51 lines
1.3 KiB
Zig
51 lines
1.3 KiB
Zig
// absv - absolute oVerflow
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// * @panic, if value can not be represented
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// - absvXi4_generic for unoptimized version
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const std = @import("std");
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const builtin = @import("builtin");
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const linkage: std.builtin.GlobalLinkage = if (builtin.is_test) .Internal else .Weak;
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pub const panic = @import("common.zig").panic;
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comptime {
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@export(__absvsi2, .{ .name = "__absvsi2", .linkage = linkage });
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@export(__absvdi2, .{ .name = "__absvdi2", .linkage = linkage });
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@export(__absvti2, .{ .name = "__absvti2", .linkage = linkage });
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}
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inline fn absvXi(comptime ST: type, a: ST) ST {
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const UT = switch (ST) {
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i32 => u32,
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i64 => u64,
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i128 => u128,
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else => unreachable,
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};
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// taken from Bit Twiddling Hacks
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// compute the integer absolute value (abs) without branching
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var x: ST = a;
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const N: UT = @bitSizeOf(ST);
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const sign: ST = a >> N - 1;
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x +%= sign;
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x ^= sign;
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if (x < 0)
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@panic("compiler_rt absv: overflow");
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return x;
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}
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pub fn __absvsi2(a: i32) callconv(.C) i32 {
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return absvXi(i32, a);
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}
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pub fn __absvdi2(a: i64) callconv(.C) i64 {
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return absvXi(i64, a);
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}
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pub fn __absvti2(a: i128) callconv(.C) i128 {
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return absvXi(i128, a);
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}
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test {
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_ = @import("absvsi2_test.zig");
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_ = @import("absvdi2_test.zig");
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_ = @import("absvti2_test.zig");
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}
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