[hydrogen] don't bailout assignments to consts

src/arm/lithium-codegen-arm.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2288 matching lines @@
 }
 
 
 void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register result = ToRegister(instr->result());
   __ ldr(result, ContextOperand(context, instr->slot_index()));
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
     __ cmp(result, ip);
-    DeoptimizeIf(eq, instr->environment());
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(eq, instr->environment());
+    } else {

[Steven, 2011/12/12 13:12:44]

You can do better here and use a conditional move instead:
__ mov(result, Operand(factory()->undefined_value()), LeaveCC, eq);

+      Label is_not_hole;
+      __ b(ne, &is_not_hole);
+
+      __ mov(result, Operand(factory()->undefined_value()));
+
+      __ bind(&is_not_hole);
+    }
   }
 }
 
 
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+  Register scratch = scratch0();
   MemOperand target = ContextOperand(context, instr->slot_index());
+
+  Label skip_assignment;
+
   if (instr->hydrogen()->RequiresHoleCheck()) {
-    Register scratch = scratch0();
     __ ldr(scratch, target);
     __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
     __ cmp(scratch, ip);
-    DeoptimizeIf(eq, instr->environment());
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(eq, instr->environment());
+    } else {
+      __ b(ne, &skip_assignment);
+    }
   }
+
   __ str(value, target);
   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(),
+                              scratch,
                               kLRHasBeenSaved,
                               kSaveFPRegs,
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }
 
 
 void LCodeGen::DoLoadNamedField(LLoadNamedField* instr) {
   Register object = ToRegister(instr->InputAt(0));
   Register result = ToRegister(instr->result());
   if (instr->hydrogen()->is_in_object()) {
     __ ldr(result, FieldMemOperand(object, instr->hydrogen()->offset()));
   } else {
     __ ldr(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
@@ skipping 2365 matching lines @@
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 
 
 #undef __
 
 } }  // namespace v8::internal