Only assign environments when they are actually needed. (ia32 only)

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 987 matching lines @@
 
 LInstruction* LChunkBuilder::DoGoto(HGoto* instr) {
   return new(zone()) LGoto(instr->FirstSuccessor());
 }
 
 
 LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
   LInstruction* goto_instr = CheckElideControlInstruction(instr);
   if (goto_instr != NULL) return goto_instr;
 
+  HValue* value = instr->value();
+  Representation r = value->representation();
+  HType type = value->type();
   ToBooleanStub::Types expected = instr->expected_input_types();
+  if (expected.IsEmpty()) expected = ToBooleanStub::Types::Generic();
 
-  // Tagged values that are not known smis or booleans require a
-  // deoptimization environment. If the instruction is generic no
-  // environment is needed since all cases are handled.
-  HValue* value = instr->value();
-  Representation rep = value->representation();
-  HType type = value->type();
-  if (!rep.IsTagged() || type.IsSmi() || type.IsBoolean()) {
-    return new(zone()) LBranch(UseRegister(value), NULL);
+  bool easy_case = !r.IsTagged() || type.IsBoolean() || type.IsSmi() ||
+      type.IsJSArray() || type.IsHeapNumber() || type.IsString();
+  LOperand* temp = !easy_case && expected.NeedsMap() ? TempRegister() : NULL;
+  LInstruction* branch = new(zone()) LBranch(UseRegister(value), temp);
+  if (!easy_case &&
+      ((!expected.Contains(ToBooleanStub::SMI) && expected.NeedsMap()) ||
+       !expected.IsGeneric())) {
+    branch = AssignEnvironment(branch);
   }
-
-  bool needs_temp = expected.NeedsMap() || expected.IsEmpty();
-  LOperand* temp = needs_temp ? TempRegister() : NULL;
-
-  // The Generic stub does not have a deopt, so we need no environment.
-  if (expected.IsGeneric()) {
-    return new(zone()) LBranch(UseRegister(value), temp);
-  }
-
-  // We need a temporary register when we have to access the map *or* we have
-  // no type info yet, in which case we handle all cases (including the ones
-  // involving maps).
-  return AssignEnvironment(new(zone()) LBranch(UseRegister(value), temp));
+  return branch;
 }
 
 
 LInstruction* LChunkBuilder::DoDebugBreak(HDebugBreak* instr) {
   return new(zone()) LDebugBreak();
 }
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
   LInstruction* goto_instr = CheckElideControlInstruction(instr);
@@ skipping 172 matching lines @@
   LOperand* input = UseRegister(instr->value());
   LOperand* temp = FixedTemp(xmm4);
   LMathRound* result = new(zone()) LMathRound(input, temp);
   return AssignEnvironment(DefineAsRegister(result));
 }
 
 
 LInstruction* LChunkBuilder::DoMathAbs(HUnaryMathOperation* instr) {
   LOperand* context = UseAny(instr->context());  // Deferred use.
   LOperand* input = UseRegisterAtStart(instr->value());
-  LMathAbs* result = new(zone()) LMathAbs(context, input);
-  return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
+  LInstruction* result =
+      DefineSameAsFirst(new(zone()) LMathAbs(context, input));
+  Representation r = instr->value()->representation();
+  if (!r.IsDouble() && !r.IsSmiOrInteger32()) result = AssignPointerMap(result);
+  if (!r.IsDouble()) result = AssignEnvironment(result);
+  return result;
 }
 
 
 LInstruction* LChunkBuilder::DoMathLog(HUnaryMathOperation* instr) {
   ASSERT(instr->representation().IsDouble());
   ASSERT(instr->value()->representation().IsDouble());
   LOperand* input = UseRegisterAtStart(instr->value());
   return MarkAsCall(DefineSameAsFirst(new(zone()) LMathLog(input)), instr);
 }
 
