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//! Ported from git@github.com:llvm-project/llvm-project-20170507.git
//! ae684fad6d34858c014c94da69c15e7774a633c3
//! 2018-08-13
const std = @import("std");
const builtin = @import("builtin");
const native_endian = builtin.cpu.arch.endian();
const common = @import("common.zig");
pub const panic = common.panic;
comptime {
if (common.want_windows_v2u64_abi) {
@export(__multi3_windows_x86_64, .{ .name = "__multi3", .linkage = common.linkage });
} else {
@export(__multi3, .{ .name = "__multi3", .linkage = common.linkage });
}
}
pub fn __multi3(a: i128, b: i128) callconv(.C) i128 {
return mul(a, b);
}
const v2u64 = @Vector(2, u64);
fn __multi3_windows_x86_64(a: v2u64, b: v2u64) callconv(.C) v2u64 {
return @bitCast(v2u64, mul(@bitCast(i128, a), @bitCast(i128, b)));
}
inline fn mul(a: i128, b: i128) i128 {
const x = twords{ .all = a };
const y = twords{ .all = b };
var r = twords{ .all = mulddi3(x.s.low, y.s.low) };
r.s.high +%= x.s.high *% y.s.low +% x.s.low *% y.s.high;
return r.all;
}
fn mulddi3(a: u64, b: u64) i128 {
const bits_in_dword_2 = (@sizeOf(i64) * 8) / 2;
const lower_mask = ~@as(u64, 0) >> bits_in_dword_2;
var r: twords = undefined;
r.s.low = (a & lower_mask) *% (b & lower_mask);
var t: u64 = r.s.low >> bits_in_dword_2;
r.s.low &= lower_mask;
t +%= (a >> bits_in_dword_2) *% (b & lower_mask);
r.s.low +%= (t & lower_mask) << bits_in_dword_2;
r.s.high = t >> bits_in_dword_2;
t = r.s.low >> bits_in_dword_2;
r.s.low &= lower_mask;
t +%= (b >> bits_in_dword_2) *% (a & lower_mask);
r.s.low +%= (t & lower_mask) << bits_in_dword_2;
r.s.high +%= t >> bits_in_dword_2;
r.s.high +%= (a >> bits_in_dword_2) *% (b >> bits_in_dword_2);
return r.all;
}
const twords = extern union {
all: i128,
s: S,
const S = if (native_endian == .Little)
extern struct {
low: u64,
high: u64,
}
else
extern struct {
high: u64,
low: u64,
};
};
test {
_ = @import("multi3_test.zig");
}
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