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

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index b36706b49b48119b6332a54e6782a9904e929ee5..b307a4c289586d526a7e73ca3ae80bb22f0d5d6d 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -84,6 +84,10 @@ void HValue::InferRepresentation(HInferRepresentation* h_infer) {
   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");
+  }
 }
 
 
@@ -2304,6 +2308,10 @@ void HBinaryOperation::InferRepresentation(HInferRepresentation* h_infer) {
   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");
+  }
 }
 
 
@@ -3660,34 +3668,24 @@ Representation HPhi::RepresentationFromInputs() {
 }
 
 
-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;
-  }
-  if (all_uses_require_the_same) {
-    return all_uses_require;
+    return Representation::None();
   }
-
-  return Representation::None();
+  return rep;
 }