From e05fa5c1c3a2b11217cd2589c80978a66a01d84a Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Sat, 27 Jun 2020 14:58:30 +0100
Subject: [PATCH] CMake: Add builtins

---
 CMakeLists.txt           |  1 +
 cmake/FindBuiltins.cmake | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 cmake/FindBuiltins.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 34697e09b2..184ff3ab27 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -42,6 +42,7 @@ if (NOT WIN32)
     find_package(Fontconfig)
     find_package(ICU OPTIONAL_COMPONENTS i18n lx)
     find_package(XDG_basedir)
+    find_package(Builtins)
 endif (NOT WIN32)
 if (APPLE)
     find_package(Iconv)
diff --git a/cmake/FindBuiltins.cmake b/cmake/FindBuiltins.cmake
new file mode 100644
index 0000000000..c84292729b
--- /dev/null
+++ b/cmake/FindBuiltins.cmake
@@ -0,0 +1,34 @@
+include(CheckCXXSourceCompiles)
+
+check_cxx_source_compiles("
+    int main() {
+        return __builtin_popcountll(__builtin_popcountl(__builtin_popcount(__builtin_ctz(1))));
+    }"
+    BITMATH_BUILTINS_FOUND
+)
+
+if (BITMATH_BUILTINS_FOUND)
+    add_compile_options(
+        -DWITH_BITMATH_BUILTINS
+    )
+endif (BITMATH_BUILTINS_FOUND)
+
+check_cxx_source_compiles("
+#include <cstdint>
+int main() {
+    int64_t a = 0;
+    int64_t b = 0;
+    int64_t c = 0;
+    bool res1 = __builtin_add_overflow(a, b, &c);
+    bool res2 = __builtin_sub_overflow(a, b, &c);
+    bool res3 = __builtin_mul_overflow(a, b, &c);
+    return (res1 || res2 || res3) ? 1 : 0;
+}"
+    OVERFLOW_BUILTINS_FOUND
+)
+
+if (OVERFLOW_BUILTINS_FOUND)
+    add_compile_options(
+        -DWITH_OVERFLOW_BUILTINS
+    )
+endif (OVERFLOW_BUILTINS_FOUND)