[libcxx-commits] [libcxx] [libc++] Create a `constexpr` hash to use during constant evaluation (PR #214946)

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``````````bash
git-clang-format --diff origin/main HEAD --extensions h,cpp -- libcxx/test/support/constexpr_hash.h libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp libcxx/test/support/poisoned_hash_helper.h --diff_from_common_commit
``````````

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``````````diff
diff --git a/libcxx/test/support/constexpr_hash.h b/libcxx/test/support/constexpr_hash.h
index e298500f6..e3f335853 100644
--- a/libcxx/test/support/constexpr_hash.h
+++ b/libcxx/test/support/constexpr_hash.h
@@ -25,7 +25,7 @@ struct constexpr_hash;
 
 template <DisabledForHash _Tp>
 struct constexpr_hash<_Tp> {
-  constexpr_hash()                                   = delete;
+  constexpr_hash()                                 = delete;
   constexpr_hash(const constexpr_hash&)            = delete;
   constexpr_hash& operator=(const constexpr_hash&) = delete;
 };
@@ -46,29 +46,28 @@ struct constexpr_hash<_Tp> {
         return region[multiple - 1]; // TODO: hash-ing
       }
     } else if constexpr (std::is_floating_point_v<_Tp>) {
-    if (__v == 0.0f)
-      return 0;
-    // return __scalar_hash<_Tp>::operator()(__v);
+      if (__v == 0.0f)
+        return 0;
+      // return __scalar_hash<_Tp>::operator()(__v);
 
-        constexpr size_t multiple = sizeof(_Tp) / sizeof(char);
-        std::array<char, multiple> region = std::bit_cast<std::array<char, multiple>>(__v);
+      constexpr size_t multiple         = sizeof(_Tp) / sizeof(char);
+      std::array<char, multiple> region = std::bit_cast<std::array<char, multiple>>(__v);
 
-        // TODO: pack indexing?
-        size_t res = 0;
-        for(size_t i = 0; i < multiple; ++i) {
-            res ^= region[i];
-        }
-        return res;
-
-        // TODO: 0, 1, 2, 3, 4
-        // return region[multiple - 1]; // TODO: hash-ing
-        // return 1234ULL;
+      // TODO: pack indexing?
+      size_t res = 0;
+      for (size_t i = 0; i < multiple; ++i) {
+        res ^= region[i];
+      }
+      return res;
 
+      // TODO: 0, 1, 2, 3, 4
+      // return region[multiple - 1]; // TODO: hash-ing
+      // return 1234ULL;
     }
     __builtin_unreachable(); // todo: revisit
   }
 
-  constexpr_hash() noexcept                          = default;
+  constexpr_hash() noexcept                        = default;
   constexpr_hash& operator=(const constexpr_hash&) = default;
 };
 

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https://github.com/llvm/llvm-project/pull/214946