Simplify unsigned comparisons against zero (with unit tests).

Rationale: Such cases occurs a lot after dynamic
           bound check optimization (where the lower bound
           is test against upper bound). Removing this
           unnecessary test improves quality of code.

Change-Id: I3e4dc9f9d799aad342e1c344013ac60fcc3073ac

1 files changed, 178 insertions, 54 deletions

diff --git a/compiler/optimizing/constant_folding_test.cc b/compiler/optimizing/constant_folding_test.cc
index 2feb75cc9f..e469c8d6d0 100644
--- a/compiler/optimizing/constant_folding_test.cc
+++ b/compiler/optimizing/constant_folding_test.cc
@@ -29,50 +29,70 @@
 
 namespace art {
 
-static void TestCode(const uint16_t* data,
-                     const std::string& expected_before,
-                     const std::string& expected_after_cf,
-                     const std::string& expected_after_dce,
-                     std::function<void(HGraph*)> check_after_cf,
-                     Primitive::Type return_type = Primitive::kPrimInt) {
-  ArenaPool pool;
-  ArenaAllocator allocator(&pool);
-  HGraph* graph = CreateCFG(&allocator, data, return_type);
-  ASSERT_NE(graph, nullptr);
-
-  graph->TryBuildingSsa();
-
-  StringPrettyPrinter printer_before(graph);
-  printer_before.VisitInsertionOrder();
-  std::string actual_before = printer_before.str();
-  ASSERT_EQ(expected_before, actual_before);
-
-  std::unique_ptr<const X86InstructionSetFeatures> features_x86(
-      X86InstructionSetFeatures::FromCppDefines());
-  x86::CodeGeneratorX86 codegenX86(graph, *features_x86.get(), CompilerOptions());
-  HConstantFolding(graph).Run();
-  SSAChecker ssa_checker_cf(graph);
-  ssa_checker_cf.Run();
-  ASSERT_TRUE(ssa_checker_cf.IsValid());
-
-  StringPrettyPrinter printer_after_cf(graph);
-  printer_after_cf.VisitInsertionOrder();
-  std::string actual_after_cf = printer_after_cf.str();
-  ASSERT_EQ(expected_after_cf, actual_after_cf);
-
-  check_after_cf(graph);
-
-  HDeadCodeElimination(graph).Run();
-  SSAChecker ssa_checker_dce(graph);
-  ssa_checker_dce.Run();
-  ASSERT_TRUE(ssa_checker_dce.IsValid());
-
-  StringPrettyPrinter printer_after_dce(graph);
-  printer_after_dce.VisitInsertionOrder();
-  std::string actual_after_dce = printer_after_dce.str();
-  ASSERT_EQ(expected_after_dce, actual_after_dce);
-}
-
+/**
+ * Fixture class for the constant folding and dce tests.
+ */
+class ConstantFoldingTest : public testing::Test {
+ public:
+  ConstantFoldingTest() : pool_(), allocator_(&pool_) {
+    graph_ = CreateGraph(&allocator_);
+  }
+
+  void TestCode(const uint16_t* data,
+                const std::string& expected_before,
+                const std::string& expected_after_cf,
+                const std::string& expected_after_dce,
+                std::function<void(HGraph*)> check_after_cf,
+                Primitive::Type return_type = Primitive::kPrimInt) {
+    graph_ = CreateCFG(&allocator_, data, return_type);
+    TestCodeOnReadyGraph(expected_before,
+                         expected_after_cf,
+                         expected_after_dce,
+                         check_after_cf);
+  }
+
+  void TestCodeOnReadyGraph(const std::string& expected_before,
+                            const std::string& expected_after_cf,
+                            const std::string& expected_after_dce,
+                            std::function<void(HGraph*)> check_after_cf) {
+    ASSERT_NE(graph_, nullptr);
+    graph_->TryBuildingSsa();
+
+    StringPrettyPrinter printer_before(graph_);
+    printer_before.VisitInsertionOrder();
+    std::string actual_before = printer_before.str();
+    EXPECT_EQ(expected_before, actual_before);
+
+    std::unique_ptr<const X86InstructionSetFeatures> features_x86(
+        X86InstructionSetFeatures::FromCppDefines());
+    x86::CodeGeneratorX86 codegenX86(graph_, *features_x86.get(), CompilerOptions());
+    HConstantFolding(graph_).Run();
+    SSAChecker ssa_checker_cf(graph_);
+    ssa_checker_cf.Run();
+    ASSERT_TRUE(ssa_checker_cf.IsValid());
+
+    StringPrettyPrinter printer_after_cf(graph_);
+    printer_after_cf.VisitInsertionOrder();
+    std::string actual_after_cf = printer_after_cf.str();
+    EXPECT_EQ(expected_after_cf, actual_after_cf);
+
+    check_after_cf(graph_);
+
+    HDeadCodeElimination(graph_).Run();
+    SSAChecker ssa_checker_dce(graph_);
+    ssa_checker_dce.Run();
+    ASSERT_TRUE(ssa_checker_dce.IsValid());
+
+    StringPrettyPrinter printer_after_dce(graph_);
+    printer_after_dce.VisitInsertionOrder();
+    std::string actual_after_dce = printer_after_dce.str();
+    EXPECT_EQ(expected_after_dce, actual_after_dce);
+  }
+
+  ArenaPool pool_;
+  ArenaAllocator allocator_;
+  HGraph* graph_;
+};
 
