[llvm] r341113 - Hashing: use 64-bit seed for hashing on all platforms.

[Tim Northover via llvm-commits]

Author: tnorthover
Date: Thu Aug 30 13:28:32 2018
New Revision: 341113

URL: http://llvm.org/viewvc/llvm-project?rev=341113&view=rev
Log:
Hashing: use 64-bit seed for hashing on all platforms.

get_execution_seed returns a size_t which varies across platforms, but its
users actually always feed it into a uint64_t role so it makes sense to be
consistent.

Mostly this is just a tidy-up, but it also apparently allows PCH files to be
shared between Clang compilers built for 32-bit and 64-bit hosts.

Modified:
    llvm/trunk/include/llvm/ADT/Hashing.h
    llvm/trunk/lib/Support/Hashing.cpp

Modified: llvm/trunk/include/llvm/ADT/Hashing.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/Hashing.h?rev=341113&r1=341112&r2=341113&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/Hashing.h (original)
+++ llvm/trunk/include/llvm/ADT/Hashing.h Thu Aug 30 13:28:32 2018
@@ -133,7 +133,7 @@ hash_code hash_value(const std::basic_st
 /// undone. This makes it thread-hostile and very hard to use outside of
 /// immediately on start of a simple program designed for reproducible
 /// behavior.
-void set_fixed_execution_hash_seed(size_t fixed_value);
+void set_fixed_execution_hash_seed(uint64_t fixed_value);
 
 
 // All of the implementation details of actually computing the various hash
@@ -316,9 +316,9 @@ struct hash_state {
 /// This variable can be set using the \see llvm::set_fixed_execution_seed
 /// function. See that function for details. Do not, under any circumstances,
 /// set or read this variable.
-extern size_t fixed_seed_override;
+extern uint64_t fixed_seed_override;
 
-inline size_t get_execution_seed() {
+inline uint64_t get_execution_seed() {
   // FIXME: This needs to be a per-execution seed. This is just a placeholder
   // implementation. Switching to a per-execution seed is likely to flush out
   // instability bugs and so will happen as its own commit.
@@ -326,8 +326,7 @@ inline size_t get_execution_seed() {
   // However, if there is a fixed seed override set the first time this is
   // called, return that instead of the per-execution seed.
   const uint64_t seed_prime = 0xff51afd7ed558ccdULL;
-  static size_t seed = fixed_seed_override ? fixed_seed_override
-                                           : (size_t)seed_prime;
+  static uint64_t seed = fixed_seed_override ? fixed_seed_override : seed_prime;
   return seed;
 }
 
@@ -402,7 +401,7 @@ bool store_and_advance(char *&buffer_ptr
 /// combining them, this (as an optimization) directly combines the integers.
 template <typename InputIteratorT>
 hash_code hash_combine_range_impl(InputIteratorT first, InputIteratorT last) {
-  const size_t seed = get_execution_seed();
+  const uint64_t seed = get_execution_seed();
   char buffer[64], *buffer_ptr = buffer;
   char *const buffer_end = std::end(buffer);
   while (first != last && store_and_advance(buffer_ptr, buffer_end,
@@ -446,7 +445,7 @@ hash_code hash_combine_range_impl(InputI
 template <typename ValueT>
 typename std::enable_if<is_hashable_data<ValueT>::value, hash_code>::type
 hash_combine_range_impl(ValueT *first, ValueT *last) {
-  const size_t seed = get_execution_seed();
+  const uint64_t seed = get_execution_seed();
   const char *s_begin = reinterpret_cast<const char *>(first);
   const char *s_end = reinterpret_cast<const char *>(last);
   const size_t length = std::distance(s_begin, s_end);
@@ -496,7 +495,7 @@ namespace detail {
 struct hash_combine_recursive_helper {
   char buffer[64];
   hash_state state;
-  const size_t seed;
+  const uint64_t seed;
 
 public:
   /// Construct a recursive hash combining helper.

Modified: llvm/trunk/lib/Support/Hashing.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Hashing.cpp?rev=341113&r1=341112&r2=341113&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Hashing.cpp (original)
+++ llvm/trunk/lib/Support/Hashing.cpp Thu Aug 30 13:28:32 2018
@@ -20,10 +20,10 @@ using namespace llvm;
 // Provide a definition and static initializer for the fixed seed. This
 // initializer should always be zero to ensure its value can never appear to be
 // non-zero, even during dynamic initialization.
-size_t llvm::hashing::detail::fixed_seed_override = 0;
+uint64_t llvm::hashing::detail::fixed_seed_override = 0;
 
 // Implement the function for forced setting of the fixed seed.
 // FIXME: Use atomic operations here so that there is no data race.
-void llvm::set_fixed_execution_hash_seed(size_t fixed_value) {
+void llvm::set_fixed_execution_hash_seed(uint64_t fixed_value) {
   hashing::detail::fixed_seed_override = fixed_value;
 }