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Fix normalization of right-shifted BigInt at CT

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The pointer value for the `digits` field was being treated as if it were
a limb.

Fixes #2225
This commit is contained in:
LemonBoy 2019-04-10 10:57:43 +02:00 committed by Andrew Kelley
parent e309ad884a
commit 8f5753ba9f
2 changed files with 17 additions and 2 deletions
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11
src/bigint.cpp
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@ -1410,12 +1410,19 @@ void bigint_shr(BigInt *dest, const BigInt *op1, const BigInt *op2) {
}
dest->digit_count = op1->digit_count - digit_shift_count;
dest->data.digits = allocate<uint64_t>(dest->digit_count);
uint64_t *digits;
if (dest->digit_count == 1) {
digits = &dest->data.digit;
} else {
digits = allocate<uint64_t>(dest->digit_count);
dest->data.digits = digits;
}
uint64_t carry = 0;
for (size_t op_digit_index = op1->digit_count - 1;;) {
uint64_t digit = op1_digits[op_digit_index];
size_t dest_digit_index = op_digit_index - digit_shift_count;
dest->data.digits[dest_digit_index] = carry | (digit >> leftover_shift_count);
digits[dest_digit_index] = carry | (digit >> leftover_shift_count);
carry = digit << (64 - leftover_shift_count);
if (dest_digit_index == 0) { break; }

8
test/stage1/behavior/bit_shifting.zig
View File

@ -86,3 +86,11 @@ fn testShardedTable(comptime Key: type, comptime mask_bit_count: comptime_int, c
expect(table.get(@intCast(Key, i)) == node);
}
}
// #2225
test "comptime shr of BigInt" {
comptime {
var n = 0xdeadbeef0000000000000000;
std.debug.assert(n >> 64 == 0xdeadbeef);
}
}