 /**
  * Tiny three-register program exercising int constant folding on negation.
@@ -84,7 +104,7 @@ static void TestCode(const uint16_t* data,
  *     v1 <- -v0                1.      neg-int v1, v0
  *     return v1                2.      return v1
  */
-TEST(ConstantFolding, IntConstantFoldingNegation) {
+TEST_F(ConstantFoldingTest, IntConstantFoldingNegation) {
   const uint16_t data[] = TWO_REGISTERS_CODE_ITEM(
     Instruction::CONST_4 | 0 << 8 | 1 << 12,
     Instruction::NEG_INT | 1 << 8 | 0 << 12,
@@ -141,7 +161,7 @@ TEST(ConstantFolding, IntConstantFoldingNegation) {
  *     (v2, v3) <- -(v0, v1)    1.      neg-long v2, v0
  *     return (v2, v3)          2.      return-wide v2
  */
-TEST(ConstantFolding, LongConstantFoldingNegation) {
+TEST_F(ConstantFoldingTest, LongConstantFoldingNegation) {
   const int64_t input = INT64_C(4294967296);             // 2^32
   const uint16_t word0 = Low16Bits(Low32Bits(input));    // LSW.
   const uint16_t word1 = High16Bits(Low32Bits(input));
@@ -205,7 +225,7 @@ TEST(ConstantFolding, LongConstantFoldingNegation) {
  *     v2 <- v0 + v1            2.      add-int v2, v0, v1
  *     return v2                4.      return v2
  */
-TEST(ConstantFolding, IntConstantFoldingOnAddition1) {
+TEST_F(ConstantFoldingTest, IntConstantFoldingOnAddition1) {
   const uint16_t data[] = THREE_REGISTERS_CODE_ITEM(
     Instruction::CONST_4 | 0 << 8 | 1 << 12,
     Instruction::CONST_4 | 1 << 8 | 2 << 12,
@@ -271,7 +291,7 @@ TEST(ConstantFolding, IntConstantFoldingOnAddition1) {
  *     v2 <- v0 + v1            6.      add-int v2, v0, v1
  *     return v2                8.      return v2
  */
-TEST(ConstantFolding, IntConstantFoldingOnAddition2) {
+TEST_F(ConstantFoldingTest, IntConstantFoldingOnAddition2) {
   const uint16_t data[] = THREE_REGISTERS_CODE_ITEM(
     Instruction::CONST_4 | 0 << 8 | 1 << 12,
     Instruction::CONST_4 | 1 << 8 | 2 << 12,
@@ -357,7 +377,7 @@ TEST(ConstantFolding, IntConstantFoldingOnAddition2) {
  *     v2 <- v0 - v1            2.      sub-int v2, v0, v1
  *     return v2                4.      return v2
  */
-TEST(ConstantFolding, IntConstantFoldingOnSubtraction) {
+TEST_F(ConstantFoldingTest, IntConstantFoldingOnSubtraction) {
   const uint16_t data[] = THREE_REGISTERS_CODE_ITEM(
     Instruction::CONST_4 | 0 << 8 | 3 << 12,
     Instruction::CONST_4 | 1 << 8 | 2 << 12,
@@ -421,7 +441,7 @@ TEST(ConstantFolding, IntConstantFoldingOnSubtraction) {
  *       (v0, v1) + (v1, v2)    4.      add-long v4, v0, v2
  *     return (v4, v5)          6.      return-wide v4
  */
-TEST(ConstantFolding, LongConstantFoldingOnAddition) {
+TEST_F(ConstantFoldingTest, LongConstantFoldingOnAddition) {
   const uint16_t data[] = SIX_REGISTERS_CODE_ITEM(
     Instruction::CONST_WIDE_16 | 0 << 8, 1,
     Instruction::CONST_WIDE_16 | 2 << 8, 2,
@@ -486,7 +506,7 @@ TEST(ConstantFolding, LongConstantFoldingOnAddition) {
  *       (v0, v1) - (v1, v2)    4.      sub-long v4, v0, v2
  *     return (v4, v5)          6.      return-wide v4
  */
-TEST(ConstantFolding, LongConstantFoldingOnSubtraction) {
+TEST_F(ConstantFoldingTest, LongConstantFoldingOnSubtraction) {
   const uint16_t data[] = SIX_REGISTERS_CODE_ITEM(
     Instruction::CONST_WIDE_16 | 0 << 8, 3,
     Instruction::CONST_WIDE_16 | 2 << 8, 2,
@@ -560,7 +580,7 @@ TEST(ConstantFolding, LongConstantFoldingOnSubtraction) {
  * L3: v2 <- v1 + 8             11.     add-int/lit16 v2, v1, #+8
  *     return v2                13.     return v2
  */
-TEST(ConstantFolding, IntConstantFoldingAndJumps) {
+TEST_F(ConstantFoldingTest, IntConstantFoldingAndJumps) {
   const uint16_t data[] = THREE_REGISTERS_CODE_ITEM(
     Instruction::CONST_4 | 0 << 8 | 1 << 12,
     Instruction::CONST_4 | 1 << 8 | 2 << 12,
@@ -656,7 +676,6 @@ TEST(ConstantFolding, IntConstantFoldingAndJumps) {
            check_after_cf);
 }
 
