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60 lines
2 KiB
Zig
60 lines
2 KiB
Zig
//! a raised to integer power of b
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//! ported from https://github.com/llvm-mirror/compiler-rt/blob/release_80/lib/builtins/powisf2.c
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//! Multiplication order (left-to-right or right-to-left) does not matter for
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//! error propagation and this method is optimized for performance, not accuracy.
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const builtin = @import("builtin");
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const common = @import("common.zig");
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const std = @import("std");
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pub const panic = common.panic;
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comptime {
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@export(&__powihf2, .{ .name = "__powihf2", .linkage = common.linkage, .visibility = common.visibility });
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@export(&__powisf2, .{ .name = "__powisf2", .linkage = common.linkage, .visibility = common.visibility });
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@export(&__powidf2, .{ .name = "__powidf2", .linkage = common.linkage, .visibility = common.visibility });
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if (common.want_ppc_abi)
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@export(&__powitf2, .{ .name = "__powikf2", .linkage = common.linkage, .visibility = common.visibility });
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@export(&__powitf2, .{ .name = "__powitf2", .linkage = common.linkage, .visibility = common.visibility });
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@export(&__powixf2, .{ .name = "__powixf2", .linkage = common.linkage, .visibility = common.visibility });
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}
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inline fn powiXf2(comptime FT: type, a: FT, b: i32) FT {
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var x_a: FT = a;
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var x_b: i32 = b;
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const is_recip: bool = b < 0;
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var r: FT = 1.0;
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while (true) {
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if (@as(u32, @bitCast(x_b)) & @as(u32, 1) != 0) {
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r *= x_a;
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}
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x_b = @divTrunc(x_b, @as(i32, 2));
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if (x_b == 0) break;
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x_a *= x_a; // Multiplication of x_a propagates the error
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}
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return if (is_recip) 1 / r else r;
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}
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pub fn __powihf2(a: f16, b: i32) callconv(.c) f16 {
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return powiXf2(f16, a, b);
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}
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pub fn __powisf2(a: f32, b: i32) callconv(.c) f32 {
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return powiXf2(f32, a, b);
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}
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pub fn __powidf2(a: f64, b: i32) callconv(.c) f64 {
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return powiXf2(f64, a, b);
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}
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pub fn __powitf2(a: f128, b: i32) callconv(.c) f128 {
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return powiXf2(f128, a, b);
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}
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pub fn __powixf2(a: f80, b: i32) callconv(.c) f80 {
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return powiXf2(f80, a, b);
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}
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test {
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_ = @import("powiXf2_test.zig");
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}
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