Infrastructure classes for evaluating numeric relations between values.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index b353cdb2cc514acd7f31bc1752c92faff3f10ff7..47df208c3b4d700d2ab13d5cc7692102f074ebfe 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -405,9 +405,10 @@ bool HValue::TestDominanceUsingProcessedFlag(HValue* dominator,
   if (dominator->block() != dominated->block()) {
     return dominator->block()->Dominates(dominated->block());
   } else {
-    // If both arguments are in the same block we check if "dominator" has
-    // already been processed or if it is a phi: if yes it dominates the other.
-    return dominator->CheckFlag(kIDefsProcessingDone) || dominator->IsPhi();
+    // If both arguments are in the same block we check if dominator is a phi
+    // or if dominated has not already been processed: in either case we know
+    // that dominator precedes dominated.
+    return dominator->IsPhi() || !dominated->CheckFlag(kIDefsProcessingDone);
   }
 }
 
@@ -524,6 +525,16 @@ const char* HValue::Mnemonic() const {
 }
 
 
+bool HValue::IsInteger32Constant() {
+  return IsConstant() && HConstant::cast(this)->HasInteger32Value();
+}
+
+
+int32_t HValue::GetInteger32Constant() {
+  return HConstant::cast(this)->Integer32Value();
+}
+
+
 void HValue::SetOperandAt(int index, HValue* value) {
   RegisterUse(index, value);
   InternalSetOperandAt(index, value);
@@ -794,6 +805,37 @@ void HInstruction::Verify() {
 #endif
 
 
+HNumericConstraint* HNumericConstraint::AddToGraph(
+    HValue* constrained_value,
+    NumericRelation relation,
+    HValue* related_value,
+    HInstruction* insertion_point) {
+  if (insertion_point == NULL) {
+    if (constrained_value->IsInstruction()) {
+      insertion_point = HInstruction::cast(constrained_value);
+    } else if (constrained_value->IsPhi()) {
+      insertion_point = constrained_value->block()->first();
+    } else {
+      UNREACHABLE();
+    }
+  }
+  HNumericConstraint* result =
+      new(insertion_point->block()->zone()) HNumericConstraint(
+          constrained_value, relation, related_value);
+  result->InsertAfter(insertion_point);
+  return result;
+}
+
+
+void HNumericConstraint::PrintDataTo(StringStream* stream) {
+  stream->Add("(");
+  constrained_value()->PrintNameTo(stream);
+  stream->Add(" %s ", relation().Mnemonic());
+  related_value()->PrintNameTo(stream);
+  stream->Add(")");
+}
+
+
 void HDummyUse::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
 }
@@ -815,10 +857,36 @@ void HBinaryCall::PrintDataTo(StringStream* stream) {
 }
 
 
+void HBoundsCheck::AddInformativeDefinitions() {

[Jakob Kummerow, 2013/02/13 13:20:56]

Please add a comment here:
  // TODO(mmassi): Executing this code during AddInformativeDefinitions
  // is a hack. Move it to some other HPhase.

+  if (index()->IsRelationTrue(NumericRelation::Ge(),
+                              block()->graph()->GetConstant0()) &&
+      index()->IsRelationTrue(NumericRelation::Lt(), length())) {
+    set_skip_check(true);
+  }
+}
+
+
+bool HBoundsCheck::IsRelationTrueInternal(NumericRelation relation,
+                                          HValue* related_value) {
+  if (related_value == length()) {
+    // A HBoundsCheck is smaller than the length it compared against.
+    return NumericRelation::Lt().Implies(relation);
+  } else if (related_value == block()->graph()->GetConstant0()) {
+    // A HBoundsCheck is greater than or equal to zero.
+    return NumericRelation::Ge().Implies(relation);
+  } else {
+    return false;
+  }
+}
+
+
 void HBoundsCheck::PrintDataTo(StringStream* stream) {
   index()->PrintNameTo(stream);
   stream->Add(" ");
   length()->PrintNameTo(stream);
+  if (skip_check()) {
+    stream->Add(" [DISABLED]");
+  }
 }
 
 
@@ -1475,6 +1543,36 @@ Range* HMod::InferRange(Zone* zone) {
 }
 
 
+void HPhi::AddInformativeDefinitions() {
+  if (OperandCount() == 2) {
+    for (int operand_index = 0; operand_index < 2; operand_index++) {
+      int other_operand_index = (operand_index + 1) % 2;
+
+      // Add an idef that "discards" the OSR entry block branch.
+      if (OperandAt(operand_index)->block()->is_osr_entry()) {
+        HNumericConstraint::AddToGraph(
+              this, NumericRelation::Eq(), OperandAt(other_operand_index));

[Jakob Kummerow, 2013/02/13 13:20:56]

nit: 4 spaces indentation is enough

+      }
+
+      static NumericRelation relations[] = {
+        NumericRelation::Ge(),
+        NumericRelation::Le()
+      };
+
+      // Check if this phi is an induction variable.

[Jakob Kummerow, 2013/02/13 13:20:56]

Please extend this comment to convey the reasoning behind the code:
      // Check if this phi is an induction variable. If, e.g., we know that
      // its first input is greater than the phi itself, then that must be
      // the back edge, and the phi is always greater than its second input.

+      for (int relation_index = 0; relation_index < 2; relation_index++) {
+        if (OperandAt(operand_index)->IsRelationTrue(relations[relation_index],
+                                                     this)) {
+          HNumericConstraint::AddToGraph(this,
+                                         relations[relation_index],
+                                         OperandAt(other_operand_index));
+        }
+      }
+    }
+  }
+}
+
+
 Range* HMathMinMax::InferRange(Zone* zone) {
   if (representation().IsInteger32()) {
     Range* a = left()->range();
@@ -1888,6 +1986,7 @@ Range* HShr::InferRange(Zone* zone) {
 }
 
 
+

[Jakob Kummerow, 2013/02/13 13:20:56]

nit: unneeded whitespace

 Range* HShl::InferRange(Zone* zone) {
   if (right()->IsConstant()) {
     HConstant* c = HConstant::cast(right());
@@ -1936,6 +2035,16 @@ void HStringCompareAndBranch::PrintDataTo(StringStream* stream) {
 }
 
 
+void HCompareIDAndBranch::AddInformativeDefinitions() {
+  NumericRelation r = NumericRelation::FromToken(token());
+  if (r.IsNone()) return;
+
+  HNumericConstraint::AddToGraph(left(), r, right(), SuccessorAt(0)->first());
+  HNumericConstraint::AddToGraph(
+        left(), r.Negated(), right(), SuccessorAt(1)->first());
+}
+
+
 void HCompareIDAndBranch::PrintDataTo(StringStream* stream) {
   stream->Add(Token::Name(token()));
   stream->Add(" ");