-
 /**
  * Three-register program with a constant (static) condition.
  *
@@ -670,7 +689,7 @@ TEST(ConstantFolding, IntConstantFoldingAndJumps) {
  * L1: v2 <- v0 + v1            5.      add-int v2, v0, v1
  *     return-void              7.      return
  */
-TEST(ConstantFolding, ConstantCondition) {
+TEST_F(ConstantFoldingTest, ConstantCondition) {
   const uint16_t data[] = THREE_REGISTERS_CODE_ITEM(
     Instruction::CONST_4 | 1 << 8 | 1 << 12,
     Instruction::CONST_4 | 0 << 8 | 0 << 12,
@@ -732,4 +751,109 @@ TEST(ConstantFolding, ConstantCondition) {
            check_after_cf);
 }
 
+/**
+ * Unsigned comparisons with zero. Since these instructions are not present
+ * in the bytecode, we need to set up the graph explicitly.
+ */
+TEST_F(ConstantFoldingTest, UnsignedComparisonsWithZero) {
+  graph_ = CreateGraph(&allocator_);
+  HBasicBlock* entry_block = new (&allocator_) HBasicBlock(graph_);
+  graph_->AddBlock(entry_block);
+  graph_->SetEntryBlock(entry_block);
+  HBasicBlock* block = new (&allocator_) HBasicBlock(graph_);
+  graph_->AddBlock(block);
+  HBasicBlock* exit_block = new (&allocator_) HBasicBlock(graph_);
+  graph_->AddBlock(exit_block);
+  graph_->SetExitBlock(exit_block);
+  entry_block->AddSuccessor(block);
+  block->AddSuccessor(exit_block);
+
+  // Make various unsigned comparisons with zero against a parameter.
+  HInstruction* parameter = new (&allocator_) HParameterValue(
+      graph_->GetDexFile(), 0, 0, Primitive::kPrimInt, true);
+  entry_block->AddInstruction(parameter);
+  HInstruction* zero = graph_->GetIntConstant(0);
+  HInstruction* last;
+  block->AddInstruction(last = new (&allocator_) HAbove(zero, parameter));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+  block->AddInstruction(last = new (&allocator_) HAbove(parameter, zero));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+  block->AddInstruction(last = new (&allocator_) HAboveOrEqual(zero, parameter));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+  block->AddInstruction(last = new (&allocator_) HAboveOrEqual(parameter, zero));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+  block->AddInstruction(last = new (&allocator_) HBelow(zero, parameter));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+  block->AddInstruction(last = new (&allocator_) HBelow(parameter, zero));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+  block->AddInstruction(last = new (&allocator_) HBelowOrEqual(zero, parameter));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+  block->AddInstruction(last = new (&allocator_) HBelowOrEqual(parameter, zero));
