P3008R6 Atomic floating-point min/max

Author: jensmaurer

source/numerics.tex

@@ -9664,6 +9664,11 @@
   constexpr float               fminf(float x, float y);
   constexpr long double         fminl(long double x, long double y);
 
+  constexpr @\placeholdernc{floating-point-type}@ fmaximum(@\placeholdernc{floating-point-type}@ x, @\placeholdernc{floating-point-type}@ y);
+  constexpr @\placeholdernc{floating-point-type}@ fmaximum_num(@\placeholdernc{floating-point-type}@ x, @\placeholdernc{floating-point-type}@ y);
+  constexpr @\placeholdernc{floating-point-type}@ fminimum(@\placeholdernc{floating-point-type}@ x, @\placeholdernc{floating-point-type}@ y);
+  constexpr @\placeholdernc{floating-point-type}@ fminimum_num(@\placeholdernc{floating-point-type}@ x, @\placeholdernc{floating-point-type}@ y);
+
   constexpr @\placeholdernc{floating-point-type}@ fma(@\placeholdernc{floating-point-type}@ x, @\placeholdernc{floating-point-type}@ y,
                                     @\placeholdernc{floating-point-type}@ z);
   constexpr float               fmaf(float x, float y, float z);

source/support.tex

@@ -590,7 +590,7 @@
 #define @\defnlibxname{cpp_lib_atomic_float}@                      201711L // freestanding, also in \libheader{atomic}
 #define @\defnlibxname{cpp_lib_atomic_is_always_lock_free}@        201603L // freestanding, also in \libheader{atomic}
 #define @\defnlibxname{cpp_lib_atomic_lock_free_type_aliases}@     201907L // also in \libheader{atomic}
-#define @\defnlibxname{cpp_lib_atomic_min_max}@                    202403L // freestanding, also in \libheader{atomic}
+#define @\defnlibxname{cpp_lib_atomic_min_max}@                    202506L // freestanding, also in \libheader{atomic}
 #define @\defnlibxname{cpp_lib_atomic_ref}@                        202411L // freestanding, also in \libheader{atomic}
 #define @\defnlibxname{cpp_lib_atomic_shared_ptr}@                 201711L // also in \libheader{memory}
 #define @\defnlibxname{cpp_lib_atomic_value_initialization}@       201911L // freestanding, also in \libheader{atomic}, \libheader{memory}

source/threads.tex

@@ -3773,6 +3773,19 @@
     constexpr value_type fetch_sub(value_type,
                                   memory_order = memory_order::seq_cst) const noexcept;
 
+    constexpr @\placeholdernc{floating-point-type}@ fetch_max(@\placeholdernc{floating-point-type}@,
+                              memory_order = memory_order::seq_cst) const noexcept;
+    constexpr @\placeholdernc{floating-point-type}@ fetch_min(@\placeholdernc{floating-point-type}@,
+                              memory_order = memory_order::seq_cst) const noexcept;
+    constexpr @\placeholdernc{floating-point-type}@ fetch_fmaximum(@\placeholdernc{floating-point-type}@,
+                              memory_order = memory_order::seq_cst) const noexcept;
+    constexpr @\placeholdernc{floating-point-type}@ fetch_fminimum(@\placeholdernc{floating-point-type}@,
+                              memory_order = memory_order::seq_cst) const noexcept;
+    constexpr @\placeholdernc{floating-point-type}@ fetch_fmaximum_num(@\placeholdernc{floating-point}@,
+                              memory_order = memory_order::seq_cst) const noexcept;
+    constexpr @\placeholdernc{floating-point-type}@ fetch_fminimum_num(@\placeholdernc{floating-point-type}@,
+                              memory_order = memory_order::seq_cst) const noexcept;
+
     constexpr value_type operator+=(value_type) const noexcept;
     constexpr value_type operator-=(value_type) const noexcept;
 
@@ -3792,10 +3805,24 @@
 \pnum
 The following operations perform arithmetic computations.
 The correspondence among key, operator, and computation is specified
-in \tref{atomic.types.int.comp}.
+in \tref{atomic.types.int.comp},
+except for the keys
+\tcode{max},
+\tcode{min},
+\tcode{fmaximum},
+\tcode{fminimum},
+\tcode{fmaximum_num}, and
+\tcode{fminimum_num},
+which are specified below.
 
