ShiftAmountsAllowReplaceByRotate Extension

src/hydrogen.cc

 // Copyright 2013 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 7590 matching lines @@
   BuildCheckHeapObject(string);
   HValue* checkstring =
       AddInstruction(HCheckInstanceType::NewIsString(string, zone()));
   HInstruction* length = BuildLoadStringLength(string, checkstring);
   AddInstruction(length);
   HInstruction* checked_index = Add<HBoundsCheck>(index, length);
   return New<HStringCharCodeAt>(string, checked_index);
 }
 
 
-// Checks if the given shift amounts have form: (sa) and (32 - sa).
+// Checks if the given shift amounts have following forms:
+// (N1) and (N2) with N1 + N2 = 32; (sa) and (32 - sa).
 static bool ShiftAmountsAllowReplaceByRotate(HValue* sa,
                                              HValue* const32_minus_sa) {
+  if (sa->IsConstant() && const32_minus_sa->IsConstant()) {
+    const HConstant* c1 = HConstant::cast(sa);
+    const HConstant* c2 = HConstant::cast(const32_minus_sa);
+    return c1->HasInteger32Value() && c2->HasInteger32Value() &&
+        (c1->Integer32Value() + c2->Integer32Value() == 32);
+  }
   if (!const32_minus_sa->IsSub()) return false;
   HSub* sub = HSub::cast(const32_minus_sa);
   if (sa != sub->right()) return false;
   HValue* const32 = sub->left();
   if (!const32->IsConstant() ||
       HConstant::cast(const32)->Integer32Value() != 32) {
     return false;
   }
   return (sub->right() == sa);
 }
@@ skipping 2055 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal