compiler-rt: Add __ashlti3

1 files changed, 41 insertions, 0 deletions

diff --git a/std/special/compiler_rt/ashlti3.zig b/std/special/compiler_rt/ashlti3.zig
new file mode 100644
index 0000000000..65b23f22e5
--- /dev/null
+++ b/std/special/compiler_rt/ashlti3.zig
@@ -0,0 +1,41 @@
+const builtin = @import("builtin");
+const compiler_rt = @import("../compiler_rt.zig");
+
+pub extern fn __ashlti3(a: i128, b: i32) i128 {
+    var input = twords{ .all = a };
+    var result: twords = undefined;
+
+    if (b > 63) {
+        // 64 <= b < 128
+        result.s.low = 0;
+        result.s.high = input.s.low << @intCast(u6, b - 64);
+    } else {
+        // 0 <= b < 64
+        if (b == 0) return a;
+        result.s.low = input.s.low << @intCast(u6, b);
+        result.s.high = input.s.low >> @intCast(u6, 64 - b);
+        result.s.high |= input.s.high << @intCast(u6, b);
+    }
+
+    return result.all;
+}
+
+const twords = extern union {
+    all: i128,
+    s: S,
+
+    const S = if (builtin.endian == builtin.Endian.Little)
+        struct {
+            low: u64,
+            high: u64,
+        }
+    else
+        struct {
+            high: u64,
+            low: u64,
+        };
+};
+
+test "import ashlti3" {
+    _ = @import("ashlti3_test.zig");
+}