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

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
===================================================================
--- src/arm/lithium-codegen-arm.cc	(revision 9605)
+++ src/arm/lithium-codegen-arm.cc	(working copy)
@@ -2251,13 +2251,19 @@
   __ str(value, FieldMemOperand(scratch, JSGlobalPropertyCell::kValueOffset));
 
   // Cells are always in the remembered set.
-  __ RecordWriteField(scratch,
-                      JSGlobalPropertyCell::kValueOffset,
-                      value,
-                      scratch2,
-                      kLRHasBeenSaved,
-                      kSaveFPRegs,
-                      OMIT_REMEMBERED_SET);
+  if (instr->hydrogen()->NeedsWriteBarrier()) {
+    HType type = instr->hydrogen()->value()->type();
+    SmiCheck check_needed =
+        type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
+    __ RecordWriteField(scratch,
+                        JSGlobalPropertyCell::kValueOffset,
+                        value,
+                        scratch2,
+                        kLRHasBeenSaved,
+                        kSaveFPRegs,
+                        OMIT_REMEMBERED_SET,
+                        check_needed);
+  }
 }
 
 
@@ -2285,13 +2291,18 @@
   Register value = ToRegister(instr->value());
   MemOperand target = ContextOperand(context, instr->slot_index());
   __ str(value, target);
-  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;
     __ RecordWriteContextSlot(context,
                               target.offset(),
                               value,
                               scratch0(),
                               kLRHasBeenSaved,
-                              kSaveFPRegs);
+                              kSaveFPRegs,
+                              EMIT_REMEMBERED_SET,
+                              check_needed);
   }
 }
 
@@ -3297,21 +3308,26 @@
   }
 
   // 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()) {
     __ str(value, FieldMemOperand(object, offset));
-    if (instr->needs_write_barrier()) {
+    if (instr->hydrogen()->NeedsWriteBarrier()) {
       // Update the write barrier for the object for in-object properties.
       __ RecordWriteField(
-          object, offset, value, scratch, kLRHasBeenSaved, kSaveFPRegs);
+          object, offset, value, scratch, kLRHasBeenSaved, kSaveFPRegs,

[Vyacheslav Egorov (Chromium), 2011/10/13 14:07:57]

argument per line

+          EMIT_REMEMBERED_SET, check_needed);
     }
   } else {
     __ ldr(scratch, FieldMemOperand(object, JSObject::kPropertiesOffset));
     __ str(value, FieldMemOperand(scratch, offset));
-    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(

[Vyacheslav Egorov (Chromium), 2011/10/13 14:07:57]

argument per line

-          scratch, offset, value, object, kLRHasBeenSaved, kSaveFPRegs);
+          scratch, offset, value, object, kLRHasBeenSaved, kSaveFPRegs,
+          EMIT_REMEMBERED_SET, check_needed);
     }
   }
 }
@@ -3362,9 +3378,13 @@
   }
 
   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.
     __ add(key, scratch, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
-    __ RecordWrite(elements, key, value, kLRHasBeenSaved, kSaveFPRegs);
+    __ RecordWrite(elements, key, value, kLRHasBeenSaved, kSaveFPRegs,

[Vyacheslav Egorov (Chromium), 2011/10/13 14:07:57]

ditto

+                   EMIT_REMEMBERED_SET, check_needed);
   }
 }
 
@@ -4349,8 +4369,9 @@
                                                   false_label,
                                                   input,
                                                   instr->type_literal());
-
-  EmitBranch(true_block, false_block, final_branch_condition);
+  if (final_branch_condition != kNoCondition) {
+    EmitBranch(true_block, false_block, final_branch_condition);
+  }
 }
 
 
@@ -4420,9 +4441,7 @@
     final_branch_condition = eq;
 
   } else {
-    final_branch_condition = ne;
     __ b(false_label);
-    // A dead branch instruction will be generated after this point.
   }
 
   return final_branch_condition;