Cleanup RepresentationFromUseRequirements, move it to HValue and use it where relevant

src/hydrogen-instructions.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 66 matching lines @@
   }
 }
 
 
 void HValue::InferRepresentation(HInferRepresentation* h_infer) {
   ASSERT(CheckFlag(kFlexibleRepresentation));
   Representation new_rep = RepresentationFromInputs();
   UpdateRepresentation(new_rep, h_infer, "inputs");
   new_rep = RepresentationFromUses();
   UpdateRepresentation(new_rep, h_infer, "uses");
+  new_rep = RepresentationFromUseRequirements();
+  if (new_rep.fits_into(Representation::Integer32())) {
+    UpdateRepresentation(new_rep, h_infer, "use requirements");
+  }
 }
 
 
 Representation HValue::RepresentationFromUses() {
   if (HasNoUses()) return Representation::None();
 
   // Array of use counts for each representation.
   int use_count[Representation::kNumRepresentations] = { 0 };
 
   for (HUseIterator it(uses()); !it.Done(); it.Advance()) {
@@ skipping 2200 matching lines @@
 
 void HBinaryOperation::InferRepresentation(HInferRepresentation* h_infer) {
   ASSERT(CheckFlag(kFlexibleRepresentation));
   Representation new_rep = RepresentationFromInputs();
   UpdateRepresentation(new_rep, h_infer, "inputs");
   // When the operation has information about its own output type, don't look
   // at uses.
   if (!observed_output_representation_.IsNone()) return;
   new_rep = RepresentationFromUses();
   UpdateRepresentation(new_rep, h_infer, "uses");
+  new_rep = RepresentationFromUseRequirements();
+  if (new_rep.fits_into(Representation::Integer32())) {
+    UpdateRepresentation(new_rep, h_infer, "use requirements");
+  }
 }
 
 
 bool HBinaryOperation::IgnoreObservedOutputRepresentation(
     Representation current_rep) {
   return observed_output_representation_.IsDouble() &&
          current_rep.IsInteger32() &&
          // Mul in Integer32 mode would be too precise.
          !this->IsMul() &&
          CheckUsesForFlag(kTruncatingToInt32);
@@ skipping 1336 matching lines @@
 
 Representation HPhi::RepresentationFromInputs() {
   Representation r = Representation::None();
   for (int i = 0; i < OperandCount(); ++i) {
     r = r.generalize(OperandAt(i)->KnownOptimalRepresentation());
   }
   return r;
 }
 
 
-Representation HPhi::RepresentationFromUseRequirements() {
-  Representation all_uses_require = Representation::None();
-  bool all_uses_require_the_same = true;
+Representation HValue::RepresentationFromUseRequirements() {
+  Representation rep = Representation::None();
   for (HUseIterator it(uses()); !it.Done(); it.Advance()) {

[Jakob Kummerow, 2013/06/14 13:36:43]

Please add a high-level comment outlining the algorithm. E.g.:
// Check if all uses' requirements indicate that Integer32 is
// an appropriate representation for this value.

[Toon Verwaest, 2013/06/14 13:58:12]

Done.

     // We check for observed_input_representation elsewhere.
     Representation use_rep =
         it.value()->RequiredInputRepresentation(it.index());
-    // No useful info from this use -> look at the next one.
-    if (use_rep.IsNone()) {
+    if (rep.IsNone()) {
+      rep = use_rep;
       continue;
     }
-    if (use_rep.Equals(all_uses_require)) {
+    if (use_rep.IsNone() || rep.Equals(use_rep)) continue;
+    if (rep.generalize(use_rep).IsInteger32()) {
+      rep = Representation::Integer32();
       continue;
     }
-    // This use's representation contradicts what we've seen so far.
-    if (!all_uses_require.IsNone()) {
-      ASSERT(!use_rep.Equals(all_uses_require));
-      all_uses_require_the_same = false;
-      break;
-    }
-    // Otherwise, initialize observed representation.
-    all_uses_require = use_rep;
+    return Representation::None();
   }
-  if (all_uses_require_the_same) {
-    return all_uses_require;
-  }
-
-  return Representation::None();
+  return rep;
 }
 
 
 // Node-specific verification code is only included in debug mode.
 #ifdef DEBUG
 
 void HPhi::Verify() {
   ASSERT(OperandCount() == block()->predecessors()->length());
   for (int i = 0; i < OperandCount(); ++i) {
     HValue* value = OperandAt(i);
@@ skipping 154 matching lines @@
     case kBackingStore:
       if (!name_.is_null()) stream->Add(*String::cast(*name_)->ToCString());
       stream->Add("[backing-store]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal