Base iDef update code.

src/hydrogen.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 3569 matching lines @@
   if (FLAG_use_range) {
     HRangeAnalysis rangeAnalysis(this);
     rangeAnalysis.Analyze();
   }
   ComputeMinusZeroChecks();
 
   // Eliminate redundant stack checks on backwards branches.
   HStackCheckEliminator sce(this);
   sce.Process();
 
-  if (FLAG_array_bounds_checks_elimination) EliminateRedundantBoundsChecks();
+  if (FLAG_idefs) SetupInformativeDefinitions();
+  if (FLAG_array_bounds_checks_elimination && !FLAG_idefs) {
+    EliminateRedundantBoundsChecks();
+  }
   if (FLAG_array_index_dehoisting) DehoistSimpleArrayIndexComputations();
   if (FLAG_dead_code_elimination) DeadCodeElimination();
 
   RestoreActualValues();
 
   return true;
 }
 
 
+void HGraph::SetupInformativeDefinitionsInBlock(HBasicBlock* block) {
+  for (int phi_index = 0; phi_index < block->phis()->length(); phi_index++) {
+    HPhi* phi = block->phis()->at(phi_index);
+    phi->AddInformativeDefinitions();
+    // We do not support phis that "redefine just one operand".
+    ASSERT(!phi->IsInformativeDefinition());
+  }
+
+  for (HInstruction* i = block->first(); i != NULL; i = i->next()) {
+    i->AddInformativeDefinitions();
+    i->UpdateRedefinedUsesWhileSettingUpInformativeDefinitions();
+  }
+}
+
+
+// This method is recursive, so if its stack frame is large it could
+// cause a stack overflow.
+// To keep the individual stack frames small we do the actual work inside
+// SetupInformativeDefinitionsInBlock();
+void HGraph::SetupInformativeDefinitionsRecursively(HBasicBlock* block) {
+  SetupInformativeDefinitionsInBlock(block);
+  for (int i = 0; i < block->dominated_blocks()->length(); ++i) {
+    SetupInformativeDefinitionsRecursively(block->dominated_blocks()->at(i));
+  }
+}
+
+
+void HGraph::SetupInformativeDefinitions() {
+  HPhase phase("H_Setup informative definitions", this);
+  SetupInformativeDefinitionsRecursively(entry_block());
+}
+
+
 // We try to "factor up" HBoundsCheck instructions towards the root of the
 // dominator tree.
 // For now we handle checks where the index is like "exp + int32value".
 // If in the dominator tree we check "exp + v1" and later (dominated)
 // "exp + v2", if v2 <= v1 we can safely remove the second check, and if
 // v2 > v1 we can use v2 in the 1st check and again remove the second.
 // To do so we keep a dictionary of all checks where the key if the pair
 // "exp, length".
 // The class BoundsCheckKey represents this key.
 class BoundsCheckKey : public ZoneObject {
@@ skipping 6738 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal