[stubs] Don't unconditionally canonicalize in ChangeFloat64ToTagged.

Add a CanonicalizationMode to CodeStubAssembler::ChangeFloat64ToTagged,
so clients can request Smi canonicalization when desired, but otherwise
get Crankshaft/Fullcodegen compatible behavior of just boxing the double
into a HeapNumber.

R=verwaest@chromium.org
BUG=v8:5268

Review-Url: https://codereview.chromium.org/2380543002
Cr-Commit-Position: refs/heads/master@{#39804}

src/code-stub-assembler.cc

@@ -1870,53 +1870,64 @@ Node* CodeStubAssembler::TruncateHeapNumberValueToWord32(Node* object) {
   return TruncateFloat64ToWord32(value);
 }
 
-Node* CodeStubAssembler::ChangeFloat64ToTagged(Node* value) {
-  Node* value32 = RoundFloat64ToInt32(value);
-  Node* value64 = ChangeInt32ToFloat64(value32);
-
-  Label if_valueisint32(this), if_valueisheapnumber(this), if_join(this);
+Node* CodeStubAssembler::ChangeFloat64ToTagged(Node* value,
+                                               CanonicalizationMode mode) {
+  switch (mode) {
+    case CanonicalizationMode::kDontCanonicalize: {
+      return AllocateHeapNumberWithValue(value);
+    }
+    case CanonicalizationMode::kCanonicalize: {
+      Node* value32 = RoundFloat64ToInt32(value);
+      Node* value64 = ChangeInt32ToFloat64(value32);
 
-  Label if_valueisequal(this), if_valueisnotequal(this);
-  Branch(Float64Equal(value, value64), &if_valueisequal, &if_valueisnotequal);
-  Bind(&if_valueisequal);
-  {
-    GotoUnless(Word32Equal(value32, Int32Constant(0)), &if_valueisint32);
-    BranchIfInt32LessThan(Float64ExtractHighWord32(value), Int32Constant(0),
-                          &if_valueisheapnumber, &if_valueisint32);
-  }
-  Bind(&if_valueisnotequal);
-  Goto(&if_valueisheapnumber);
+      Label if_valueisint32(this), if_valueisheapnumber(this), if_join(this);
 
-  Variable var_result(this, MachineRepresentation::kTagged);
-  Bind(&if_valueisint32);
-  {
-    if (Is64()) {
-      Node* result = SmiTag(ChangeInt32ToInt64(value32));
-      var_result.Bind(result);
-      Goto(&if_join);
-    } else {
-      Node* pair = Int32AddWithOverflow(value32, value32);
-      Node* overflow = Projection(1, pair);
-      Label if_overflow(this, Label::kDeferred), if_notoverflow(this);
-      Branch(overflow, &if_overflow, &if_notoverflow);
-      Bind(&if_overflow);
+      Label if_valueisequal(this), if_valueisnotequal(this);
+      Branch(Float64Equal(value, value64), &if_valueisequal,
+             &if_valueisnotequal);
+      Bind(&if_valueisequal);
+      {
+        GotoUnless(Word32Equal(value32, Int32Constant(0)), &if_valueisint32);
+        BranchIfInt32LessThan(Float64ExtractHighWord32(value), Int32Constant(0),
+                              &if_valueisheapnumber, &if_valueisint32);
+      }
+      Bind(&if_valueisnotequal);
       Goto(&if_valueisheapnumber);
-      Bind(&if_notoverflow);
+
+      Variable var_result(this, MachineRepresentation::kTagged);
+      Bind(&if_valueisint32);
+      {
+        if (Is64()) {
+          Node* result = SmiTag(ChangeInt32ToInt64(value32));
+          var_result.Bind(result);
+          Goto(&if_join);
+        } else {
+          Node* pair = Int32AddWithOverflow(value32, value32);
+          Node* overflow = Projection(1, pair);
+          Label if_overflow(this, Label::kDeferred), if_notoverflow(this);
+          Branch(overflow, &if_overflow, &if_notoverflow);
+          Bind(&if_overflow);
+          Goto(&if_valueisheapnumber);
+          Bind(&if_notoverflow);
+          {
+            Node* result = Projection(0, pair);
+            var_result.Bind(result);
+            Goto(&if_join);
+          }
+        }
+      }
+      Bind(&if_valueisheapnumber);
       {
-        Node* result = Projection(0, pair);
+        Node* result = AllocateHeapNumberWithValue(value);
         var_result.Bind(result);
         Goto(&if_join);
       }
+      Bind(&if_join);
+      return var_result.value();
     }
   }
-  Bind(&if_valueisheapnumber);
-  {
-    Node* result = AllocateHeapNumberWithValue(value);
-    var_result.Bind(result);
-    Goto(&if_join);
-  }
-  Bind(&if_join);
-  return var_result.value();
+  UNREACHABLE();
+  return nullptr;
 }
 
 Node* CodeStubAssembler::ChangeInt32ToTagged(Node* value) {
@@ -2632,12 +2643,21 @@ Node* CodeStubAssembler::ToInteger(Node* context, Node* input,
       // Truncate {arg} towards zero.
       Node* value = Float64Trunc(arg_value);
 
-      if (mode == kTruncateMinusZero) {
-        // Truncate -0.0 to 0.
-        GotoIf(Float64Equal(value, Float64Constant(0.0)), &return_zero);
+      // Perform optional minus zero truncation.
+      switch (mode) {
+        case kNoTruncation:
+          break;
+        case kTruncateMinusZero: {
+          // Truncate -0.0 to 0.
+          GotoIf(Float64Equal(value, Float64Constant(0.0)), &return_zero);
+          break;
+        }
       }
 
-      var_arg.Bind(ChangeFloat64ToTagged(value));
+      // Tag the {value} using Smi canonicalization, i.e. if {value} can be
+      // represented as a Smi, then this will produce a Smi.
+      var_arg.Bind(
+          ChangeFloat64ToTagged(value, CanonicalizationMode::kCanonicalize));
       Goto(&out);
     }
 

src/code-stub-assembler.h

@@ -17,6 +17,7 @@ class CallInterfaceDescriptor;
 class StatsCounter;
 class StubCache;
 
+enum class CanonicalizationMode { kDontCanonicalize, kCanonicalize };
 enum class PrimitiveType { kBoolean, kNumber, kString, kSymbol };
 
 enum class UnicodeEncoding {
@@ -427,7 +428,11 @@ class CodeStubAssembler : public compiler::CodeAssembler {
   compiler::Node* TruncateHeapNumberValueToWord32(compiler::Node* object);
 
   // Conversions.
-  compiler::Node* ChangeFloat64ToTagged(compiler::Node* value);
+  // Returns a tagged representation of the float64 {value}. Might optionally
+  // try to canonicalize to Smi representation if the {value} is in Smi range.
+  compiler::Node* ChangeFloat64ToTagged(
+      compiler::Node* value,
+      CanonicalizationMode mode = CanonicalizationMode::kDontCanonicalize);
   compiler::Node* ChangeInt32ToTagged(compiler::Node* value);
   compiler::Node* ChangeUint32ToTagged(compiler::Node* value);