Lithium: avoid registers for constants when possible.

src/ia32/lithium-ia32.cc

 // Copyright 2012 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 583 matching lines @@
 }
 
 
 LOperand* LChunkBuilder::UseRegisterOrConstantAtStart(HValue* value) {
   return value->IsConstant()
       ? chunk_->DefineConstantOperand(HConstant::cast(value))
       : UseRegisterAtStart(value);
 }
 
 
+LOperand* LChunkBuilder::UseConstant(HValue* value) {
+  return chunk_->DefineConstantOperand(HConstant::cast(value));
+}
+
+
 LOperand* LChunkBuilder::UseAny(HValue* value) {
   return value->IsConstant()
       ? chunk_->DefineConstantOperand(HConstant::cast(value))
       :  Use(value, new(zone()) LUnallocated(LUnallocated::ANY));
 }
 
 
 LOperand* LChunkBuilder::Use(HValue* value, LUnallocated* operand) {
   if (value->EmitAtUses()) {
     HInstruction* instr = HInstruction::cast(value);
@@ skipping 1666 matching lines @@
 
   if (!CpuFeatures::IsSafeForSnapshot(SSE2) &&
       IsDoubleOrFloatElementsKind(elements_kind)) {
     return UseRegisterAtStart(instr->value());
   }
 
   return UseRegister(instr->value());
 }
 
 
-// DoStoreKeyed and DoStoreNamedField have special considerations for allowing
-// use of a constant instead of a register.
-static bool StoreConstantValueAllowed(HValue* value) {
-  if (value->IsConstant()) {
-    HConstant* constant_value = HConstant::cast(value);
-    return constant_value->HasSmiValue()
-        || constant_value->HasDoubleValue()
-        || constant_value->ImmortalImmovable();
-  }
-  return false;
-}
-
-
 LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
   if (!instr->is_external()) {
     ASSERT(instr->elements()->representation().IsTagged());
     ASSERT(instr->key()->representation().IsInteger32() ||
            instr->key()->representation().IsTagged());
 
     if (instr->value()->representation().IsDouble()) {
       LOperand* object = UseRegisterAtStart(instr->elements());
       LOperand* val = NULL;
       if (CpuFeatures::IsSafeForSnapshot(SSE2)) {
         val = UseRegisterAtStart(instr->value());
       } else if (!instr->IsConstantHoleStore()) {
         val = UseX87TopOfStack(instr->value());
       }
       LOperand* key = UseRegisterOrConstantAtStart(instr->key());
       return new(zone()) LStoreKeyed(object, key, val);
     } else {
       ASSERT(instr->value()->representation().IsTagged());
       bool needs_write_barrier = instr->NeedsWriteBarrier();
 
       LOperand* obj = UseRegister(instr->elements());
       LOperand* val;
       LOperand* key;
       if (needs_write_barrier) {
         val = UseTempRegister(instr->value());
         key = UseTempRegister(instr->key());
       } else {
-        if (StoreConstantValueAllowed(instr->value())) {
-          val = UseRegisterOrConstantAtStart(instr->value());
-        } else {
-          val = UseRegisterAtStart(instr->value());
-        }
-
-        if (StoreConstantValueAllowed(instr->key())) {
-          key = UseRegisterOrConstantAtStart(instr->key());
-        } else {
-          key = UseRegisterAtStart(instr->key());
-        }
+        val = UseRegisterOrConstantAtStart(instr->value());
+        key = UseRegisterOrConstantAtStart(instr->key());
       }
       return new(zone()) LStoreKeyed(obj, key, val);
     }
   }
 
   ElementsKind elements_kind = instr->elements_kind();
   ASSERT(
       (instr->value()->representation().IsInteger32() &&
        (elements_kind != EXTERNAL_FLOAT_ELEMENTS) &&
        (elements_kind != EXTERNAL_DOUBLE_ELEMENTS)) ||
@@ skipping 80 matching lines @@
   if (needs_write_barrier) {
     obj = instr->is_in_object()
         ? UseRegister(instr->object())
         : UseTempRegister(instr->object());
   } else {
     obj = needs_write_barrier_for_map
         ? UseRegister(instr->object())
         : UseRegisterAtStart(instr->object());
   }
 
+  bool can_be_constant = instr->value()->IsConstant() &&
+      !HConstant::cast(instr->value())->InNewSpace();
+
   LOperand* val;
   if (needs_write_barrier) {
     val = UseTempRegister(instr->value());
-  } else if (StoreConstantValueAllowed(instr->value())) {
+  } else if (can_be_constant) {
     val = UseRegisterOrConstant(instr->value());
   } else {
     val = UseRegister(instr->value());
   }
 
   // We only need a scratch register if we have a write barrier or we
   // have a store into the properties array (not in-object-property).
   LOperand* temp = (!instr->is_in_object() || needs_write_barrier ||
       needs_write_barrier_for_map) ? TempRegister() : NULL;
 
@@ skipping 54 matching lines @@
   LOperand* context = UseAny(instr->context());
   LOperand* temp = TempRegister();
   LAllocateObject* result = new(zone()) LAllocateObject(context, temp);
   return AssignPointerMap(DefineAsRegister(result));
 }
 
 
 LInstruction* LChunkBuilder::DoAllocate(HAllocate* instr) {
   info()->MarkAsDeferredCalling();
   LOperand* context = UseAny(instr->context());
-  // TODO(mvstanton): why can't size be a constant if possible?
-  LOperand* size = UseTempRegister(instr->size());
+  LOperand* size = instr->size()->IsConstant()
+      ? UseConstant(instr->size())
+      : UseTempRegister(instr->size());
   LOperand* temp = TempRegister();
   LAllocate* result = new(zone()) LAllocate(context, size, temp);
   return AssignPointerMap(DefineAsRegister(result));
 }
 
 
 LInstruction* LChunkBuilder::DoArrayLiteral(HArrayLiteral* instr) {
   LOperand* context = UseFixed(instr->context(), esi);
   return MarkAsCall(
       DefineFixed(new(zone()) LArrayLiteral(context), eax), instr);
@@ skipping 243 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32