If a big integer were to become negative zero, set the sign to instead
be positive. This prevents odd scenarios where users of signed big ints
would falsely think the result of some big int arithmetic is negative.
Removes the UnsignedBigInteger overloads of
SignedBigInteger::binary_{and,or,xor}(). They're now unused, and they
also didn't work when *this was negative.
We went through some trouble to make & and | work right. Reimplement ^
in terms of & and | to make ^ work right as well.
This is less fast than a direct implementation, but let's get things
working first.
Similar to the bitwise_and change, but we have to be careful to
sign-extend two's complement numbers only up to the highest set bit
in the positive number.
Bitwise and is defined in terms of two's complement, so some converting
needs to happen for SignedBigInteger's sign/magnitude representation to
work out.
UnsignedBigInteger::bitwise_not() is repurposed to convert all
high-order zero bits to ones up to a limit, for the two's complement
conversion to work.
Fixes test262/test/language/expressions/bitwise-and/bigint.js.
Bitwise operators are defined on two's complement, but SignedBitInteger
uses sign-magnitude. Correctly convert between the two.
Let LibJS delegate to SignedBitInteger for bitwise_not, like it does
for all other bitwise_ operations on bigints.
No behavior change (LibJS is now the only client of
SignedBitInteger::bitwise_not()).
In order to reduce our reliance on __builtin_{ffs, clz, ctz, popcount},
this commit removes all calls to these functions and replaces them with
the equivalent functions in AK/BuiltinWrappers.h.
This isn't a complete conversion to ErrorOr<void>, but a good chunk.
The end goal here is to propagate buffer allocation failures to the
caller, and allow the use of TRY() with formatting functions.
Currently, we get the following results
-1 - -2 = -1
-2 - -1 = 1
Correct would be:
-1 - -2 = 1
-2 - -1 = -1
This was already attempted to be fixed in 7ed8970, but that change was
incorrect. This directly translates to LibJS BigInts having the same
incorrect behavior - it even was tested.
We never really needed the 512 words in the first place, and this does
reduce the stack allocations in montgomery modular power from 32Kb to
a more manageable 2Kb :^)
Note that the 32 words size doesn't provide any performance benefits or
drawbacks compared to other values. All values seem to have equivalent
performances (the tested values were 1, 2, 4, ..., 512). But since the
previous value of 512 was definitely too big, let's reduce it for now!
This algorithm allows for much faster computations of modular powers
(around a 5x-10x speedup of the Crypto test). However, it is only valid
for odd modulo values, and therefore the old algorithm must be kept for
computations involving even modulo values.
Since the operations are already complicated and will become even more
so soon, let's split them into their own files. We can also integrate
the NumberTheory operations that would better fit there into this class
as well.
This commit doesn't change behaviors, but moves the allocation of some
variables into caller classes.
This is working fine for TLS because we have a big enough inline
capacity, but in theory we could have crashed at any time even with
our 512 words of inline capacity.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
If we don't limit the sizes of the intermediate results, they will grow
indefinitely, causing each iteration to take longer and longer (in both
memcpy time, and algorithm runtime).
While calculating the trimmed length is fairly expensive, it's a small
cost to pay for uniform iteration times.
This is basically just for consistency, it's quite strange to see
multiple AK container types next to each other, some with and some
without the namespace prefix - we're 'using AK::Foo;' a lot and should
leverage that. :^)
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
`length` is only the (trimmed) size of the word vector, so we have to
multiply it with the size of each element to ensure all bytes are
compared.
Fixes#5335.
