8305896: Alternative full GC forwarding

src/hotspot/share/gc/shared/slidingForwarding.cpp

@@ -26,6 +26,7 @@
 #include "precompiled.hpp"
 #include "gc/shared/gc_globals.hpp"
 #include "gc/shared/slidingForwarding.hpp"
+#include "utilities/fastHash.hpp"
 #include "utilities/ostream.hpp"
 #include "utilities/powerOfTwo.hpp"
 
@@ -123,19 +124,7 @@ FallbackTable::~FallbackTable() {
 
 size_t FallbackTable::home_index(HeapWord* from) {
   uint64_t val = reinterpret_cast<uint64_t>(from);
-  // This is the mixer stage of the murmur3 hashing:
-  // https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp
-  val ^= val >> 33;
-  val *= 0xff51afd7ed558ccdULL;
-  val ^= val >> 33;
-  val *= 0xc4ceb9fe1a85ec53ULL;
-  val ^= val >> 33;
-  // Shift to table-size.
-  val = val >> (64 - log2i_exact(TABLE_SIZE));
-  size_t idx = static_cast<size_t>(val);
-  assert(idx < TABLE_SIZE, "must fit in table: idx: " SIZE_FORMAT ", table-size: %u, table-size-bits: %d",
-         idx, TABLE_SIZE, log2i_exact(TABLE_SIZE));
-  return idx;
+  return FastHash::get_hash64(val, 0xAAAAAAAAAAAAAAAA);
 }
 
 void FallbackTable::forward_to(HeapWord* from, HeapWord* to) {

src/hotspot/share/utilities/fastHash.hpp

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "memory/allStatic.hpp"
+
+class FastHash : public AllStatic {
+private:
+  static void fullmul64(uint64_t& hi, uint64_t& lo, uint64_t op1, uint64_t op2) {
+#if defined(__SIZEOF_INT128__)
+    __uint128_t prod = static_cast<__uint128_t>(op1) * static_cast<__uint128_t>(op2);
+    hi = static_cast<uint64_t>(prod >> 64);
+    lo = static_cast<uint64_t>(prod >>  0);
+#else
+    /* First calculate all of the cross products. */
+    uint64_t lo_lo = (op1 & 0xFFFFFFFF) * (op2 & 0xFFFFFFFF);
+    uint64_t hi_lo = (op1 >> 32)        * (op2 & 0xFFFFFFFF);
+    uint64_t lo_hi = (op1 & 0xFFFFFFFF) * (op2 >> 32);
+    uint64_t hi_hi = (op1 >> 32)        * (op2 >> 32);
+
+    /* Now add the products together. These will never overflow. */
+    uint64_t cross = (lo_lo >> 32) + (hi_lo & 0xFFFFFFFF) + lo_hi;
+    uint64_t upper = (hi_lo >> 32) + (cross >> 32)        + hi_hi;
+    hi = upper;
+    lo = (cross << 32) | (lo_lo & 0xFFFFFFFF);
+#endif
+  }
+
+  static void fullmul32(uint32_t& hi, uint32_t& lo, uint32_t op1, uint32_t op2) {
+    uint64_t x64 = op1, y64 = op2, xy64 = x64 * y64;
+    hi = (uint32_t)(xy64 >> 32);
+    lo = (uint32_t)(xy64 >>  0);
+  }
+
+  static uint64_t ror(uint64_t x, uint64_t distance) {
+    distance = distance & 0x3F;
+    return (x >> distance) | (x << (64 - distance));
+  }
+
+public:
+  static uint64_t get_hash64(uint64_t x, uint64_t y) {
+    const uint64_t M  = 0x8ADAE89C337954D5;
+    const uint64_t A  = 0xAAAAAAAAAAAAAAAA; // REPAA
+    const uint64_t H0 = (x ^ y), L0 = (x ^ A);
+
+    uint64_t U0, V0; fullmul64(U0, V0, L0, M);
+    const uint64_t Q0 = (H0 * M);
+    const uint64_t L1 = (Q0 ^ U0);
+
+    uint64_t U1, V1; fullmul64(U1, V1, L1, M);
+    const uint64_t P1 = (V0 ^ M);
+    const uint64_t Q1 = ror(P1, L1);
+    const uint64_t L2 = (Q1 ^ U1);
+    return V1 ^ L2;
+  }
+
+  static uint32_t get_hash32(uint32_t x, uint32_t y) {
+    const uint32_t M  = 0x337954D5;
+    const uint32_t A  = 0xAAAAAAAA; // REPAA
+    const uint32_t H0 = (x ^ y), L0 = (x ^ A);
+
+    uint32_t U0, V0; fullmul32(U0, V0, L0, M);
+    const uint32_t Q0 = (H0 * M);
+    const uint32_t L1 = (Q0 ^ U0);
+
+    uint32_t U1, V1; fullmul32(U1, V1, L1, M);
+    const uint32_t P1 = (V0 ^ M);
+    const uint32_t Q1 = ror(P1, L1);
+    const uint32_t L2 = (Q1 ^ U1);
+    return V1 ^ L2;
+  }
+};