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negv.zig (1303B) - Raw

      1 //! negv - negate oVerflow
      2 //! * @panic, if result can not be represented
      3 //! - negvXi4_generic for unoptimized version
      4 const std = @import("std");
      5 const builtin = @import("builtin");
      6 const common = @import("common.zig");
      7 
      8 pub const panic = common.panic;
      9 
     10 comptime {
     11     @export(&__negvsi2, .{ .name = "__negvsi2", .linkage = common.linkage, .visibility = common.visibility });
     12     @export(&__negvdi2, .{ .name = "__negvdi2", .linkage = common.linkage, .visibility = common.visibility });
     13     @export(&__negvti2, .{ .name = "__negvti2", .linkage = common.linkage, .visibility = common.visibility });
     14 }
     15 
     16 pub fn __negvsi2(a: i32) callconv(.c) i32 {
     17     return negvXi(i32, a);
     18 }
     19 
     20 pub fn __negvdi2(a: i64) callconv(.c) i64 {
     21     return negvXi(i64, a);
     22 }
     23 
     24 pub fn __negvti2(a: i128) callconv(.c) i128 {
     25     return negvXi(i128, a);
     26 }
     27 
     28 inline fn negvXi(comptime ST: type, a: ST) ST {
     29     const UT = switch (ST) {
     30         i32 => u32,
     31         i64 => u64,
     32         i128 => u128,
     33         else => unreachable,
     34     };
     35     const N: UT = @bitSizeOf(ST);
     36     const min: ST = @as(ST, @bitCast((@as(UT, 1) << (N - 1))));
     37     if (a == min)
     38         @panic("compiler_rt negv: overflow");
     39     return -a;
     40 }
     41 
     42 test {
     43     _ = @import("negvsi2_test.zig");
     44     _ = @import("negvdi2_test.zig");
     45     _ = @import("negvti2_test.zig");
     46 }