[turboshaft] faster hash for GVN

Bug: v8:12783
Change-Id: I97f6a28bfef7c9aed679c84f33d60a71cf467718
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3859327
Reviewed-by: Darius Mercadier <dmercadier@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82865}

BUILD.bazel

@@ -2863,6 +2863,7 @@ filegroup(
         "src/compiler/turboshaft/decompression-optimization.cc",
         "src/compiler/turboshaft/decompression-optimization.h",
         "src/compiler/turboshaft/deopt-data.h",
+        "src/compiler/turboshaft/fast-hash.h",
         "src/compiler/turboshaft/graph-builder.cc",
         "src/compiler/turboshaft/graph-builder.h",
         "src/compiler/turboshaft/graph.cc",

BUILD.gn

@@ -2988,6 +2988,7 @@ v8_header_set("v8_internal_headers") {
     "src/compiler/turboshaft/assembler.h",
     "src/compiler/turboshaft/decompression-optimization.h",
     "src/compiler/turboshaft/deopt-data.h",
+    "src/compiler/turboshaft/fast-hash.h",
     "src/compiler/turboshaft/graph-builder.h",
     "src/compiler/turboshaft/graph-visualizer.h",
     "src/compiler/turboshaft/graph.h",

src/compiler/turboshaft/fast-hash.h

@@ -0,0 +1,73 @@
+// Copyright 2022 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_COMPILER_TURBOSHAFT_FAST_HASH_H_
+#define V8_COMPILER_TURBOSHAFT_FAST_HASH_H_
+
+#include <tuple>
+
+#include "src/base/functional.h"
+#include "src/base/vector.h"
+
+namespace v8::internal::compiler::turboshaft {
+
+// fast_hash_combine() / fast_hash_value() produce a bad but very fast to
+// compute hash, intended for hash-tables and only usable for data that is
+// sufficiently random already and has high variance in their low bits.
+
+V8_INLINE size_t fast_hash_combine() { return 0u; }
+V8_INLINE size_t fast_hash_combine(size_t acc) { return acc; }
+V8_INLINE size_t fast_hash_combine(size_t acc, size_t value) {
+  return 17 * acc + value;
+}
+template <typename T, typename... Ts>
+V8_INLINE size_t fast_hash_combine(T const& v, Ts const&... vs);
+
+template <class T>
+struct fast_hash {
+  size_t operator()(const T& v) {
+    if constexpr (std::is_enum<T>::value) {
+      return static_cast<size_t>(v);
+    } else {
+      return base::hash<T>()(v);
+    }
+  }
+};
+
+template <class... Ts>
+struct fast_hash<std::tuple<Ts...>> {
+  size_t operator()(const std::tuple<Ts...>& v) {
+    return impl(v, std::make_index_sequence<sizeof...(Ts)>());
+  }
+
+  template <size_t... I>
+  V8_INLINE size_t impl(std::tuple<Ts...> const& v, std::index_sequence<I...>) {
+    return fast_hash_combine(std::get<I>(v)...);
+  }
+};
+
+template <typename T, typename... Ts>
+V8_INLINE size_t fast_hash_combine(T const& v, Ts const&... vs) {
+  return fast_hash_combine(fast_hash_combine(vs...), fast_hash<T>()(v));
+}
+
+template <typename Iterator>
+V8_INLINE size_t fast_hash_range(Iterator first, Iterator last) {
+  size_t acc = 0;
+  for (; first != last; ++first) {
+    acc = fast_hash_combine(acc, *first);
+  }
+  return acc;
+}
+
+template <typename T>
+struct fast_hash<base::Vector<T>> {
+  V8_INLINE size_t operator()(base::Vector<T> v) {
+    return fast_hash_range(v.begin(), v.end());
+  }
+};
+
+}  // namespace v8::internal::compiler::turboshaft
+
+#endif  // V8_COMPILER_TURBOSHAFT_FAST_HASH_H_

src/compiler/turboshaft/operations.h

@@ -24,6 +24,7 @@
 #include "src/codegen/machine-type.h"
 #include "src/common/globals.h"
 #include "src/compiler/globals.h"
+#include "src/compiler/turboshaft/fast-hash.h"
 #include "src/compiler/turboshaft/utils.h"
 #include "src/compiler/write-barrier-kind.h"
 #include "src/zone/zone.h"
@@ -177,7 +178,10 @@ class OpIndex {
   static constexpr uint32_t kTurbofanNodeIdFlag = 1;
 };
 
