[turbofan] Strength reduction for inline comparisons.

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/diamond.h"
@@ skipping 142 matching lines @@
     case IrOpcode::kWord32Shl:
       return ReduceWord32Shl(node);
     case IrOpcode::kWord32Shr: {
       Uint32BinopMatcher m(node);
       if (m.right().Is(0)) return Replace(m.left().node());  // x >>> 0 => x
       if (m.IsFoldable()) {                                  // K >>> K => K
         return ReplaceInt32(m.left().Value() >> m.right().Value());
       }
       return ReduceWord32Shifts(node);
     }
-    case IrOpcode::kWord32Sar: {
-      Int32BinopMatcher m(node);
-      if (m.right().Is(0)) return Replace(m.left().node());  // x >> 0 => x
-      if (m.IsFoldable()) {                                  // K >> K => K
-        return ReplaceInt32(m.left().Value() >> m.right().Value());
-      }
-      if (m.left().IsWord32Shl()) {
-        Int32BinopMatcher mleft(m.left().node());
-        if (mleft.left().IsLoad()) {
-          LoadRepresentation const rep =
-              OpParameter<LoadRepresentation>(mleft.left().node());
-          if (m.right().Is(24) && mleft.right().Is(24) && rep == kMachInt8) {
-            // Load[kMachInt8] << 24 >> 24 => Load[kMachInt8]
-            return Replace(mleft.left().node());
-          }
-          if (m.right().Is(16) && mleft.right().Is(16) && rep == kMachInt16) {
-            // Load[kMachInt16] << 16 >> 16 => Load[kMachInt8]
-            return Replace(mleft.left().node());
-          }
-        }
-      }
-      return ReduceWord32Shifts(node);
-    }
+    case IrOpcode::kWord32Sar:
+      return ReduceWord32Sar(node);
     case IrOpcode::kWord32Ror: {
       Int32BinopMatcher m(node);
       if (m.right().Is(0)) return Replace(m.left().node());  // x ror 0 => x
       if (m.IsFoldable()) {                                  // K ror K => K
         return ReplaceInt32(
             base::bits::RotateRight32(m.left().Value(), m.right().Value()));
       }
       break;
     }
     case IrOpcode::kWord32Equal: {
@@ skipping 268 matching lines @@
 
 
 Reduction MachineOperatorReducer::ReduceInt32Add(Node* node) {
   DCHECK_EQ(IrOpcode::kInt32Add, node->opcode());
   Int32BinopMatcher m(node);
   if (m.right().Is(0)) return Replace(m.left().node());  // x + 0 => x
   if (m.IsFoldable()) {                                  // K + K => K
     return ReplaceUint32(bit_cast<uint32_t>(m.left().Value()) +
                          bit_cast<uint32_t>(m.right().Value()));
   }
+  if (m.left().IsInt32Sub()) {
+    Int32BinopMatcher mleft(m.left().node());
+    if (mleft.left().Is(0)) {  // (0 - x) + y => y - x
+      node->set_op(machine()->Int32Sub());
+      node->ReplaceInput(0, m.right().node());
+      node->ReplaceInput(1, mleft.right().node());
+      Reduction const reduction = ReduceInt32Sub(node);
+      return reduction.Changed() ? reduction : Changed(node);
+    }
+  }
+  if (m.right().IsInt32Sub()) {
+    Int32BinopMatcher mright(m.right().node());
+    if (mright.left().Is(0)) {  // y + (0 - x) => y - x
+      node->set_op(machine()->Int32Sub());
+      node->ReplaceInput(1, mright.right().node());
+      Reduction const reduction = ReduceInt32Sub(node);
+      return reduction.Changed() ? reduction : Changed(node);
+    }
+  }
   return NoChange();
 }
 
 
 Reduction MachineOperatorReducer::ReduceInt32Sub(Node* node) {
   DCHECK_EQ(IrOpcode::kInt32Sub, node->opcode());
   Int32BinopMatcher m(node);
   if (m.right().Is(0)) return Replace(m.left().node());  // x - 0 => x
   if (m.IsFoldable()) {                                  // K - K => K
     return ReplaceInt32(static_cast<uint32_t>(m.left().Value()) -
@@ skipping 293 matching lines @@
                            Uint32Constant(~((1U << m.right().Value()) - 1U)));
         Reduction reduction = ReduceWord32And(node);
         return reduction.Changed() ? reduction : Changed(node);
       }
     }
   }
   return ReduceWord32Shifts(node);
 }
 
 
+Reduction MachineOperatorReducer::ReduceWord32Sar(Node* node) {
+  Int32BinopMatcher m(node);
+  if (m.right().Is(0)) return Replace(m.left().node());  // x >> 0 => x
+  if (m.IsFoldable()) {                                  // K >> K => K
+    return ReplaceInt32(m.left().Value() >> m.right().Value());
+  }
+  if (m.left().IsWord32Shl()) {
+    Int32BinopMatcher mleft(m.left().node());
+    if (mleft.left().IsComparison()) {
+      if (m.right().Is(31) && mleft.right().Is(31)) {
+        // Comparison << 31 >> 31 => 0 - Comparison
+        node->set_op(machine()->Int32Sub());
+        node->ReplaceInput(0, Int32Constant(0));
+        node->ReplaceInput(1, mleft.left().node());
+        Reduction const reduction = ReduceInt32Sub(node);
+        return reduction.Changed() ? reduction : Changed(node);
+      }
+    } else if (mleft.left().IsLoad()) {
+      LoadRepresentation const rep =
+          OpParameter<LoadRepresentation>(mleft.left().node());
+      if (m.right().Is(24) && mleft.right().Is(24) && rep == kMachInt8) {
+        // Load[kMachInt8] << 24 >> 24 => Load[kMachInt8]
+        return Replace(mleft.left().node());
+      }
+      if (m.right().Is(16) && mleft.right().Is(16) && rep == kMachInt16) {
+        // Load[kMachInt16] << 16 >> 16 => Load[kMachInt8]
+        return Replace(mleft.left().node());
+      }
+    }
+  }
+  return ReduceWord32Shifts(node);
+}
+
+
 Reduction MachineOperatorReducer::ReduceWord32And(Node* node) {
   DCHECK_EQ(IrOpcode::kWord32And, node->opcode());
   Int32BinopMatcher m(node);
   if (m.right().Is(0)) return Replace(m.right().node());  // x & 0  => 0
   if (m.right().Is(-1)) return Replace(m.left().node());  // x & -1 => x
+  if (m.left().IsComparison() && m.right().Is(1)) {       // CMP & 1 => CMP
+    return Replace(m.left().node());
+  }
   if (m.IsFoldable()) {                                   // K & K  => K
     return ReplaceInt32(m.left().Value() & m.right().Value());
   }
   if (m.LeftEqualsRight()) return Replace(m.left().node());  // x & x => x
   if (m.left().IsWord32And() && m.right().HasValue()) {
     Int32BinopMatcher mleft(m.left().node());
     if (mleft.right().HasValue()) {  // (x & K) & K => x & K
       node->ReplaceInput(0, mleft.left().node());
       node->ReplaceInput(
           1, Int32Constant(m.right().Value() & mleft.right().Value()));
@@ skipping 140 matching lines @@
 MachineOperatorBuilder* MachineOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
 
 Graph* MachineOperatorReducer::graph() const { return jsgraph()->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8