Backout changeset 06f92d065a85 (bug 1377333) because we don't need keys that are that big

xpcom/ds/PLDHashTable.cpp

@@ -72,7 +72,10 @@ PLDHashTable::HashStringKey(const void* aKey)
 /* static */ PLDHashNumber
 PLDHashTable::HashVoidPtrKeyStub(const void* aKey)
 {
-  return uintptr_t(aKey) >> 2;
+  // Be careful!  We don't want to do the cast to PLDHashNumber which is a
+  // trimming cast on 64-bit platforms before the shift, otherwise we will lose
+  // valuable bits from our hash key!
+  return PLDHashNumber(uintptr_t(aKey) >> 2);
 }
 
 /* static */ bool
@@ -255,10 +258,10 @@ PLDHashTable::Hash1(PLDHashNumber aHash0)
 
 void
 PLDHashTable::Hash2(PLDHashNumber aHash0,
-                    size_t& aHash2Out, size_t& aSizeMaskOut)
+                    uint32_t& aHash2Out, uint32_t& aSizeMaskOut)
 {
-  size_t sizeLog2 = kHashBits - mHashShift;
-  size_t sizeMask = (PLDHashNumber(1) << sizeLog2) - 1;
+  uint32_t sizeLog2 = kHashBits - mHashShift;
+  uint32_t sizeMask = (PLDHashNumber(1) << sizeLog2) - 1;
   aSizeMaskOut = sizeMask;
 
   // The incoming aHash0 always has the low bit unset (since we leave it
@@ -292,7 +295,7 @@ PLDHashTable::MatchEntryKeyhash(PLDHashEntryHdr* aEntry, PLDHashNumber aKeyHash)
 
 // Compute the address of the indexed entry in table.
 PLDHashEntryHdr*
-PLDHashTable::AddressEntry(size_t aIndex)
+PLDHashTable::AddressEntry(uint32_t aIndex)
 {
   return reinterpret_cast<PLDHashEntryHdr*>(
     mEntryStore.Get() + aIndex * mEntrySize);
@@ -370,7 +373,7 @@ PLDHashTable::SearchTable(const void* aKey, PLDHashNumber aKeyHash)
 
   // Collision: double hash.
   PLDHashNumber hash2;
-  size_t sizeMask;
+  uint32_t sizeMask;
   Hash2(aKeyHash, hash2, sizeMask);
 
   // Save the first removed entry pointer so Add() can recycle it. (Only used
@@ -430,7 +433,7 @@ PLDHashTable::FindFreeEntry(PLDHashNumber aKeyHash)
 
   // Collision: double hash.
   PLDHashNumber hash2;
-  size_t sizeMask;
+  uint32_t sizeMask;
   Hash2(aKeyHash, hash2, sizeMask);
 
   for (;;) {

xpcom/ds/PLDHashTable.h

@@ -15,7 +15,7 @@
 #include "mozilla/Types.h"
 #include "nscore.h"
 
-typedef size_t PLDHashNumber;
+typedef uint32_t PLDHashNumber;
 
 class PLDHashTable;
 struct PLDHashTableOps;
@@ -490,15 +490,10 @@ public:
   }
 
 private:
-  // Multiplicative hash uses an unsigned pointer sized integer and the golden ratio,
-  // expressed as a fixed-point pointer sized fraction.
-  static const uint32_t kHashBits = sizeof(size_t) * 8;
-#ifdef HAVE_64BIT_BUILD
-  // Golden ratio borrowed from http://burtleburtle.net/bob/hash/evahash.html.
-  static const uint64_t kGoldenRatio = 0X9E3779B97F4A7C13ULL;
-#else
+  // Multiplicative hash uses an unsigned 32 bit integer and the golden ratio,
+  // expressed as a fixed-point 32-bit fraction.
+  static const uint32_t kHashBits = 32;
   static const uint32_t kGoldenRatio = 0x9E3779B9U;
-#endif
 
   static uint32_t HashShift(uint32_t aEntrySize, uint32_t aLength);
 
@@ -527,10 +522,10 @@ private:
   }
 
   PLDHashNumber Hash1(PLDHashNumber aHash0);
-  void Hash2(PLDHashNumber aHash, size_t& aHash2Out, size_t& aSizeMaskOut);
+  void Hash2(PLDHashNumber aHash, uint32_t& aHash2Out, uint32_t& aSizeMaskOut);
 
   static bool MatchEntryKeyhash(PLDHashEntryHdr* aEntry, PLDHashNumber aHash);
-  PLDHashEntryHdr* AddressEntry(size_t aIndex);
+  PLDHashEntryHdr* AddressEntry(uint32_t aIndex);
 
   // We store mHashShift rather than sizeLog2 to optimize the collision-free
   // case in SearchTable.

xpcom/ds/nsPointerHashKeys.h

@@ -35,7 +35,10 @@ public:
   static KeyTypePointer KeyToPointer(KeyType aKey) { return aKey; }
   static PLDHashNumber HashKey(KeyTypePointer aKey)
   {
-    return uintptr_t(aKey) >> 2;
+    // Be careful!  We don't want to do the cast to PLDHashNumber which is a
+    // trimming cast on 64-bit platforms before the shift, otherwise we will
+    // lose valuable bits from our hash key!
+    return PLDHashNumber(uintptr_t(aKey) >> 2);
   }
   enum { ALLOW_MEMMOVE = true };