[turbofan] Avoid unnecessary (u)int32<->float64 changes in simplified lowering.

src/compiler/simplified-lowering.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/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 290 matching lines @@
 
   // Helper for handling phis.
   void VisitPhi(Node* node, MachineTypeUnion use,
                 SimplifiedLowering* lowering) {
     // Phis adapt to the output representation their uses demand, pushing
     // representation changes to their inputs.
     Type* upper = NodeProperties::GetBounds(node).upper;
     MachineType output = kMachNone;
     MachineType propagate = kMachNone;
 
-    if (upper->Is(Type::Signed32()) || upper->Is(Type::Unsigned32())) {
-      // legal = kRepTagged | kRepFloat64 | kRepWord32;
-      if ((use & kRepMask) == kRepTagged) {
-        // only tagged uses.
-        output = kRepTagged;
-        propagate = kRepTagged;
-      } else if ((use & kRepMask) == kRepFloat64) {
+    if ((use & kRepMask) == kRepTagged) {
+      // only tagged uses.
+      output = kRepTagged;
+      propagate = kRepTagged;
+    } else if (IsSafeIntAdditiveOperand(node)) {
+      // Integer within [-2^52, 2^52] range.
+      if ((use & kRepMask) == kRepFloat64) {
         // only float64 uses.
         output = kRepFloat64;
         propagate = kRepFloat64;
-      } else {
-        // multiple uses.
+      } else if (upper->Is(Type::Signed32()) || upper->Is(Type::Unsigned32())) {
+        // multiple uses, but we are within 32 bits range => pick kRepWord32.
         output = kRepWord32;
         propagate = kRepWord32;
-      }
-    } else if (upper->Is(Type::Boolean())) {
-      // legal = kRepTagged | kRepBit;
-      if ((use & kRepMask) == kRepTagged) {
-        // only tagged uses.
-        output = kRepTagged;
-        propagate = kRepTagged;
+      } else if ((use & kRepMask) == kRepWord32 ||
+                 (use & kTypeMask) == kTypeInt32 ||
+                 (use & kTypeMask) == kTypeUint32) {
+        // The type is a safe integer, but we only use 32 bits.
+        output = kRepWord32;
+        propagate = kRepWord32;
       } else {
-        // multiple uses.
-        output = kRepBit;
-        propagate = kRepBit;
-      }
-    } else if (upper->Is(Type::Number())) {
-      // legal = kRepTagged | kRepFloat64;
-      if ((use & kRepMask) == kRepTagged) {
-        // only tagged uses.
-        output = kRepTagged;
-        propagate = kRepTagged;
-      } else {
-        // multiple uses.
         output = kRepFloat64;
         propagate = kRepFloat64;
       }
+    } else if (upper->Is(Type::Boolean())) {
+      // multiple uses => pick kRepBit.
+      output = kRepBit;
+      propagate = kRepBit;
+    } else if (upper->Is(Type::Number())) {
+      // multiple uses => pick kRepFloat64.
+      output = kRepFloat64;
+      propagate = kRepFloat64;
     } else {
       // legal = kRepTagged;
       output = kRepTagged;
       propagate = kRepTagged;
     }
 
     MachineType output_type =
         static_cast<MachineType>(changer_->TypeFromUpperBound(upper) | output);
     SetOutput(node, output_type);
 
@@ skipping 283 matching lines @@
           }
         }
         // => Float64Mod
         VisitFloat64Binop(node);
         if (lower()) node->set_op(Float64Op(node));
         break;
       }
       case IrOpcode::kNumberToInt32: {
         MachineTypeUnion use_rep = use & kRepMask;
         Node* input = node->InputAt(0);
+        Type* in_upper = NodeProperties::GetBounds(input).upper;
         MachineTypeUnion in = GetInfo(input)->output;
-        if (NodeProperties::GetBounds(input).upper->Is(Type::Signed32())) {
+        if (in_upper->Is(Type::Signed32())) {
           // If the input has type int32, pass through representation.
           VisitUnop(node, kTypeInt32 | use_rep, kTypeInt32 | use_rep);
           if (lower()) DeferReplacement(node, node->InputAt(0));
         } else if ((in & kTypeMask) == kTypeUint32 ||
                    (in & kTypeMask) == kTypeInt32 ||
+                   in_upper->Is(Type::Unsigned32()) ||

[titzer, 2014/10/28 15:10:42]

Something feels a little fishy here. What about making a similar looking case to
the one above like:

if (in_upper->Is(Type::Signed32())) {  // existing
...
} else if (in_upper->Is(Type::Unsigned32())) { // new
...
} else if ((in & kTypeMask) == kTypeUint32) { // existing
...

                    (in & kRepMask) == kRepWord32) {
           // Just change representation if necessary.
           VisitUnop(node, kTypeInt32 | kRepWord32, kTypeInt32 | kRepWord32);
           if (lower()) DeferReplacement(node, node->InputAt(0));
         } else {
           // Require the input in float64 format and perform truncation.
           // TODO(turbofan): avoid a truncation with a smi check.
           VisitUnop(node, kTypeInt32 | kRepFloat64, kTypeInt32 | kRepWord32);
           if (lower())
             node->set_op(lowering->machine()->TruncateFloat64ToInt32());
         }
         break;
       }
       case IrOpcode::kNumberToUint32: {
         MachineTypeUnion use_rep = use & kRepMask;
         Node* input = node->InputAt(0);
+        Type* in_upper = NodeProperties::GetBounds(input).upper;
         MachineTypeUnion in = GetInfo(input)->output;
-        if (NodeProperties::GetBounds(input).upper->Is(Type::Unsigned32())) {
+        if (in_upper->Is(Type::Unsigned32())) {
           // If the input has type uint32, pass through representation.
           VisitUnop(node, kTypeUint32 | use_rep, kTypeUint32 | use_rep);
           if (lower()) DeferReplacement(node, node->InputAt(0));
         } else if ((in & kTypeMask) == kTypeUint32 ||
                    (in & kTypeMask) == kTypeInt32 ||
+                   in_upper->Is(Type::Signed32()) ||
                    (in & kRepMask) == kRepWord32) {
           // Just change representation if necessary.
           VisitUnop(node, kTypeUint32 | kRepWord32, kTypeUint32 | kRepWord32);
           if (lower()) DeferReplacement(node, node->InputAt(0));
         } else {
           // Require the input in float64 format and perform truncation.
           // TODO(turbofan): avoid a truncation with a smi check.
           VisitUnop(node, kTypeUint32 | kRepFloat64, kTypeUint32 | kRepWord32);
           if (lower())
             node->set_op(lowering->machine()->TruncateFloat64ToInt32());
@@ skipping 544 matching lines @@
 void SimplifiedLowering::DoStringLessThanOrEqual(Node* node) {
   node->set_op(machine()->IntLessThanOrEqual());
   node->ReplaceInput(0, StringComparison(node, true));
   node->ReplaceInput(1, jsgraph()->SmiConstant(EQUAL));
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8