[stubs] Introduce LeftShift, SignedRightShift and UnsignedRightShift stubs.

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 1acd977a061a62ea2eedc4406acd0dca647b2605..e8fa554cbbefd397484fd96142faeaf4b91a5cd0 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -1542,6 +1542,76 @@ void ModulusStub::GenerateAssembly(
   }
 }
 
+void LeftShiftStub::GenerateAssembly(
+    compiler::CodeStubAssembler* assembler) const {
+  using compiler::Node;
+
+  Node* lhs = assembler->Parameter(0);
+  Node* rhs = assembler->Parameter(1);
+  Node* context = assembler->Parameter(2);
+  Node* lhs_value = assembler->TruncateTaggedToWord32(context, lhs);
+  Node* rhs_value = assembler->TruncateTaggedToWord32(context, rhs);
+  Node* shift_count =
+      assembler->Word32And(rhs_value, assembler->Int32Constant(0x1f));
+  Node* value = assembler->Word32Shl(lhs_value, shift_count);
+  Node* result = assembler->ChangeInt32ToTagged(value);
+  assembler->Return(result);
+}
+
+void SignedRightShiftStub::GenerateAssembly(
+    compiler::CodeStubAssembler* assembler) const {
+  using compiler::Node;
+
+  Node* lhs = assembler->Parameter(0);
+  Node* rhs = assembler->Parameter(1);
+  Node* context = assembler->Parameter(2);
+  Node* lhs_value = assembler->TruncateTaggedToWord32(context, lhs);
+  Node* rhs_value = assembler->TruncateTaggedToWord32(context, rhs);
+  Node* shift_count =
+      assembler->Word32And(rhs_value, assembler->Int32Constant(0x1f));
+  Node* value = assembler->Word32Sar(lhs_value, shift_count);
+  Node* result = assembler->ChangeInt32ToTagged(value);
+  assembler->Return(result);
+}
+
+void UnsignedRightShiftStub::GenerateAssembly(
+    compiler::CodeStubAssembler* assembler) const {
+  using compiler::Node;
+  typedef compiler::CodeStubAssembler::Label Label;
+
+  Node* lhs = assembler->Parameter(0);
+  Node* rhs = assembler->Parameter(1);
+  Node* context = assembler->Parameter(2);
+  Node* lhs_value = assembler->TruncateTaggedToWord32(context, lhs);
+  Node* rhs_value = assembler->TruncateTaggedToWord32(context, rhs);
+  Node* shift_count =
+      assembler->Word32And(rhs_value, assembler->Int32Constant(0x1f));
+  Node* value = assembler->Word32Shr(lhs_value, shift_count);
+
+  Label if_smi_overflow(assembler, Label::kDeferred),

[Benedikt Meurer, 2016/04/12 12:55:20]

Nit: Can you wrap this into ChangeUint32ToTagged?

[epertoso, 2016/04/12 15:10:16]

Sure.

+      if_not_smi_overflow(assembler);
+  // If the sign bit on {value} is set, we always need a heap number to
+  // represent the unsigned value. This is sufficient for both 32 and 31 bit
+  // Smis, as ChangeInt32ToTagged will allocate a HeapNumber for us when tagging
+  // the Smi causes an 32-bit integer overflow.
+  assembler->Branch(
+      assembler->Int32LessThan(value, assembler->Int32Constant(0)),
+      &if_smi_overflow, &if_not_smi_overflow);
+
+  assembler->Bind(&if_not_smi_overflow);
+  {
+    Node* result = assembler->ChangeInt32ToTagged(value);
+    assembler->Return(result);
+  }
+
+  assembler->Bind(&if_smi_overflow);
+  {
+    Node* float64_value = assembler->ChangeUint32ToFloat64(value);
+    Node* result = assembler->AllocateHeapNumberWithValue(float64_value);
+    assembler->Return(result);
+  }
+}
+
 void BitwiseOrStub::GenerateAssembly(
     compiler::CodeStubAssembler* assembler) const {
   using compiler::Node;