compiler-rt: Add __mulodi4

3 files changed, 130 insertions, 0 deletions

diff --git a/std/special/compiler_rt.zig b/std/special/compiler_rt.zig
index d6af9535d7..76aebc24d7 100644
--- a/std/special/compiler_rt.zig
+++ b/std/special/compiler_rt.zig
@@ -221,6 +221,7 @@ comptime {
         @export("__umodti3", @import("compiler_rt/umodti3.zig").__umodti3, linkage);
     }
     @export("__muloti4", @import("compiler_rt/muloti4.zig").__muloti4, linkage);
+    @export("__mulodi4", @import("compiler_rt/mulodi4.zig").__mulodi4, linkage);
 }
 
 const std = @import("std");
diff --git a/std/special/compiler_rt/mulodi4.zig b/std/special/compiler_rt/mulodi4.zig
new file mode 100644
index 0000000000..82e9ef3253
--- /dev/null
+++ b/std/special/compiler_rt/mulodi4.zig
@@ -0,0 +1,44 @@
+const builtin = @import("builtin");
+const compiler_rt = @import("../compiler_rt.zig");
+const maxInt = std.math.maxInt;
+const minInt = std.math.minInt;
+
+pub extern fn __mulodi4(a: i64, b: i64, overflow: *c_int) i64 {
+    @setRuntimeSafety(builtin.is_test);
+
+    const min = @bitCast(i64, u64(1 << (i64.bit_count - 1)));
+    const max = ~min;
+
+    overflow.* = 0;
+    const result = a *% b;
+
+    // Edge cases
+    if (a == min) {
+        if (b != 0 and b != 1) overflow.* = 1;
+        return result;
+    }
+    if (b == min) {
+        if (a != 0 and a != 1) overflow.* = 1;
+        return result;
+    }
+
+    // Take absolute value of a and b via abs(x) = (x^(x >> 63)) - (x >> 63).
+    const abs_a = (a ^ (a >> 63)) -% (a >> 63);
+    const abs_b = (b ^ (b >> 63)) -% (b >> 63);
+
+    // Unitary magnitude, cannot have overflow
+    if (abs_a < 2 or abs_b < 2) return result;
+
+    // Compare the signs of the operands
+    if ((a ^ b) >> 63 != 0) {
+        if (abs_a > @divTrunc(max, abs_b)) overflow.* = 1;
+    } else {
+        if (abs_a > @divTrunc(min, -abs_b)) overflow.* = 1;
+    }
+
+    return result;
+}
+
+test "import mulodi4" {
+    _ = @import("mulodi4_test.zig");
+}
diff --git a/std/special/compiler_rt/mulodi4_test.zig b/std/special/compiler_rt/mulodi4_test.zig
new file mode 100644
index 0000000000..7575c77044
--- /dev/null
+++ b/std/special/compiler_rt/mulodi4_test.zig
@@ -0,0 +1,85 @@
+const __mulodi4 = @import("mulodi4.zig").__mulodi4;
+const testing = @import("std").testing;
+
+fn test__mulodi4(a: i64, b: i64, expected: i64, expected_overflow: c_int) void {
+    var overflow: c_int = undefined;
+    const x = __mulodi4(a, b, &overflow);
+    testing.expect(overflow == expected_overflow and (expected_overflow != 0 or x == expected));
+}
+
+test "mulodi4" {
+    test__mulodi4(0, 0, 0, 0);
+    test__mulodi4(0, 1, 0, 0);
+    test__mulodi4(1, 0, 0, 0);
+    test__mulodi4(0, 10, 0, 0);
+    test__mulodi4(10, 0, 0, 0);
+    test__mulodi4(0, 81985529216486895, 0, 0);
+    test__mulodi4(81985529216486895, 0, 0, 0);
+
+    test__mulodi4(0, -1, 0, 0);
+    test__mulodi4(-1, 0, 0, 0);
+    test__mulodi4(0, -10, 0, 0);
+    test__mulodi4(-10, 0, 0, 0);
+    test__mulodi4(0, -81985529216486895, 0, 0);
+    test__mulodi4(-81985529216486895, 0, 0, 0);
+
+    test__mulodi4(1, 1, 1, 0);
+    test__mulodi4(1, 10, 10, 0);
+    test__mulodi4(10, 1, 10, 0);
+    test__mulodi4(1, 81985529216486895, 81985529216486895, 0);
+    test__mulodi4(81985529216486895, 1, 81985529216486895, 0);
+
+    test__mulodi4(1, -1, -1, 0);
+    test__mulodi4(1, -10, -10, 0);
+    test__mulodi4(-10, 1, -10, 0);
+    test__mulodi4(1, -81985529216486895, -81985529216486895, 0);
+    test__mulodi4(-81985529216486895, 1, -81985529216486895, 0);
