loop_optimization_test.cc
Test: test-art-target, test-art-host
Change-Id: I88bb0aad2dd5241addef7fe9cda474a6868bf532
diff --git a/compiler/optimizing/loop_optimization_test.cc b/compiler/optimizing/loop_optimization_test.cc
index 4e1857d..db83689 100644
--- a/compiler/optimizing/loop_optimization_test.cc
+++ b/compiler/optimizing/loop_optimization_test.cc
@@ -194,7 +194,9 @@
// Check that SimplifyLoop() doesn't invalidate data flow when ordering loop headers'
// predecessors.
-TEST_F(LoopOptimizationTest, SimplifyLoop) {
+//
+// This is a test for nodes.cc functionality - HGraph::SimplifyLoop.
+TEST_F(LoopOptimizationTest, SimplifyLoopReoderPredecessors) {
// Can't use AddLoop as we want special order for blocks predecessors.
HBasicBlock* header = new (GetAllocator()) HBasicBlock(graph_);
HBasicBlock* body = new (GetAllocator()) HBasicBlock(graph_);
@@ -232,4 +234,83 @@
ASSERT_TRUE(input->GetBlock()->Dominates(header->GetPredecessors()[i]));
}
}
+
+// Test that SimplifyLoop() processes the multiple-preheaders loops correctly.
+//
+// This is a test for nodes.cc functionality - HGraph::SimplifyLoop.
+TEST_F(LoopOptimizationTest, SimplifyLoopSinglePreheader) {
+ HBasicBlock* header = AddLoop(entry_block_, return_block_);
+
+ header->InsertInstructionBefore(
+ new (GetAllocator()) HSuspendCheck(), header->GetLastInstruction());
+
+ // Insert an if construct before the loop so it will have two preheaders.
+ HBasicBlock* if_block = new (GetAllocator()) HBasicBlock(graph_);
+ HBasicBlock* preheader0 = new (GetAllocator()) HBasicBlock(graph_);
+ HBasicBlock* preheader1 = new (GetAllocator()) HBasicBlock(graph_);
+
+ graph_->AddBlock(if_block);
+ graph_->AddBlock(preheader0);
+ graph_->AddBlock(preheader1);
+
+ // Fix successors/predecessors.
+ entry_block_->ReplaceSuccessor(header, if_block);
+ if_block->AddSuccessor(preheader0);
+ if_block->AddSuccessor(preheader1);
+ preheader0->AddSuccessor(header);
+ preheader1->AddSuccessor(header);
+
+ if_block->AddInstruction(new (GetAllocator()) HIf(parameter_));
+ preheader0->AddInstruction(new (GetAllocator()) HGoto());
+ preheader1->AddInstruction(new (GetAllocator()) HGoto());
+
+ HBasicBlock* body = header->GetSuccessors()[0];
+ DCHECK(body != return_block_);
+
+ // Add some data flow.
+ HIntConstant* const_0 = graph_->GetIntConstant(0);
+ HIntConstant* const_1 = graph_->GetIntConstant(1);
+ HIntConstant* const_2 = graph_->GetIntConstant(2);
+
+ HAdd* preheader0_add = new (GetAllocator()) HAdd(DataType::Type::kInt32, parameter_, const_0);
+ preheader0->AddInstruction(preheader0_add);
+ HAdd* preheader1_add = new (GetAllocator()) HAdd(DataType::Type::kInt32, parameter_, const_1);
+ preheader1->AddInstruction(preheader1_add);
+
+ HPhi* header_phi = new (GetAllocator()) HPhi(GetAllocator(), 0, 0, DataType::Type::kInt32);
+ header->AddPhi(header_phi);
+
+ HAdd* body_add = new (GetAllocator()) HAdd(DataType::Type::kInt32, parameter_, const_2);
+ body->AddInstruction(body_add);
+
+ DCHECK(header->GetPredecessors()[0] == body);
+ DCHECK(header->GetPredecessors()[1] == preheader0);
+ DCHECK(header->GetPredecessors()[2] == preheader1);
+
+ header_phi->AddInput(body_add);
+ header_phi->AddInput(preheader0_add);
+ header_phi->AddInput(preheader1_add);
+
+ graph_->ClearLoopInformation();
+ graph_->ClearDominanceInformation();
+ graph_->BuildDominatorTree();
+
+ EXPECT_EQ(header->GetPredecessors().size(), 2u);
+ EXPECT_EQ(header->GetPredecessors()[1], body);
+
+ HBasicBlock* new_preheader = header->GetLoopInformation()->GetPreHeader();
+ EXPECT_EQ(preheader0->GetSingleSuccessor(), new_preheader);
+ EXPECT_EQ(preheader1->GetSingleSuccessor(), new_preheader);
+
+ EXPECT_EQ(new_preheader->GetPhis().CountSize(), 1u);
+ HPhi* new_preheader_phi = new_preheader->GetFirstPhi()->AsPhi();
+ EXPECT_EQ(new_preheader_phi->InputCount(), 2u);
+ EXPECT_EQ(new_preheader_phi->InputAt(0), preheader0_add);
+ EXPECT_EQ(new_preheader_phi->InputAt(1), preheader1_add);
+
+ EXPECT_EQ(header_phi->InputCount(), 2u);
+ EXPECT_EQ(header_phi->InputAt(0), new_preheader_phi);
+ EXPECT_EQ(header_phi->InputAt(1), body_add);
+}
+
} // namespace art