Merge branch 'master' into zen_stdlib

1 files changed, 29 insertions, 0 deletions

diff --git a/std/special/compiler_rt/floatunsitf.zig b/std/special/compiler_rt/floatunsitf.zig
new file mode 100644
index 0000000000..19a5918bd0
--- /dev/null
+++ b/std/special/compiler_rt/floatunsitf.zig
@@ -0,0 +1,29 @@
+const builtin = @import("builtin");
+const is_test = builtin.is_test;
+const std = @import("std");
+
+pub extern fn __floatunsitf(a: u64) f128 {
+    @setRuntimeSafety(is_test);
+
+    if (a == 0) {
+        return 0;
+    }
+
+    const mantissa_bits = std.math.floatMantissaBits(f128);
+    const exponent_bits = std.math.floatExponentBits(f128);
+    const exponent_bias = (1 << (exponent_bits - 1)) - 1;
+    const implicit_bit = 1 << mantissa_bits;
+
+    const exp = (u64.bit_count - 1) - @clz(a);
+    const shift = mantissa_bits - @intCast(u7, exp);
+
+    // TODO(#1148): @bitCast alignment error
+    var result align(16) = (@intCast(u128, a) << shift) ^ implicit_bit;
+    result += (@intCast(u128, exp) + exponent_bias) << mantissa_bits;
+
+    return @bitCast(f128, result);
+}
+
+test "import floatunsitf" {
+    _ = @import("floatunsitf_test.zig");
+}