@@ skipping 658 matching lines @@
     from = Representation::Tagged();
   }
   // Only mark conversions that might need to allocate as calling rather than
   // all changes. This makes simple, non-allocating conversion not have to force
   // building a stack frame.
   if (from.IsTagged()) {
     if (to.IsDouble()) {
       LOperand* value = UseRegister(instr->value());
       // Temp register only necessary for minus zero check.
       LOperand* temp = TempRegister();
-      LNumberUntagD* res = new(zone()) LNumberUntagD(value, temp);
-      return AssignEnvironment(DefineAsRegister(res));
+      LInstruction* result = DefineAsRegister(
+          new(zone()) LNumberUntagD(value, temp));
+      if (!instr->value()->representation().IsSmi()) {
+        result = AssignEnvironment(result);
+      }
+      return result;
     } else if (to.IsSmi()) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
       if (val->type().IsSmi()) {
         return DefineSameAsFirst(new(zone()) LDummyUse(value));
       }
       return AssignEnvironment(DefineSameAsFirst(new(zone()) LCheckSmi(value)));
     } else {
       ASSERT(to.IsInteger32());
       HValue* val = instr->value();
       if (val->type().IsSmi() || val->representation().IsSmi()) {
         LOperand* value = UseRegister(val);
         return DefineSameAsFirst(new(zone()) LSmiUntag(value, false));
       } else {
         bool truncating = instr->CanTruncateToInt32();
         LOperand* xmm_temp =
             (CpuFeatures::IsSafeForSnapshot(SSE2) && !truncating)
                 ? FixedTemp(xmm1) : NULL;
-        LTaggedToI* res = new(zone()) LTaggedToI(UseRegister(val), xmm_temp);
-        return AssignEnvironment(DefineSameAsFirst(res));
+        LInstruction* result = DefineSameAsFirst(
+            new(zone()) LTaggedToI(UseRegister(val), xmm_temp));
+        if (!instr->value()->representation().IsSmi()) {
+          // Note: Only deopts in deferred code.
+          result = AssignEnvironment(result);
+        }
+        return result;
       }
     }
   } else if (from.IsDouble()) {
     if (to.IsTagged()) {
       info()->MarkAsDeferredCalling();
       LOperand* value = UseRegisterAtStart(instr->value());
       LOperand* temp = FLAG_inline_new ? TempRegister() : NULL;
 
       // Make sure that temp and result_temp are different registers.
       LUnallocated* result_temp = TempRegister();
       LNumberTagD* result = new(zone()) LNumberTagD(value, temp);
       return AssignPointerMap(Define(result, result_temp));
     } else if (to.IsSmi()) {
       LOperand* value = UseRegister(instr->value());
       return AssignEnvironment(
           DefineAsRegister(new(zone()) LDoubleToSmi(value)));
     } else {
       ASSERT(to.IsInteger32());
       bool truncating = instr->CanTruncateToInt32();
       bool needs_temp = CpuFeatures::IsSafeForSnapshot(SSE2) && !truncating;
       LOperand* value = needs_temp ?
           UseTempRegister(instr->value()) : UseRegister(instr->value());
       LOperand* temp = needs_temp ? TempRegister() : NULL;
-      return AssignEnvironment(
-          DefineAsRegister(new(zone()) LDoubleToI(value, temp)));
+      LInstruction* result =
+          DefineAsRegister(new(zone()) LDoubleToI(value, temp));
+      if (!truncating) result = AssignEnvironment(result);
+      return result;
     }
   } else if (from.IsInteger32()) {
     info()->MarkAsDeferredCalling();
     if (to.IsTagged()) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
       if (!instr->CheckFlag(HValue::kCanOverflow)) {
         return DefineSameAsFirst(new(zone()) LSmiTag(value));
       } else if (val->CheckFlag(HInstruction::kUint32)) {
         LOperand* temp1 = TempRegister();
         LOperand* temp2 = CpuFeatures::IsSupported(SSE2) ? FixedTemp(xmm1)
                                                          : NULL;
         LNumberTagU* result = new(zone()) LNumberTagU(value, temp1, temp2);
-        return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
+        return AssignPointerMap(DefineSameAsFirst(result));
       } else {
         LOperand* temp = TempRegister();
         LNumberTagI* result = new(zone()) LNumberTagI(value, temp);
-        return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
+        return AssignPointerMap(DefineSameAsFirst(result));
       }
     } else if (to.IsSmi()) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
       LInstruction* result = DefineSameAsFirst(new(zone()) LSmiTag(value));
       if (instr->CheckFlag(HValue::kCanOverflow)) {
         result = AssignEnvironment(result);
       }
       return result;
     } else {
@@ skipping 45 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoCheckMaps(HCheckMaps* instr) {
   LOperand* value = NULL;
   if (!instr->CanOmitMapChecks()) {
     value = UseRegisterAtStart(instr->value());
     if (instr->has_migration_target()) info()->MarkAsDeferredCalling();
   }
   LCheckMaps* result = new(zone()) LCheckMaps(value);
   if (!instr->CanOmitMapChecks()) {
+    // Note: Only deopts in deferred code.
     AssignEnvironment(result);
     if (instr->has_migration_target()) return AssignPointerMap(result);
   }
   return result;
 }
 
