add the SwiftDtoa algorithm

Author: jaja360

benchmarks/CMakeLists.txt

@@ -77,4 +77,5 @@ endif()
 target_link_libraries(benchmark PUBLIC dragonbox::dragonbox_to_chars)
 target_link_libraries(benchmark PUBLIC dragon_schubfach_lib)
 target_link_libraries(benchmark PUBLIC dragon4_lib)
+target_link_libraries(benchmark PUBLIC swift_lib)
 target_include_directories(benchmark PUBLIC ${grisu-exact_SOURCE_DIR})

benchmarks/algorithms.h

@@ -32,12 +32,14 @@
 #include "ryu/ryu.h"
 #include "schubfach_32.h"
 #include "schubfach_64.h"
+#include "swift/Runtime/SwiftDtoa.h"
 #if (__SIZEOF_INT128__ == 16) && (defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER))
 #include "yy_double.h"
 #define YY_DOUBLE_SUPPORTED 1
 #else
 #define YY_DOUBLE_SUPPORTED 0
 #endif
+
 namespace Benchmarks {
 
 enum Algorithm {
@@ -57,7 +59,8 @@ enum Algorithm {
   ABSEIL = 13,
   STD_TO_CHARS = 14,
   GRISU3 = 15,
-  YY_DOUBLE = 16,
+  SWIFT_DTOA = 16,
+  YY_DOUBLE = 17,
   COUNT // Keep last
 };
 
@@ -230,6 +233,14 @@ int double_conversion(T d, std::span<char>& buffer) {
   return strlen(builder.Finalize());
 }
 
+template<arithmetic_float T>
+int swiftDtoa(T d, std::span<char>& buffer) {
+  if constexpr (std::is_same_v<T, float>)
+    return swift_dtoa_optimal_float(d, buffer.data(), buffer.size());
+  else
+    return swift_dtoa_optimal_double(d, buffer.data(), buffer.size());
+}
+
 template<arithmetic_float T>
 int yy_double(T d, std::span<char>& buffer) {
 #if YY_DOUBLE_SUPPORTED

benchmarks/benchmark.cpp

@@ -197,6 +197,7 @@ int main(int argc, char **argv) {
       args[Benchmarks::ABSEIL]            = { "abseil"            , Benchmarks::abseil<T>            , ABSEIL_SUPPORTED };
       args[Benchmarks::STD_TO_CHARS]      = { "std::to_chars"     , Benchmarks::std_to_chars<T>      , TO_CHARS_SUPPORTED };
       args[Benchmarks::GRISU3]            = { "grisu3"            , Benchmarks::grisu3<T>            , true };
+      args[Benchmarks::SWIFT_DTOA]        = { "SwiftDtoa"         , Benchmarks::swiftDtoa<T>         , true };
       args[Benchmarks::YY_DOUBLE]         = { "yy_double"         , Benchmarks::yy_double<T>         , YY_DOUBLE_SUPPORTED };
       return args;
     };

dependencies/CMakeLists.txt

@@ -97,11 +97,31 @@ add_library(dragon4_lib STATIC
 if(MATH_LIBRARY)
     target_link_libraries(dragon4_lib PUBLIC ${MATH_LIBRARY})
 endif()
-
 target_include_directories(dragon4_lib PUBLIC
     ${dragon4_SOURCE_DIR}
 )
 
+FetchContent_Declare(
+        swift
+        GIT_REPOSITORY https://github.com/swiftlang/swift.git
+        GIT_TAG 6a862d2eb7128ff1f317b07e8ad1a6da939775f3
+        GIT_SHALLOW TRUE
+)
+FetchContent_GetProperties(swift)
+if(NOT swift)
+  FetchContent_Populate(swift)  # Downloads code to ${dragon4_SOURCE_DIR}
+endif()
+set(swift_SOURCE_DIR ${swift_SOURCE_DIR} PARENT_SCOPE)
+add_library(swift_lib STATIC
+    ${swift_SOURCE_DIR}/stdlib/public/runtime/SwiftDtoa.cpp
+)
+if(MATH_LIBRARY)
+    target_link_libraries(swift_lib PUBLIC ${MATH_LIBRARY})
+endif()
+target_include_directories(swift_lib PUBLIC
+    ${swift_SOURCE_DIR}/include
+)
+
 FetchContent_Declare(
         drachennest # for schubfach
         GIT_REPOSITORY https://github.com/abolz/Drachennest.git