 \indexlibrarymember{fetch_add}{atomic_ref<\placeholder{floating-point-type}>}%
 \indexlibrarymember{fetch_sub}{atomic_ref<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fmaximum}{atomic_ref<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fminimum}{atomic_ref<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fmaximum_num}{atomic_ref<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fminimum_num}{atomic_ref<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_max}{atomic_ref<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_min}{atomic_ref<\placeholder{floating-point-type}>}%
 \begin{itemdecl}
 constexpr value_type fetch_@\placeholdernc{key}@(value_type operand,
                           memory_order order = memory_order::seq_cst) const noexcept;
@@ -3830,6 +3857,41 @@
 The floating-point environment\iref{cfenv}
 for atomic arithmetic operations on \tcode{\placeholder{floating-\newline point-type}}
 may be different than the calling thread's floating-point environment.
+
+\pnum
+\begin{itemize}
+\item
+For \tcode{fetch_fmaximum} and \tcode{fetch_fminimum},
+the maximum and minimum computation is performed
+as if by \tcode{fmaximum} and \tcode{fminimum}, respectively,
+with \tcode{*ptr} and the first parameter as the arguments.
+\item
+For \tcode{fetch_fmaximum_num} and \tcode{fetch_fminimum_num},
+the maximum and minimum computation is performed
+as if by \tcode{fmaximum_num} and \tcode{fminimum_num}, respectively,
+with \tcode{*ptr} and the first parameter as the arguments.
+\item
+For \tcode{fetch_max} and \tcode{fetch_min},
+the maximum and minimum computation is performed
+as if by \tcode{fmaximum_num} and \tcode{fminimum_num}, respectively,
+with \tcode{*ptr} and the first parameter as the arguments, except that:
+\begin{itemize}
+\item
+If both arguments are NaN, an unspecified NaN value is stored at \tcode{*ptr}.
+\item
+If exactly one argument is a NaN,
+either the other argument or an unspecified NaN value is stored at \tcode{*ptr};
+it is unspecified which.
+\item
+If the arguments are differently signed zeros,
+which of these values is stored at \tcode{*ptr} is unspecified.
+\end{itemize}
+\end{itemize}
+
+\pnum
+\recommended
+The implementation of \tcode{fetch_max} and \tcode{fetch_min}
+should treat negative zero as smaller than positive zero.
 \end{itemdescr}
 
 \indexlibrarymember{operator+=}{atomic_ref<\placeholder{floating-point-type}>}%
@@ -4965,6 +5027,30 @@
                                   memory_order = memory_order::seq_cst) volatile noexcept;
     constexpr @\placeholdernc{floating-point-type}@ fetch_sub(@\placeholdernc{floating-point-type}@,
                                   memory_order = memory_order::seq_cst) noexcept;
+  @\placeholdernc{floating-point-type}@ fetch_max(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) volatile noexcept;
+  constexpr @\placeholdernc{floating-point-type}@ fetch_max(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) noexcept;
+  @\placeholdernc{floating-point-type}@ fetch_min(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) volatile noexcept;
+  constexpr @\placeholdernc{floating-poin-type}@t fetch_min(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) noexcept;
+  @\placeholdernc{floating-point-type}@ fetch_fmaximum(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) volatile noexcept;
+  constexpr @\placeholdernc{floating-point-type}@ fetch_fmaximum(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) noexcept;
+  @\placeholdernc{floating-point-type}@ fetch_fminimum(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) volatile noexcept;
+  constexpr @\placeholdernc{floating-point-type}@ fetch_fminimum(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) noexcept;
+  @\placeholdernc{floating-point-type}@ fetch_fmaximum_num(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) volatile noexcept;
+  constexpr @\placeholdernc{floating-point-type}@ fetch_fmaximum_num(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) noexcept;
+  @\placeholdernc{floating-point-type}@ fetch_fminimum_num(@\placeholdernc{floating-point-type}@,
+                                  memory_order = memory_order::seq_cst) volatile noexcept;
+  constexpr @\placeholdernc{floating-point-type}@ fetch_fminimum_num(f@\placeholdernc{loating-point-type}@,
+                                  memory_order = memory_order::seq_cst) noexcept;
 
