[turbofan] Optimize Int32Mod by power-of-two.

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 6c46a5bd95874848eedc5a327756170c08b2fba6..9ee74cee0990d2fdab59d4fe3952b6a36bf62c5b 100644
--- a/test/unittests/compiler/machine-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/machine-operator-reducer-unittest.cc
@@ -7,6 +7,11 @@
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/compiler/typer.h"
 #include "test/unittests/compiler/graph-unittest.h"
+#include "testing/gmock-support.h"
+
+using testing::AllOf;
+using testing::Capture;
+using testing::CaptureEq;
 
 namespace v8 {
 namespace internal {
@@ -564,6 +569,37 @@ TEST_F(MachineOperatorReducerTest, Word32ShlWithWord32Shr) {
 
 
 // -----------------------------------------------------------------------------
+// Int32Mod
+
+
+TEST_F(MachineOperatorReducerTest, Int32ModWithPowerOfTwo) {
+  Node* p0 = Parameter(0);
+  TRACED_FORRANGE(int32_t, x, 1, 30) {
+    int32_t const divisor = 1 << x;
+    Node* node =
+        graph()->NewNode(machine()->Int32Mod(), p0, Int32Constant(divisor));
+    Reduction r = Reduce(node);
+    ASSERT_TRUE(r.Changed());
+
+    Capture<Node*> branch;
+    Node* phi = r.replacement();
+    int32_t const mask = divisor - 1;
+    EXPECT_THAT(
+        phi, IsPhi(kMachInt32,
+                   IsInt32Sub(IsInt32Constant(0),
+                              IsWord32And(IsInt32Sub(IsInt32Constant(0), p0),
+                                          IsInt32Constant(mask))),
+                   IsWord32And(p0, IsInt32Constant(mask)),
+                   IsMerge(IsIfTrue(CaptureEq(&branch)),
+                           IsIfFalse(AllOf(
+                               CaptureEq(&branch),
+                               IsBranch(IsInt32LessThan(p0, IsInt32Constant(0)),
+                                        graph()->start()))))));
+  }
+}
+
+
+// -----------------------------------------------------------------------------
 // Int32AddWithOverflow