Merge pull request #3315 from ziglang/mv-std-lib

Move std/ to lib/std/

1 files changed, 61 insertions, 0 deletions

diff --git a/lib/std/special/compiler_rt/floatuntisf.zig b/lib/std/special/compiler_rt/floatuntisf.zig
new file mode 100644
index 0000000000..1b42b267d9
--- /dev/null
+++ b/lib/std/special/compiler_rt/floatuntisf.zig
@@ -0,0 +1,61 @@
+const builtin = @import("builtin");
+const is_test = builtin.is_test;
+const std = @import("std");
+const maxInt = std.math.maxInt;
+
+const FLT_MANT_DIG = 24;
+
+pub extern fn __floatuntisf(arg: u128) f32 {
+    @setRuntimeSafety(is_test);
+
+    if (arg == 0)
+        return 0.0;
+
+    var a = arg;
+    const N: u32 = @sizeOf(u128) * 8;
+    const sd = @bitCast(i32, N - @clz(u128, a)); // number of significant digits
+    var e: i32 = sd - 1; // exponent
+    if (sd > FLT_MANT_DIG) {
+        //  start:  0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
+        //  finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
+        //                                                12345678901234567890123456
+        //  1 = msb 1 bit
+        //  P = bit FLT_MANT_DIG-1 bits to the right of 1
+        //  Q = bit FLT_MANT_DIG bits to the right of 1
+        //  R = "or" of all bits to the right of Q
+        switch (sd) {
+            FLT_MANT_DIG + 1 => {
+                a <<= 1;
+            },
+            FLT_MANT_DIG + 2 => {},
+            else => {
+                const shift_amt = @bitCast(i32, N + (FLT_MANT_DIG + 2)) - sd;
+                const shift_amt_u7 = @intCast(u7, shift_amt);
+                a = (a >> @intCast(u7, sd - (FLT_MANT_DIG + 2))) |
+                    @boolToInt((a & (u128(maxInt(u128)) >> shift_amt_u7)) != 0);
+            },
+        }
+        // finish
+        a |= @boolToInt((a & 4) != 0); // Or P into R
+        a += 1; // round - this step may add a significant bit
+        a >>= 2; // dump Q and R
+        // a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits
+        if ((a & (u128(1) << FLT_MANT_DIG)) != 0) {
+            a >>= 1;
+            e += 1;
+        }
+        // a is now rounded to FLT_MANT_DIG bits
+    } else {
+        a <<= @intCast(u7, FLT_MANT_DIG - sd);
+        // a is now rounded to FLT_MANT_DIG bits
+    }
+
+    const high = @bitCast(u32, (e + 127) << 23); // exponent
+    const low = @truncate(u32, a) & 0x007fffff; // mantissa
+
+    return @bitCast(f32, high | low);
+}
+
+test "import floatuntisf" {
+    _ = @import("floatuntisf_test.zig");
+}