     @\placeholdernc{floating-point-type}@ operator+=(@\placeholder{floating-point-type}@) volatile noexcept;
     constexpr @\placeholdernc{floating-point-type}@ operator+=(@\placeholder{floating-point-type}@) noexcept;
@@ -4994,14 +5080,28 @@
 \pnum
 The following operations perform arithmetic addition and subtraction computations.
 The correspondence among key, operator, and computation is specified
-in \tref{atomic.types.int.comp}.
+in \tref{atomic.types.int.comp},
+except for the keys
+\tcode{max},
+\tcode{min},
+\tcode{fmaximum},
+\tcode{fminimum},
+\tcode{fmaximum_num}, and
+\tcode{fminimum_num},
+which are specified below.
 
 \indexlibraryglobal{atomic_fetch_add}%
 \indexlibraryglobal{atomic_fetch_sub}%
 \indexlibraryglobal{atomic_fetch_add_explicit}%
 \indexlibraryglobal{atomic_fetch_sub_explicit}%
 \indexlibrarymember{fetch_add}{atomic<\placeholder{floating-point-type}>}%
 \indexlibrarymember{fetch_sub}{atomic<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fmaximum}{atomic<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fminimum}{atomic<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fmaximum_num}{atomic<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_fminimum_num}{atomic<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_max}{atomic<\placeholder{floating-point-type}>}%
+\indexlibrarymember{fetch_min}{atomic<\placeholder{floating-point-type}>}%
 \begin{itemdecl}
 T fetch_@\placeholdernc{key}@(T operand, memory_order order = memory_order::seq_cst) volatile noexcept;
 constexpr T fetch_@\placeholdernc{key}@(T operand, memory_order order = memory_order::seq_cst) noexcept;
@@ -5035,6 +5135,45 @@
 The floating-point environment\iref{cfenv} for atomic arithmetic operations
 on \tcode{\placeholder{floating-point-type}} may be different than the
 calling thread's floating-point environment.
+
+\pnum
+\begin{itemize}
+\item
+For \tcode{fetch_fmaximum} and \tcode{fetch_fminimum},
+the maximum and minimum computation is performed
+as if by \tcode{fmaximum} and \tcode{fminimum}, respectively,
+with the value pointed to by \tcode{this} and the first parameter
+as the arguments.
+\item
+For \tcode{fetch_fmaximum_num} and \tcode{fetch_fminimum_num},
+the maximum and minimum computation is performed
+as if by \tcode{fmaximum_num} and \tcode{fminimum_num}, respectively,
+with the value pointed to by \tcode{this} and the first parameter
+as the arguments.
+\item
+For \tcode{fetch_max} and \tcode{fetch_min},
+the maximum and minimum computation is performed
+as if by \tcode{fmaximum_num} and \tcode{fminimum_num}, respectively,
+with the value pointed to by \tcode{this} and the first parameter
+as the arguments, except that:
+\begin{itemize}
+\item
+If both arguments are NaN,
+an unspecified NaN value replaces the value pointed to by \tcode{this}.
+\item
+If exactly one argument is a NaN,
+either the other argument or an unspecified NaN value
+replaces the value pointed to by \tcode{this}; it is unspecified which.
+\item
+If the arguments are differently signed zeros,
+which of these values replaces the value pointed to by this is unspecified.
+\end{itemize}
+\end{itemize}
+
+\pnum
+\recommended
+The implementation of \tcode{fetch_max} and \tcode{fetch_min}
+should treat negative zero as smaller than positive zero.
 \end{itemdescr}
 
 \indexlibrarymember{operator+=}{atomic<T*>}%