[Interpreter] Introduce IncStub and DecStub.

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 84d8d98c8eace1582719037fc752c9338b2dd7e6..3d5c0eb7b86ce18c7103572ca1d98dd1f8310315 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -1608,6 +1608,160 @@ void BitwiseXorStub::GenerateAssembly(CodeStubAssembler* assembler) const {
   assembler->Return(result);
 }
 
+void IncStub::GenerateAssembly(CodeStubAssembler* assembler) const {
+  typedef CodeStubAssembler::Label Label;
+  typedef compiler::Node Node;
+  typedef CodeStubAssembler::Variable Variable;
+
+  Node* value = assembler->Parameter(0);
+  Node* context = assembler->Parameter(1);
+
+  // Shared entry for floating point increment.
+  Label do_finc(assembler);
+  Variable var_finc_value(assembler, MachineRepresentation::kFloat64);
+
+  // Input has been converted to a number using ToNumber, so it must be a

[epertoso, 2016/04/19 15:48:23]

Where does this conversion happen?

[rmcilroy, 2016/04/19 15:50:03]

In BytecodeGenerator::VisitCountOperation. The value always goes via the
CastAccumulatorToNumber bytecode before it is an input to CountOperation.

+  // Smi or a HeapNumber.
+  Label if_issmi(assembler), if_isnotsmi(assembler);
+  assembler->Branch(assembler->WordIsSmi(value), &if_issmi, &if_isnotsmi);
+
+  assembler->Bind(&if_issmi);
+  {
+    // Try fast Smi addition first.
+    Node* one = assembler->SmiConstant(Smi::FromInt(1));
+    Node* pair = assembler->SmiAddWithOverflow(value, one);
+    Node* overflow = assembler->Projection(1, pair);
+
+    // Check if the Smi additon overflowed.
+    Label if_overflow(assembler), if_notoverflow(assembler);
+    assembler->Branch(overflow, &if_overflow, &if_notoverflow);
+
+    assembler->Bind(&if_notoverflow);
+    assembler->Return(assembler->Projection(0, pair));
+
+    assembler->Bind(&if_overflow);
+    {
+      var_finc_value.Bind(assembler->SmiToFloat64(value));
+      assembler->Goto(&do_finc);
+    }
+  }
+
+  assembler->Bind(&if_isnotsmi);
+  {
+    // Value must be a heap number if we reach this point.
+    if (FLAG_debug_code) {
+      // Assert that the value is a HeapNumber.
+      Node* value_map = assembler->LoadMap(value);
+
+      Label if_valueisnumber(assembler),
+          if_valuenotnumber(assembler, Label::kDeferred);
+      Node* number_map = assembler->HeapNumberMapConstant();
+      assembler->Branch(assembler->WordEqual(value_map, number_map),
+                        &if_valueisnumber, &if_valuenotnumber);
+
+      assembler->Bind(&if_valuenotnumber);
+      {
+        Node* abort_id = assembler->SmiConstant(
+            Smi::FromInt(BailoutReason::kExpectedHeapNumber));
+        assembler->CallRuntime(Runtime::kAbort, context, abort_id);
+        assembler->Goto(&if_valueisnumber);  // Won't actually be reached.
+      }
+
+      assembler->Bind(&if_valueisnumber);
+    }
+
+    // Load the heap number value
+    var_finc_value.Bind(assembler->LoadHeapNumberValue(value));
+    assembler->Goto(&do_finc);
+  }
+
+  assembler->Bind(&do_finc);
+  {
+    Node* finc_value = var_finc_value.value();
+    Node* one = assembler->Float64Constant(1.0);
+    Node* finc_result = assembler->Float64Add(finc_value, one);
+    Node* result = assembler->ChangeFloat64ToTagged(finc_result);
+    assembler->Return(result);
+  }
+}
+
+void DecStub::GenerateAssembly(CodeStubAssembler* assembler) const {
+  typedef CodeStubAssembler::Label Label;
+  typedef compiler::Node Node;
+  typedef CodeStubAssembler::Variable Variable;
+
+  Node* value = assembler->Parameter(0);
+  Node* context = assembler->Parameter(1);
+
+  // Shared entry for floating point increment.
+  Label do_fdec(assembler);
+  Variable var_fdec_value(assembler, MachineRepresentation::kFloat64);
+
+  // Input has been converted to a number using ToNumber, so it must be a
+  // Smi or a HeapNumber.
+  Label if_issmi(assembler), if_isnotsmi(assembler);
+  assembler->Branch(assembler->WordIsSmi(value), &if_issmi, &if_isnotsmi);
+
+  assembler->Bind(&if_issmi);
+  {
+    // Try fast Smi addition first.
+    Node* one = assembler->SmiConstant(Smi::FromInt(1));
+    Node* pair = assembler->SmiSubWithOverflow(value, one);
+    Node* overflow = assembler->Projection(1, pair);
+
+    // Check if the Smi subtraction overflowed.
+    Label if_overflow(assembler), if_notoverflow(assembler);
+    assembler->Branch(overflow, &if_overflow, &if_notoverflow);
+
+    assembler->Bind(&if_notoverflow);
+    assembler->Return(assembler->Projection(0, pair));
+
+    assembler->Bind(&if_overflow);
+    {
+      var_fdec_value.Bind(assembler->SmiToFloat64(value));
+      assembler->Goto(&do_fdec);
+    }
+  }
+
+  assembler->Bind(&if_isnotsmi);
+  {
+    // Value must be a heap number if we reach this point.
+    if (FLAG_debug_code) {
+      // Assert that the value is a HeapNumber.
+      Node* value_map = assembler->LoadMap(value);
+
+      Label if_valueisnumber(assembler),
+          if_valuenotnumber(assembler, Label::kDeferred);
+      Node* number_map = assembler->HeapNumberMapConstant();
+      assembler->Branch(assembler->WordEqual(value_map, number_map),
+                        &if_valueisnumber, &if_valuenotnumber);
+
+      assembler->Bind(&if_valuenotnumber);
+      {
+        Node* abort_id = assembler->SmiConstant(
+            Smi::FromInt(BailoutReason::kExpectedHeapNumber));
+        assembler->CallRuntime(Runtime::kAbort, context, abort_id);
+        assembler->Goto(&if_valueisnumber);  // Won't actually be reached.
+      }
+
+      assembler->Bind(&if_valueisnumber);
+    }
+
+    // Load the heap number value
+    var_fdec_value.Bind(assembler->LoadHeapNumberValue(value));
+    assembler->Goto(&do_fdec);
+  }
+
+  assembler->Bind(&do_fdec);
+  {
+    Node* fdec_value = var_fdec_value.value();
+    Node* one = assembler->Float64Constant(1.0);
+    Node* fdec_result = assembler->Float64Sub(fdec_value, one);
+    Node* result = assembler->ChangeFloat64ToTagged(fdec_result);
+    assembler->Return(result);
+  }
+}
+
 namespace {
 
 enum RelationalComparisonMode {