+
+    test__mulodi4(3037000499, 3037000499, 9223372030926249001, 0);
+    test__mulodi4(-3037000499, 3037000499, -9223372030926249001, 0);
+    test__mulodi4(3037000499, -3037000499, -9223372030926249001, 0);
+    test__mulodi4(-3037000499, -3037000499, 9223372030926249001, 0);
+
+    test__mulodi4(4398046511103, 2097152, 9223372036852678656, 0);
+    test__mulodi4(-4398046511103, 2097152, -9223372036852678656, 0);
+    test__mulodi4(4398046511103, -2097152, -9223372036852678656, 0);
+    test__mulodi4(-4398046511103, -2097152, 9223372036852678656, 0);
+
+    test__mulodi4(2097152, 4398046511103, 9223372036852678656, 0);
+    test__mulodi4(-2097152, 4398046511103, -9223372036852678656, 0);
+    test__mulodi4(2097152, -4398046511103, -9223372036852678656, 0);
+    test__mulodi4(-2097152, -4398046511103, 9223372036852678656, 0);
+
+    test__mulodi4(0x7FFFFFFFFFFFFFFF, -2, 2, 1);
+    test__mulodi4(-2, 0x7FFFFFFFFFFFFFFF, 2, 1);
+    test__mulodi4(0x7FFFFFFFFFFFFFFF, -1, @bitCast(i64, u64(0x8000000000000001)), 0);
+    test__mulodi4(-1, 0x7FFFFFFFFFFFFFFF, @bitCast(i64, u64(0x8000000000000001)), 0);
+    test__mulodi4(0x7FFFFFFFFFFFFFFF, 0, 0, 0);
+    test__mulodi4(0, 0x7FFFFFFFFFFFFFFF, 0, 0);
+    test__mulodi4(0x7FFFFFFFFFFFFFFF, 1, 0x7FFFFFFFFFFFFFFF, 0);
+    test__mulodi4(1, 0x7FFFFFFFFFFFFFFF, 0x7FFFFFFFFFFFFFFF, 0);
+    test__mulodi4(0x7FFFFFFFFFFFFFFF, 2, @bitCast(i64, u64(0x8000000000000001)), 1);
+    test__mulodi4(2, 0x7FFFFFFFFFFFFFFF, @bitCast(i64, u64(0x8000000000000001)), 1);
+
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000000)), -2, @bitCast(i64, u64(0x8000000000000000)), 1);
+    test__mulodi4(-2, @bitCast(i64, u64(0x8000000000000000)), @bitCast(i64, u64(0x8000000000000000)), 1);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000000)), -1, @bitCast(i64, u64(0x8000000000000000)), 1);
+    test__mulodi4(-1, @bitCast(i64, u64(0x8000000000000000)), @bitCast(i64, u64(0x8000000000000000)), 1);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000000)), 0, 0, 0);
+    test__mulodi4(0, @bitCast(i64, u64(0x8000000000000000)), 0, 0);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000000)), 1, @bitCast(i64, u64(0x8000000000000000)), 0);
+    test__mulodi4(1, @bitCast(i64, u64(0x8000000000000000)), @bitCast(i64, u64(0x8000000000000000)), 0);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000000)), 2, @bitCast(i64, u64(0x8000000000000000)), 1);
+    test__mulodi4(2, @bitCast(i64, u64(0x8000000000000000)), @bitCast(i64, u64(0x8000000000000000)), 1);
+
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000001)), -2, @bitCast(i64, u64(0x8000000000000001)), 1);
+    test__mulodi4(-2, @bitCast(i64, u64(0x8000000000000001)), @bitCast(i64, u64(0x8000000000000001)), 1);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000001)), -1, 0x7FFFFFFFFFFFFFFF, 0);
+    test__mulodi4(-1, @bitCast(i64, u64(0x8000000000000001)), 0x7FFFFFFFFFFFFFFF, 0);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000001)), 0, 0, 0);
+    test__mulodi4(0, @bitCast(i64, u64(0x8000000000000001)), 0, 0);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000001)), 1, @bitCast(i64, u64(0x8000000000000001)), 0);
+    test__mulodi4(1, @bitCast(i64, u64(0x8000000000000001)), @bitCast(i64, u64(0x8000000000000001)), 0);
+    test__mulodi4(@bitCast(i64, u64(0x8000000000000001)), 2, @bitCast(i64, u64(0x8000000000000000)), 1);
+    test__mulodi4(2, @bitCast(i64, u64(0x8000000000000001)), @bitCast(i64, u64(0x8000000000000000)), 1);
+}