[turbofan] Strip useless sign-extension for store8/store16.

src/compiler/machine-operator-reducer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/machine-operator-reducer.h"
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/codegen.h"
 #include "src/compiler/generic-node-inl.h"
@@ skipping 516 matching lines @@
       if (m.HasValue()) return ReplaceInt32(static_cast<int32_t>(m.Value()));
       if (m.IsChangeInt32ToInt64()) return Replace(m.node()->InputAt(0));
       break;
     }
     case IrOpcode::kTruncateFloat64ToFloat32: {
       Float64Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceFloat32(DoubleToFloat32(m.Value()));
       if (m.IsChangeFloat32ToFloat64()) return Replace(m.node()->InputAt(0));
       break;
     }
-    case IrOpcode::kStore: {
-      Node* const value = node->InputAt(2);
-      // TODO(turbofan): Extend to 64-bit?
-      if (value->opcode() == IrOpcode::kWord32And) {
-        MachineType const rep = static_cast<MachineType>(
-            StoreRepresentationOf(node->op()).machine_type() & kRepMask);
-        Uint32BinopMatcher m(value);
-        if (m.right().HasValue() &&
-            ((rep == kRepWord8 && (m.right().Value() & 0xff) == 0xff) ||
-             (rep == kRepWord16 && (m.right().Value() & 0xffff) == 0xffff))) {
-          node->ReplaceInput(2, m.left().node());
-          return Changed(node);
-        }
-      }
-      break;
-    }
+    case IrOpcode::kStore:
+      return ReduceStore(node);
     default:
       break;
   }
   return NoChange();
 }
 
 
 Reduction MachineOperatorReducer::ReduceInt32Div(Node* node) {
   Int32BinopMatcher m(node);
   if (m.left().Is(0)) return Replace(m.left().node());    // 0 / x => 0
@@ skipping 142 matching lines @@
       DCHECK_EQ(dividend, node->InputAt(0));
       node->ReplaceInput(1, Int32Mul(quotient, Uint32Constant(divisor)));
     }
     node->TrimInputCount(2);
     return Changed(node);
   }
   return NoChange();
 }
 
 
+Reduction MachineOperatorReducer::ReduceStore(Node* node) {
+  MachineType const rep =
+      RepresentationOf(StoreRepresentationOf(node->op()).machine_type());
+  Node* const value = node->InputAt(2);
+  switch (value->opcode()) {
+    case IrOpcode::kWord32And: {
+      Uint32BinopMatcher m(value);
+      if (m.right().HasValue() &&
+          ((rep == kRepWord8 && (m.right().Value() & 0xff) == 0xff) ||
+           (rep == kRepWord16 && (m.right().Value() & 0xffff) == 0xffff))) {
+        node->ReplaceInput(2, m.left().node());
+        return Changed(node);
+      }
+      break;
+    }
+    case IrOpcode::kWord32Sar: {
+      Int32BinopMatcher m(value);
+      if (m.left().IsWord32Shl() &&
+          ((rep == kRepWord8 && m.right().IsInRange(1, 24)) ||
+           (rep == kRepWord16 && m.right().IsInRange(1, 16)))) {
+        Int32BinopMatcher mleft(m.left().node());
+        if (mleft.right().Is(m.right().Value())) {
+          node->ReplaceInput(2, mleft.left().node());
+          return Changed(node);
+        }
+      }
+      break;
+    }
+    default:
+      break;
+  }
+  return NoChange();
+}
+
+
 Reduction MachineOperatorReducer::ReduceProjection(size_t index, Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kInt32AddWithOverflow: {
       DCHECK(index == 0 || index == 1);
       Int32BinopMatcher m(node);
       if (m.IsFoldable()) {
         int32_t val;
         bool ovf = base::bits::SignedAddOverflow32(m.left().Value(),
                                                    m.right().Value(), &val);
         return ReplaceInt32((index == 0) ? val : ovf);
@@ skipping 32 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8