 
 LInstruction* LChunkBuilder::DoClampToUint8(HClampToUint8* instr) {
   HValue* value = instr->value();
   Representation input_rep = value->representation();
@@ skipping 88 matching lines @@
   LStoreGlobalCell* result =
       new(zone()) LStoreGlobalCell(UseRegister(instr->value()));
   return instr->RequiresHoleCheck() ? AssignEnvironment(result) : result;
 }
 
 
 LInstruction* LChunkBuilder::DoLoadContextSlot(HLoadContextSlot* instr) {
   LOperand* context = UseRegisterAtStart(instr->value());
   LInstruction* result =
       DefineAsRegister(new(zone()) LLoadContextSlot(context));
-  return instr->RequiresHoleCheck() ? AssignEnvironment(result) : result;
+  if (instr->RequiresHoleCheck() && instr->DeoptimizesOnHole()) {
+    result = AssignEnvironment(result);
+  }
+  return result;
 }
 
 
 LInstruction* LChunkBuilder::DoStoreContextSlot(HStoreContextSlot* instr) {
   LOperand* value;
   LOperand* temp;
   LOperand* context = UseRegister(instr->context());
   if (instr->NeedsWriteBarrier()) {
     value = UseTempRegister(instr->value());
     temp = TempRegister();
   } else {
     value = UseRegister(instr->value());
     temp = NULL;
   }
   LInstruction* result = new(zone()) LStoreContextSlot(context, value, temp);
-  return instr->RequiresHoleCheck() ? AssignEnvironment(result) : result;
+  if (instr->RequiresHoleCheck() && instr->DeoptimizesOnHole()) {
+    result = AssignEnvironment(result);
+  }
+  return result;
 }
 
 
 LInstruction* LChunkBuilder::DoLoadNamedField(HLoadNamedField* instr) {
   LOperand* obj = (instr->access().IsExternalMemory() &&
                    instr->access().offset() == 0)
       ? UseRegisterOrConstantAtStart(instr->object())
       : UseRegisterAtStart(instr->object());
   return DefineAsRegister(new(zone()) LLoadNamedField(obj));
 }
@@ skipping 21 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed* instr) {
   ASSERT(instr->key()->representation().IsSmiOrInteger32());
   ElementsKind elements_kind = instr->elements_kind();
   bool clobbers_key = ExternalArrayOpRequiresTemp(
       instr->key()->representation(), elements_kind);
   LOperand* key = clobbers_key
       ? UseTempRegister(instr->key())
       : UseRegisterOrConstantAtStart(instr->key());
-  LLoadKeyed* result = NULL;
+  LInstruction* result = NULL;
 
   if (!instr->is_typed_elements()) {
     LOperand* obj = UseRegisterAtStart(instr->elements());
-    result = new(zone()) LLoadKeyed(obj, key);
+    result = DefineAsRegister(new(zone()) LLoadKeyed(obj, key));
   } else {
     ASSERT(
         (instr->representation().IsInteger32() &&
          !(IsDoubleOrFloatElementsKind(instr->elements_kind()))) ||
         (instr->representation().IsDouble() &&
          (IsDoubleOrFloatElementsKind(instr->elements_kind()))));
     LOperand* backing_store = UseRegister(instr->elements());
-    result = new(zone()) LLoadKeyed(backing_store, key);
+    result = DefineAsRegister(new(zone()) LLoadKeyed(backing_store, key));
   }
 