+  block->AddInstruction(new (&allocator_) HDeoptimize(last, 0));
+
+  entry_block->AddInstruction(new (&allocator_) HGoto());
+  block->AddInstruction(new (&allocator_) HReturn(zero));
+  exit_block->AddInstruction(new (&allocator_) HExit());
+
+  const std::string expected_before =
+      "BasicBlock 0, succ: 1\n"
+      "  0: ParameterValue [16, 14, 12, 10, 8, 6, 4, 2]\n"
+      "  1: IntConstant [19, 16, 14, 12, 10, 8, 6, 4, 2]\n"
+      "  18: Goto 1\n"
+      "BasicBlock 1, pred: 0, succ: 2\n"
+      "  2: Above(1, 0) [3]\n"
+      "  3: Deoptimize(2)\n"
+      "  4: Above(0, 1) [5]\n"
+      "  5: Deoptimize(4)\n"
+      "  6: AboveOrEqual(1, 0) [7]\n"
+      "  7: Deoptimize(6)\n"
+      "  8: AboveOrEqual(0, 1) [9]\n"
+      "  9: Deoptimize(8)\n"
+      "  10: Below(1, 0) [11]\n"
+      "  11: Deoptimize(10)\n"
+      "  12: Below(0, 1) [13]\n"
+      "  13: Deoptimize(12)\n"
+      "  14: BelowOrEqual(1, 0) [15]\n"
+      "  15: Deoptimize(14)\n"
+      "  16: BelowOrEqual(0, 1) [17]\n"
+      "  17: Deoptimize(16)\n"
+      "  19: Return(1)\n"
+      "BasicBlock 2, pred: 1\n"
+      "  20: Exit\n";
+
+  const std::string expected_after_cf =
+      "BasicBlock 0, succ: 1\n"
+      "  0: ParameterValue [16, 10, 6, 4]\n"
+      "  1: IntConstant [13, 3, 19, 16, 10, 6, 4]\n"
+      "  21: IntConstant [15, 9]\n"
+      "  18: Goto 1\n"
+      "BasicBlock 1, pred: 0, succ: 2\n"
+      "  3: Deoptimize(1)\n"
+      "  4: Above(0, 1) [5]\n"
+      "  5: Deoptimize(4)\n"
+      "  6: AboveOrEqual(1, 0) [7]\n"
+      "  7: Deoptimize(6)\n"
+      "  9: Deoptimize(21)\n"
+      "  10: Below(1, 0) [11]\n"
+      "  11: Deoptimize(10)\n"
+      "  13: Deoptimize(1)\n"
+      "  15: Deoptimize(21)\n"
+      "  16: BelowOrEqual(0, 1) [17]\n"
+      "  17: Deoptimize(16)\n"
+      "  19: Return(1)\n"
+      "BasicBlock 2, pred: 1\n"
+      "  20: Exit\n";
+
+  const std::string expected_after_dce = expected_after_cf;
+
+  auto check_after_cf = [](HGraph* graph) {
+    CHECK(graph != nullptr);
+  };
+
+  TestCodeOnReadyGraph(expected_before,
+                       expected_after_cf,
+                       expected_after_dce,
+                       check_after_cf);
+}
+
 }  // namespace art