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absv.zig (671B) - Raw

      1 /// absv - absolute oVerflow
      2 /// * @panic if value can not be represented
      3 pub inline fn absv(comptime ST: type, a: ST) ST {
      4     const UT = switch (ST) {
      5         i32 => u32,
      6         i64 => u64,
      7         i128 => u128,
      8         else => unreachable,
      9     };
     10     // taken from  Bit Twiddling Hacks
     11     // compute the integer absolute value (abs) without branching
     12     var x: ST = a;
     13     const N: UT = @bitSizeOf(ST);
     14     const sign: ST = a >> N - 1;
     15     x +%= sign;
     16     x ^= sign;
     17     if (x < 0)
     18         @panic("compiler_rt absv: overflow");
     19     return x;
     20 }
     21 
     22 test {
     23     _ = @import("absvsi2_test.zig");
     24     _ = @import("absvdi2_test.zig");
     25     _ = @import("absvti2_test.zig");
     26 }