[turbofan] Introduce new Select operator to improve bounds checking.

src/compiler/control-reducer.cc

Index: src/compiler/control-reducer.cc
diff --git a/src/compiler/control-reducer.cc b/src/compiler/control-reducer.cc
index 533fb23997614e8c2503a2f1959c77d4424257a5..b06076457e5e5ae723655486a1fde289dc0e3147 100644
--- a/src/compiler/control-reducer.cc
+++ b/src/compiler/control-reducer.cc
@@ -322,6 +322,8 @@ class ControlReducerImpl {
       case IrOpcode::kLoop:
       case IrOpcode::kMerge:
         return ReduceMerge(node);
+      case IrOpcode::kSelect:
+        return ReduceSelect(node);
       case IrOpcode::kPhi:
       case IrOpcode::kEffectPhi:
         return ReducePhi(node);
@@ -330,6 +332,32 @@ class ControlReducerImpl {
     }
   }
 
+  // Reduce redundant selects.
+  Node* ReduceSelect(Node* const node) {
+    Node* const cond = node->InputAt(0);
+    Node* const tvalue = node->InputAt(1);
+    Node* const fvalue = node->InputAt(2);
+    if (tvalue == fvalue) return tvalue;
+    switch (cond->opcode()) {
+      case IrOpcode::kInt32Constant:
+        return Int32Matcher(cond).Is(0) ? fvalue : tvalue;
+      case IrOpcode::kInt64Constant:
+        return Int64Matcher(cond).Is(0) ? fvalue : tvalue;
+      case IrOpcode::kNumberConstant:
+        return NumberMatcher(cond).Is(0) ? fvalue : tvalue;
+      case IrOpcode::kHeapConstant: {
+        Handle<Object> object =
+            HeapObjectMatcher<Object>(cond).Value().handle();
+        if (object->IsTrue()) return tvalue;
+        if (object->IsFalse()) return fvalue;
+        break;
+      }
+      default:
+        break;
+    }
+    return node;
+  }
+
   // Reduce redundant phis.
   Node* ReducePhi(Node* node) {
     int n = node->InputCount();
@@ -406,6 +434,9 @@ class ControlReducerImpl {
       case IrOpcode::kInt32Constant:
         is_true = !Int32Matcher(cond).Is(0);
         break;
+      case IrOpcode::kInt64Constant:
+        is_true = !Int64Matcher(cond).Is(0);
+        break;
       case IrOpcode::kNumberConstant:
         is_true = !NumberMatcher(cond).Is(0);
         break;