Unroll more StringDictionary lookup probes both for positive and negative dictionary lookups.

src/x64/ic-x64.cc

 // Copyright 2011 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 79 matching lines @@
                      (1 << Map::kHasNamedInterceptor)));
   __ j(not_zero, miss);
 
   __ movq(r0, FieldOperand(receiver, JSObject::kPropertiesOffset));
   __ CompareRoot(FieldOperand(r0, HeapObject::kMapOffset),
                  Heap::kHashTableMapRootIndex);
   __ j(not_equal, miss);
 }
 
 
-// Probe the string dictionary in the |elements| register. Jump to the
-// |done| label if a property with the given name is found leaving the
-// index into the dictionary in |r1|. Jump to the |miss| label
-// otherwise.
-static void GenerateStringDictionaryProbes(MacroAssembler* masm,
-                                           Label* miss,
-                                           Label* done,
-                                           Register elements,
-                                           Register name,
-                                           Register r0,
-                                           Register r1) {
-  // Assert that name contains a string.
-  if (FLAG_debug_code) __ AbortIfNotString(name);
-
-  // Compute the capacity mask.
-  const int kCapacityOffset =
-      StringDictionary::kHeaderSize +
-      StringDictionary::kCapacityIndex * kPointerSize;
-  __ SmiToInteger32(r0, FieldOperand(elements, kCapacityOffset));
-  __ decl(r0);
-
-  // Generate an unrolled loop that performs a few probes before
-  // giving up. Measurements done on Gmail indicate that 2 probes
-  // cover ~93% of loads from dictionaries.
-  static const int kProbes = 4;
-  const int kElementsStartOffset =
-      StringDictionary::kHeaderSize +
-      StringDictionary::kElementsStartIndex * kPointerSize;
-  for (int i = 0; i < kProbes; i++) {
-    // Compute the masked index: (hash + i + i * i) & mask.
-    __ movl(r1, FieldOperand(name, String::kHashFieldOffset));
-    __ shrl(r1, Immediate(String::kHashShift));
-    if (i > 0) {
-      __ addl(r1, Immediate(StringDictionary::GetProbeOffset(i)));
-    }
-    __ and_(r1, r0);
-
-    // Scale the index by multiplying by the entry size.
-    ASSERT(StringDictionary::kEntrySize == 3);
-    __ lea(r1, Operand(r1, r1, times_2, 0));  // r1 = r1 * 3
-
-    // Check if the key is identical to the name.
-    __ cmpq(name, Operand(elements, r1, times_pointer_size,
-                          kElementsStartOffset - kHeapObjectTag));
-    if (i != kProbes - 1) {
-      __ j(equal, done);
-    } else {
-      __ j(not_equal, miss);
-    }
-  }
-}
-
 
 // Helper function used to load a property from a dictionary backing storage.
 // This function may return false negatives, so miss_label
 // must always call a backup property load that is complete.
 // This function is safe to call if name is not a symbol, and will jump to
 // the miss_label in that case.
 // The generated code assumes that the receiver has slow properties,
 // is not a global object and does not have interceptors.
 static void GenerateDictionaryLoad(MacroAssembler* masm,
                                    Label* miss_label,
@@ skipping 10 matching lines @@
   //
   // r0   - used to hold the capacity of the property dictionary.
   //
   // r1   - used to hold the index into the property dictionary.
   //
   // result - holds the result on exit if the load succeeded.
 
   Label done;
 
   // Probe the dictionary.
-  GenerateStringDictionaryProbes(masm,
-                                 miss_label,
-                                 &done,
-                                 elements,
-                                 name,
-                                 r0,
-                                 r1);
+  StringDictionaryLookupStub::GeneratePositiveLookup(masm,
+                                                     miss_label,
+                                                     &done,
+                                                     elements,
+                                                     name,
+                                                     r0,
+                                                     r1);
 
   // If probing finds an entry in the dictionary, r0 contains the
   // index into the dictionary. Check that the value is a normal
   // property.
   __ bind(&done);
   const int kElementsStartOffset =
       StringDictionary::kHeaderSize +
       StringDictionary::kElementsStartIndex * kPointerSize;
   const int kDetailsOffset = kElementsStartOffset + 2 * kPointerSize;
   __ Test(Operand(elements, r1, times_pointer_size,
@@ skipping 31 matching lines @@
   //
   // value - holds the value to store and is unchanged.
   //
   // scratch0 - used for index into the property dictionary and is clobbered.
   //
   // scratch1 - used to hold the capacity of the property dictionary and is
   //            clobbered.
   Label done;
 
   // Probe the dictionary.
-  GenerateStringDictionaryProbes(masm,
-                                 miss_label,
-                                 &done,
-                                 elements,
-                                 name,
-                                 scratch0,
-                                 scratch1);
+   StringDictionaryLookupStub::GeneratePositiveLookup(masm,
+                                                      miss_label,
+                                                      &done,
+                                                      elements,
+                                                      name,
+                                                      scratch0,
+                                                      scratch1);
 
   // If probing finds an entry in the dictionary, scratch0 contains the
   // index into the dictionary. Check that the value is a normal
   // property that is not read only.
   __ bind(&done);
   const int kElementsStartOffset =
       StringDictionary::kHeaderSize +
       StringDictionary::kElementsStartIndex * kPointerSize;
   const int kDetailsOffset = kElementsStartOffset + 2 * kPointerSize;
   const int kTypeAndReadOnlyMask
@@ skipping 1352 matching lines @@
   Condition cc = *jmp_address == Assembler::kJncShortOpcode
       ? not_zero
       : zero;
   *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64