A64: Synchronize with r17441.

src/hydrogen-canonicalize.cc

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 #include "hydrogen-canonicalize.h"
+#include "hydrogen-redundant-phi.h"
 
 namespace v8 {
 namespace internal {
 
 void HCanonicalizePhase::Run() {
   const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
   // Before removing no-op instructions, save their semantic value.
   // We must be careful not to set the flag unnecessarily, because GVN
   // cannot identify two instructions when their flag value differs.
   for (int i = 0; i < blocks->length(); ++i) {
@@ skipping 11 matching lines @@
             instr->SetFlag(HInstruction::kAllUsesTruncatingToSmi);
           } else if (instr->HasAtLeastOneUseWithFlagAndNoneWithout(
                          HInstruction::kTruncatingToInt32)) {
             // Avoid redundant minus zero check
             instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32);
           }
         }
       }
     }
   }
+
   // Perform actual Canonicalization pass.
+  HRedundantPhiEliminationPhase redundant_phi_eliminator(graph());
   for (int i = 0; i < blocks->length(); ++i) {
+    // Eliminate redundant phis in the block first; changes to their inputs
+    // might have made them redundant, and eliminating them creates more
+    // opportunities for constant folding and strength reduction.
+    redundant_phi_eliminator.ProcessBlock(blocks->at(i));
+    // Now canonicalize each instruction.
     for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
       HInstruction* instr = it.Current();
       HValue* value = instr->Canonicalize();
       if (value != instr) instr->DeleteAndReplaceWith(value);
     }
   }
 }
 
 } }  // namespace v8::internal