Merge ConstantInstr -> UnboxDouble to UnboxedConstant. Reduces register usage and allows for variou…

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/intermediate_language.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/bit_vector.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
@@ skipping 307 matching lines @@
 }
 
 
 bool ConstantInstr::AttributesEqual(Instruction* other) const {
   ConstantInstr* other_constant = other->AsConstant();
   ASSERT(other_constant != NULL);
   return (value().raw() == other_constant->value().raw());
 }
 
 
+UnboxedConstantInstr::UnboxedConstantInstr(const Object& value)
+    : ConstantInstr(value), constant_address_(NULL) {
+  // Only doubles supported for now.
+  ASSERT(value.IsDouble());
+  constant_address_ =
+      FlowGraphBuilder::FindDoubleConstant(Double::Cast(value).value());
+}
+
 // Returns true if the value represents a constant.
 bool Value::BindsToConstant() const {
   return definition()->IsConstant();
 }
 
 
 // Returns true if the value represents constant null.
 bool Value::BindsToConstantNull() const {
   ConstantInstr* constant = definition()->AsConstant();
   return (constant != NULL) && constant->value().IsNull();
@@ skipping 879 matching lines @@
   return Utils::IsPowerOfTwo(Utils::Abs(int_value));
 }
 
 
 static bool ToIntegerConstant(Value* value, intptr_t* result) {
   if (!value->BindsToConstant()) {
     if (value->definition()->IsUnboxDouble()) {
       return ToIntegerConstant(value->definition()->AsUnboxDouble()->value(),
                                result);
     }
-
     return false;
   }
 
   const Object& constant = value->BoundConstant();
   if (constant.IsDouble()) {
     const Double& double_constant = Double::Cast(constant);
     *result = static_cast<intptr_t>(double_constant.value());
     return (static_cast<double>(*result) == double_constant.value());
   } else if (constant.IsSmi()) {
     *result = Smi::Cast(constant).Value();
@@ skipping 355 matching lines @@
   // Fold away BoxDouble(UnboxDouble(v)) if value is known to be double.
   UnboxDoubleInstr* defn = value()->definition()->AsUnboxDouble();
   if ((defn != NULL) && (defn->value()->Type()->ToCid() == kDoubleCid)) {
     return defn->value()->definition();
   }
 
   return this;
 }
 
 
 Definition* UnboxDoubleInstr::Canonicalize(FlowGraph* flow_graph) {

[Florian Schneider, 2014/05/01 18:34:16]

Maybe add

if (!HasUses()) return NULL;

so that Unbox operations that are not used anymore after canonicalization get
removed in a following pass.

[srdjan, 2014/05/01 20:33:04]

Done.

   // Fold away UnboxDouble(BoxDouble(v)).
-  BoxDoubleInstr* defn = value()->definition()->AsBoxDouble();
-  return (defn != NULL) ? defn->value()->definition() : this;
+  BoxDoubleInstr* box_defn = value()->definition()->AsBoxDouble();
+  if (box_defn != NULL) {
+    return box_defn->value()->definition();
+  }
+
+  ConstantInstr* c = value()->definition()->AsConstant();
+  if ((c != NULL) && c->value().IsDouble()) {
+    UnboxedConstantInstr* uc = new UnboxedConstantInstr(c->value());
+    flow_graph->InsertBefore(this, uc, this->env(), Definition::kValue);

[Florian Schneider, 2014/05/01 18:34:16]

UnboxedConstant should not need an environment, since it can't deoptimize and
can't become a deoptimization target. I'd pass NULL instead of this->env().

[srdjan, 2014/05/01 20:33:04]

Done.

+    return uc;

[Florian Schneider, 2014/05/01 18:34:16]

Make sure that the UnboxDoubleInstr get removed by the optimizer after the new
UnboxedConstant is inserted. It should not have any uses after this Canonicalize
step, so it can be just removed from the graph.

[srdjan, 2014/05/01 20:33:04]

I checked it visually in disassembled output/flow graph. Any other way?

+  }
+
+  return this;
 }
 
 
 Definition* BoxFloat32x4Instr::Canonicalize(FlowGraph* flow_graph) {
   if (input_use_list() == NULL) {
     // Environments can accomodate any representation. No need to box.
     return value()->definition();
   }
 
   // Fold away BoxFloat32x4(UnboxFloat32x4(v)).
@@ skipping 1721 matching lines @@
     case Token::kTRUNCDIV: return 0;
     case Token::kMOD: return 1;
     default: UNIMPLEMENTED(); return -1;
   }
 }
 
 
 #undef __
 
 }  // namespace dart