-  DefineAsRegister(result);
-  bool can_deoptimize = instr->RequiresHoleCheck() ||
-      (elements_kind == EXTERNAL_UINT32_ELEMENTS);
-  // An unsigned int array load might overflow and cause a deopt, make sure it
-  // has an environment.
-  return can_deoptimize ? AssignEnvironment(result) : result;
+  if ((instr->is_external() || instr->is_fixed_typed_array()) ?
+      // see LCodeGen::DoLoadKeyedExternalArray
+      ((instr->elements_kind() == EXTERNAL_UINT32_ELEMENTS ||
+        instr->elements_kind() == UINT32_ELEMENTS) &&
+       !instr->CheckFlag(HInstruction::kUint32)) :
+      // see LCodeGen::DoLoadKeyedFixedDoubleArray and
+      // LCodeGen::DoLoadKeyedFixedArray
+      instr->RequiresHoleCheck()) {
+    result = AssignEnvironment(result);
+  }
+  return result;
 }
 
 
 LInstruction* LChunkBuilder::DoLoadKeyedGeneric(HLoadKeyedGeneric* instr) {
   LOperand* context = UseFixed(instr->context(), esi);
   LOperand* object = UseFixed(instr->object(), edx);
   LOperand* key = UseFixed(instr->key(), ecx);
 
   LLoadKeyedGeneric* result =
       new(zone()) LLoadKeyedGeneric(context, object, key);
@@ skipping 170 matching lines @@
   }
 
   // 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 = (!is_in_object || needs_write_barrier ||
                     needs_write_barrier_for_map) ? TempRegister() : NULL;
 
   // We need a temporary register for write barrier of the map field.
   LOperand* temp_map = needs_write_barrier_for_map ? TempRegister() : NULL;
 
-  LStoreNamedField* result =
+  LInstruction* result =
       new(zone()) LStoreNamedField(obj, val, temp, temp_map);
-  if (instr->field_representation().IsHeapObject()) {
-    if (!instr->value()->type().IsHeapObject()) {
-      return AssignEnvironment(result);
-    }
+  if (!instr->access().IsExternalMemory() &&
+      instr->field_representation().IsHeapObject() &&
+      (val->IsConstantOperand()
+       ? HConstant::cast(instr->value())->HasSmiValue()
+       : !instr->value()->type().IsHeapObject())) {
+    result = AssignEnvironment(result);
   }
   return result;
 }
 
 
 LInstruction* LChunkBuilder::DoStoreNamedGeneric(HStoreNamedGeneric* instr) {
   LOperand* context = UseFixed(instr->context(), esi);
   LOperand* object = UseFixed(instr->object(), edx);
   LOperand* value = UseFixed(instr->value(), eax);
 
@@ skipping 11 matching lines @@
   return MarkAsCall(DefineFixed(string_add, eax), instr);
 }
 
 
 LInstruction* LChunkBuilder::DoStringCharCodeAt(HStringCharCodeAt* instr) {
   LOperand* string = UseTempRegister(instr->string());
   LOperand* index = UseTempRegister(instr->index());
   LOperand* context = UseAny(instr->context());
   LStringCharCodeAt* result =
       new(zone()) LStringCharCodeAt(context, string, index);
-  return AssignEnvironment(AssignPointerMap(DefineAsRegister(result)));
+  return AssignPointerMap(DefineAsRegister(result));
 }
 
 
 LInstruction* LChunkBuilder::DoStringCharFromCode(HStringCharFromCode* instr) {
   LOperand* char_code = UseRegister(instr->value());
   LOperand* context = UseAny(instr->context());
   LStringCharFromCode* result =
       new(zone()) LStringCharFromCode(context, char_code);
   return AssignPointerMap(DefineAsRegister(result));
 }
@@ skipping 222 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