-V8_INLINE size_t hash_value(OpIndex op) { return op.id(); }
+template <>
+struct fast_hash<OpIndex> {
+  V8_INLINE size_t operator()(OpIndex op) { return op.id(); }
+};
 
 // `BlockIndex` is the index of a bound block.
 // A dominating block always has a smaller index.
@@ -203,7 +207,10 @@ class BlockIndex {
   uint32_t id_;
 };
 
-V8_INLINE size_t hash_value(BlockIndex b) { return b.id(); }
+template <>
+struct fast_hash<BlockIndex> {
+  V8_INLINE size_t operator()(BlockIndex op) { return op.id(); }
+};
 
 std::ostream& operator<<(std::ostream& os, BlockIndex b);
 std::ostream& operator<<(std::ostream& os, const Block* b);
@@ -419,7 +426,7 @@ struct OperationT : Operation {
            derived_this().options() == other.derived_this().options();
   }
   size_t hash_value() const {
-    return base::hash_combine(opcode, derived_this().inputs(),
+    return fast_hash_combine(opcode, derived_this().inputs(),
                              derived_this().options());
   }
 
@@ -1154,17 +1161,17 @@ struct ConstantOp : FixedArityOperationT<0, ConstantOp> {
       case Kind::kWord32:
       case Kind::kWord64:
       case Kind::kTaggedIndex:
-        return base::hash_combine(kind, storage.integral);
+        return fast_hash_combine(opcode, kind, storage.integral);
       case Kind::kFloat32:
-        return base::hash_combine(kind, storage.float32);
+        return fast_hash_combine(opcode, kind, storage.float32);
       case Kind::kFloat64:
       case Kind::kNumber:
-        return base::hash_combine(kind, storage.float64);
+        return fast_hash_combine(opcode, kind, storage.float64);
       case Kind::kExternal:
-        return base::hash_combine(kind, storage.external.address());
+        return fast_hash_combine(opcode, kind, storage.external.address());
       case Kind::kHeapObject:
       case Kind::kCompressedHeapObject:
-        return base::hash_combine(kind, storage.handle.address());
+        return fast_hash_combine(opcode, kind, storage.handle.address());
     }
   }
   bool operator==(const ConstantOp& other) const {
@@ -1563,9 +1570,7 @@ struct SwitchOp : FixedArityOperationT<1, SwitchOp> {
 
     Case(int32_t value, Block* destination)
         : value(value), destination(destination) {}
-    friend size_t hash_value(Case v) {
-      return base::hash_combine(v.value, v.destination);
-    }
+
     bool operator==(const Case& other) const {
       return value == other.value && destination == other.destination;
     }
@@ -1583,6 +1588,13 @@ struct SwitchOp : FixedArityOperationT<1, SwitchOp> {
   auto options() const { return std::tuple{cases, default_case}; }
 };
 
+template <>
+struct fast_hash<SwitchOp::Case> {
+  size_t operator()(SwitchOp::Case v) {
+    return fast_hash_combine(v.value, v.destination);
+  }
+};
+
 // Tuples are only used to lower operations with multiple outputs.
 // `TupleOp` should be folded away by subsequent `ProjectionOp`s.
 struct TupleOp : OperationT<TupleOp> {

src/compiler/turboshaft/value-numbering-assembler.h

@@ -8,6 +8,7 @@
 #include "src/base/logging.h"
 #include "src/base/vector.h"
 #include "src/compiler/turboshaft/assembler.h"
+#include "src/compiler/turboshaft/fast-hash.h"
 #include "src/compiler/turboshaft/graph.h"
 #include "src/compiler/turboshaft/operations.h"
 #include "src/utils/utils.h"
@@ -239,7 +240,7 @@ class ValueNumberingAssembler : public Assembler {
   size_t ComputeHash(const Op& op) {
     size_t hash = op.hash_value();
     if (same_block_only) {
-      hash = base::hash_combine(current_block()->index(), hash);
+      hash = fast_hash_combine(current_block()->index(), hash);
     }
     if (V8_UNLIKELY(hash == 0)) return 1;
     return hash;