63 lines
1.8 KiB
Zig
63 lines
1.8 KiB
Zig
const builtin = @import("builtin");
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const compiler_rt = @import("../compiler_rt.zig");
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// Ported from git@github.com:llvm-project/llvm-project-20170507.git
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// ae684fad6d34858c014c94da69c15e7774a633c3
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// 2018-08-13
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pub fn __multi3(a: i128, b: i128) callconv(.C) i128 {
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@setRuntimeSafety(builtin.is_test);
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const x = twords{ .all = a };
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const y = twords{ .all = b };
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var r = twords{ .all = __mulddi3(x.s.low, y.s.low) };
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r.s.high +%= x.s.high *% y.s.low +% x.s.low *% y.s.high;
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return r.all;
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}
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const v128 = @Vector(2, u64);
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pub fn __multi3_windows_x86_64(a: v128, b: v128) callconv(.C) v128 {
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return @bitCast(v128, @call(.{ .modifier = .always_inline }, __multi3, .{
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@bitCast(i128, a),
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@bitCast(i128, b),
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}));
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}
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fn __mulddi3(a: u64, b: u64) i128 {
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const bits_in_dword_2 = (@sizeOf(i64) * 8) / 2;
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const lower_mask = ~@as(u64, 0) >> bits_in_dword_2;
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var r: twords = undefined;
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r.s.low = (a & lower_mask) *% (b & lower_mask);
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var t: u64 = r.s.low >> bits_in_dword_2;
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r.s.low &= lower_mask;
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t +%= (a >> bits_in_dword_2) *% (b & lower_mask);
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r.s.low +%= (t & lower_mask) << bits_in_dword_2;
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r.s.high = t >> bits_in_dword_2;
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t = r.s.low >> bits_in_dword_2;
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r.s.low &= lower_mask;
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t +%= (b >> bits_in_dword_2) *% (a & lower_mask);
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r.s.low +%= (t & lower_mask) << bits_in_dword_2;
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r.s.high +%= t >> bits_in_dword_2;
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r.s.high +%= (a >> bits_in_dword_2) *% (b >> bits_in_dword_2);
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return r.all;
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}
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const twords = extern union {
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all: i128,
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s: S,
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const S = if (builtin.endian == .Little)
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struct {
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low: u64,
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high: u64,
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}
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else
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struct {
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high: u64,
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low: u64,
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};
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};
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test "import multi3" {
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_ = @import("multi3_test.zig");
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}
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