The indices proc simply creates a vector where each lane contains its
own lane index. This can be useful for use in generating masks for loads
and stores at the beginning/end of slices, among other things.
The new reduce_add/reduce_mul procs perform the corresponding arithmetic
reduction, in different orders than just "in sequential order". These
alternative orders can often be faster to calculate, as they can offer
better SIMD hardware utilization.
Two different orders are added for these: pair-wise (operating on
adjacent pairs of elements) or split-wise (operating element-wise on the
two halves of the vector).
This doesn't actually cover the *fastest* way for arbitrarily-sized
vectors. That would be an ordered reduction across the native vector
width, then reducing the resulting vector to a scalar in an appropriate
parallel fashion. I'd created an implementation of that, but it required
multiple procs and a fair bit more trickery than I was comfortable with
submitting to `core`, so it's not included yet. Maybe in the future.
The purposes of this attribute is to let procedures opt-out of being
instrumented with asan. Typically an allocator that includes 'in-band'
meta-data will be accessing poisoned values (such as tlsf).
Making asan work with these allocators becomes very challenging so
just being to ignore asan within specific allocator procedures
makes it easier to reason and removes the need to temporarily
poison and unpoison allocator data.
It's a bit of a band aid fix because the field will get the type of the
alias, not the base type, but that was already the case before #5045 so
it's forward progression.
Closes#5092Fixes#5061
The initial allocation for the slice is limited to prevent untrusted
data from forcing a huge allocation, but then the dynamic array was
created with a capacity of the unlimited length, rather than the actual
capacity of the allocation. This was causing a buffer overrun.
This can be important if matrices or SIMD vectors are being used in
global or static variables, as otherwise it may result in crashes due to
aligned instructions accessing misaligned variables.
allocators
This adds various bindings to the asan runtime which can be used
to poison/unpoison memory handed out by various allocators. This
means we can catch use after free memory bugs when using operations
such as free_all during runtime.
Asan poisoning are added for the follow allocators in mem:
Arena (including temporary arenas)
Scratch
Stack
Small_Stack
Additionally a bug in the stack allocator was fixed to disallow freeing
in the middle of the stack (caught by the asan!).
I plan on adding support for all the allocators in core. This is just
a good starting point and were some of the easiest ones to implement
asan for.
Barinzaya
Jeroen van Rijn
gingerBill
jason
Lucas Perlind
Rohan Jadav
Laytan
Jamie Dennis
Michael Lee
gingerBill
Ely Alon