mirror of
https://github.com/ziglang/zig.git
synced 2024-12-03 18:38:45 +00:00
30f2bb8464
When we're compiling compiler_rt for any WebAssembly target, we do not want to expose all the compiler-rt functions to the host runtime. By setting the visibility of all exports to `hidden`, we allow the linker to resolve the symbols during linktime, while not expose the functions to the host runtime. This also means the linker can properly garbage collect any compiler-rt function that does not get resolved. The symbol visibility for all target remains the same as before: `default`.
48 lines
1.7 KiB
Zig
48 lines
1.7 KiB
Zig
//! subo - subtract overflow
|
|
//! * return a-%b.
|
|
//! * return if a-b overflows => 1 else => 0
|
|
//! - suboXi4_generic as default
|
|
|
|
const std = @import("std");
|
|
const builtin = @import("builtin");
|
|
const common = @import("common.zig");
|
|
|
|
pub const panic = common.panic;
|
|
|
|
comptime {
|
|
@export(__subosi4, .{ .name = "__subosi4", .linkage = common.linkage, .visibility = common.visibility });
|
|
@export(__subodi4, .{ .name = "__subodi4", .linkage = common.linkage, .visibility = common.visibility });
|
|
@export(__suboti4, .{ .name = "__suboti4", .linkage = common.linkage, .visibility = common.visibility });
|
|
}
|
|
|
|
pub fn __subosi4(a: i32, b: i32, overflow: *c_int) callconv(.C) i32 {
|
|
return suboXi4_generic(i32, a, b, overflow);
|
|
}
|
|
pub fn __subodi4(a: i64, b: i64, overflow: *c_int) callconv(.C) i64 {
|
|
return suboXi4_generic(i64, a, b, overflow);
|
|
}
|
|
pub fn __suboti4(a: i128, b: i128, overflow: *c_int) callconv(.C) i128 {
|
|
return suboXi4_generic(i128, a, b, overflow);
|
|
}
|
|
|
|
inline fn suboXi4_generic(comptime ST: type, a: ST, b: ST, overflow: *c_int) ST {
|
|
overflow.* = 0;
|
|
var sum: ST = a -% b;
|
|
// Hackers Delight: section Overflow Detection, subsection Signed Add/Subtract
|
|
// Let sum = a -% b == a - b - carry == wraparound subtraction.
|
|
// Overflow in a-b-carry occurs, iff a and b have opposite signs
|
|
// and the sign of a-b-carry is opposite of a (or equivalently same as b).
|
|
// Faster routine: res = (a ^ b) & (sum ^ a)
|
|
// Slower routine: res = (sum^a) & ~(sum^b)
|
|
// Overflow occured, iff (res < 0)
|
|
if (((a ^ b) & (sum ^ a)) < 0)
|
|
overflow.* = 1;
|
|
return sum;
|
|
}
|
|
|
|
test {
|
|
_ = @import("subosi4_test.zig");
|
|
_ = @import("subodi4_test.zig");
|
|
_ = @import("suboti4_test.zig");
|
|
}
|