[turbofan] fold constants in compares

test/unittests/compiler/machine-operator-reducer-unittest.cc

Index: test/unittests/compiler/machine-operator-reducer-unittest.cc
diff --git a/test/unittests/compiler/machine-operator-reducer-unittest.cc b/test/unittests/compiler/machine-operator-reducer-unittest.cc
index fff6f96709d072ecf055c927800d2532a73280c3..33c5489a6f5f9a62bfe32981b9100f0ff4aa71c2 100644
--- a/test/unittests/compiler/machine-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/machine-operator-reducer-unittest.cc
@@ -232,6 +232,12 @@ const uint32_t kUint32Values[] = {
     0x000fffff, 0x0007ffff, 0x0003ffff, 0x0001ffff, 0x0000ffff, 0x00007fff,
     0x00003fff, 0x00001fff, 0x00000fff, 0x000007ff, 0x000003ff, 0x000001ff};
 
+
+int32_t RandomInt32(base::RandomNumberGenerator* rng) {
+  int index = rng->NextInt(static_cast<int>(arraysize(kInt32Values)));
+  return kInt32Values[index];
+}
+
 }  // namespace
 
 
@@ -1144,6 +1150,43 @@ TEST_F(MachineOperatorReducerTest, StoreRepWord16WithWord32And) {
   }
 }
 
+
+TEST_F(MachineOperatorReducerTest, ConstantFoldCompare32) {
+  base::RandomNumberGenerator rng;
+  TRACED_FOREACH(int32_t, c_0, kInt32Values) {
+    const int32_t c_1 = RandomInt32(&rng);
+    const int32_t c_2 = RandomInt32(&rng);
+    {
+      Node* const k_0 = Int32Constant(c_0);
+      Node* const k_1 = Int32Constant(c_1);
+      Node* const k_2 = Int32Constant(c_2);
+      Node* const p0 = Parameter(0);
+      Node* const add_0 = graph()->NewNode(machine()->Int32Add(), p0, k_0);
+      Node* const add_1 = graph()->NewNode(machine()->Int32Add(), add_0, k_1);
+      Node* const node =
+          graph()->NewNode(machine()->Int32LessThan(), add_1, k_2);
+      Reduction r = Reduce(node);
+      ASSERT_TRUE(r.Changed());
+      EXPECT_THAT(r.replacement(),
+                  IsInt32LessThan(p0, IsInt32Constant(c_2 - c_1 - c_0)));
+    }
+    {
+      Node* const k_0 = Int32Constant(c_0);
+      Node* const k_1 = Int32Constant(c_1);
+      Node* const k_2 = Int32Constant(c_2);
+      Node* const p0 = Parameter(0);
+      Node* const add_0 = graph()->NewNode(machine()->Int32Add(), p0, k_0);
+      Node* const add_1 = graph()->NewNode(machine()->Int32Add(), add_0, k_1);
+      Node* const node =
+          graph()->NewNode(machine()->Int32LessThan(), k_2, add_1);
+      Reduction r = Reduce(node);
+      ASSERT_TRUE(r.Changed());
+      EXPECT_THAT(r.replacement(),
+                  IsInt32LessThan(IsInt32Constant(c_2 - c_1 - c_0), p0));
+    }
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8