1 files changed, 22 insertions, 0 deletions
diff --git a/lib/std/special/compiler_rt/floatdidf.zig b/lib/std/special/compiler_rt/floatdidf.zig
new file mode 100644
index 0000000000..1610136413
--- /dev/null
+++ b/lib/std/special/compiler_rt/floatdidf.zig
@@ -0,0 +1,22 @@
+const builtin = @import("builtin");
+const std = @import("std");
+
+const twop52: f64 = 0x1.0p52;
+const twop32: f64 = 0x1.0p32;
+
+pub extern fn __floatdidf(a: i64) f64 {
+    @setRuntimeSafety(builtin.is_test);
+
+    if (a == 0) return 0;
+
+    var low = @bitCast(i64, twop52);
+    const high = @intToFloat(f64, @truncate(i32, a >> 32)) * twop32;
+
+    low |= @bitCast(i64, a & 0xFFFFFFFF);
+
+    return (high - twop52) + @bitCast(f64, low);
+}
+
+test "import floatdidf" {
+    _ = @import("floatdidf_test.zig");
+}