25 lines
889 B
Zig
25 lines
889 B
Zig
const symbol = @import("../compiler_rt.zig").symbol;
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const testing = @import("std").testing;
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comptime {
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symbol(&__subvdi3, "__subvdi3");
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}
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pub fn __subvdi3(a: i64, b: i64) callconv(.c) i64 {
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const sum = a -% b;
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// Overflow occurred iff the operands have opposite signs, and the sign of the
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// sum is the opposite of the lhs sign.
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if (((a ^ b) & (sum ^ a)) < 0) @panic("compiler-rt: integer overflow");
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return sum;
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}
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test "subvdi3" {
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// min i64 = -9223372036854775808
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// max i64 = 9223372036854775807
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// TODO write panic handler for testing panics
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// try test__subvdi3(-9223372036854775808, -1, -1); // panic
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// try test__addvdi3(9223372036854775807, 1, 1); // panic
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try testing.expectEqual(-9223372036854775808, __subvdi3(-9223372036854775807, 1));
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try testing.expectEqual(9223372036854775807, __subvdi3(9223372036854775806, -1));
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}
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