Eliminate write barrier for global stores at compile time if value stored is a smi.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
===================================================================
--- src/x64/lithium-codegen-x64.cc	(revision 9605)
+++ src/x64/lithium-codegen-x64.cc	(working copy)
@@ -2055,19 +2055,24 @@
   // Store the value.
   __ movq(Operand(address, 0), value);
 
-  Label smi_store;
-  __ JumpIfSmi(value, &smi_store, Label::kNear);
+  if (instr->hydrogen()->NeedsWriteBarrier()) {
+    Label smi_store;
+    HType type = instr->hydrogen()->value()->type();
+    if (!type.IsHeapNumber() && !type.IsString() && !type.IsNonPrimitive()) {
+      __ JumpIfSmi(value, &smi_store, Label::kNear);
+    }
 
-  int offset = JSGlobalPropertyCell::kValueOffset - kHeapObjectTag;
-  __ lea(object, Operand(address, -offset));
-  // Cells are always in the remembered set.
-  __ RecordWrite(object,
-                 address,
-                 value,
-                 kSaveFPRegs,
-                 OMIT_REMEMBERED_SET,
-                 OMIT_SMI_CHECK);
-  __ bind(&smi_store);
+    int offset = JSGlobalPropertyCell::kValueOffset - kHeapObjectTag;
+    __ lea(object, Operand(address, -offset));
+    // Cells are always in the remembered set.
+    __ RecordWrite(object,
+                   address,
+                   value,
+                   kSaveFPRegs,
+                   OMIT_REMEMBERED_SET,
+                   OMIT_SMI_CHECK);
+    __ bind(&smi_store);
+  }
 }
 
 
@@ -2094,10 +2099,19 @@
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
   __ movq(ContextOperand(context, instr->slot_index()), value);
-  if (instr->needs_write_barrier()) {
+  if (instr->hydrogen()->NeedsWriteBarrier()) {
+    HType type = instr->hydrogen()->value()->type();
+    SmiCheck check_needed =
+        type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
     int offset = Context::SlotOffset(instr->slot_index());
     Register scratch = ToRegister(instr->TempAt(0));
-    __ RecordWriteContextSlot(context, offset, value, scratch, kSaveFPRegs);
+    __ RecordWriteContextSlot(context,
+                              offset,
+                              value,
+                              scratch,
+                              kSaveFPRegs,
+                              EMIT_REMEMBERED_SET,
+                              check_needed);
   }
 }
 
@@ -3061,21 +3075,36 @@
   }
 
   // Do the store.
+  HType type = instr->hydrogen()->value()->type();
+  SmiCheck check_needed =
+      type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
   if (instr->is_in_object()) {
     __ movq(FieldOperand(object, offset), value);
-    if (instr->needs_write_barrier()) {
+    if (instr->hydrogen()->NeedsWriteBarrier()) {
       Register temp = ToRegister(instr->TempAt(0));
       // Update the write barrier for the object for in-object properties.
-      __ RecordWriteField(object, offset, value, temp, kSaveFPRegs);
+      __ RecordWriteField(object,
+                          offset,
+                          value,
+                          temp,
+                          kSaveFPRegs,
+                          EMIT_REMEMBERED_SET,
+                          check_needed);
     }
   } else {
     Register temp = ToRegister(instr->TempAt(0));
     __ movq(temp, FieldOperand(object, JSObject::kPropertiesOffset));
     __ movq(FieldOperand(temp, offset), value);
-    if (instr->needs_write_barrier()) {
+    if (instr->hydrogen()->NeedsWriteBarrier()) {
       // Update the write barrier for the properties array.
       // object is used as a scratch register.
-      __ RecordWriteField(temp, offset, value, object, kSaveFPRegs);
+      __ RecordWriteField(temp,
+                          offset,
+                          value,
+                          object,
+                          kSaveFPRegs,
+                          EMIT_REMEMBERED_SET,
+                          check_needed);
     }
   }
 }
@@ -3182,12 +3211,20 @@
   }
 
   if (instr->hydrogen()->NeedsWriteBarrier()) {
+    HType type = instr->hydrogen()->value()->type();
+    SmiCheck check_needed =
+        type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
     // Compute address of modified element and store it into key register.
     __ lea(key, FieldOperand(elements,
                              key,
                              times_pointer_size,
                              FixedArray::kHeaderSize));
-    __ RecordWrite(elements, key, value, kSaveFPRegs);
+    __ RecordWrite(elements,
+                   key,
+                   value,
+                   kSaveFPRegs,
+                   EMIT_REMEMBERED_SET,
+                   check_needed);
   }
 }
 
@@ -3975,12 +4012,11 @@
   Label* true_label = chunk_->GetAssemblyLabel(true_block);
   Label* false_label = chunk_->GetAssemblyLabel(false_block);
 
-  Condition final_branch_condition = EmitTypeofIs(true_label,
-                                                  false_label,
-                                                  input,
-                                                  instr->type_literal());
-
-  EmitBranch(true_block, false_block, final_branch_condition);
+  Condition final_branch_condition =
+      EmitTypeofIs(true_label, false_label, input, instr->type_literal());
+  if (final_branch_condition != no_condition) {
+    EmitBranch(true_block, false_block, final_branch_condition);
+  }
 }
 
 
@@ -4048,7 +4084,6 @@
     final_branch_condition = zero;
 
   } else {
-    final_branch_condition = never;
     __ jmp(false_label);
   }