Progress:
- On holiday all week, at ACCU conference. I've put some highlights at
the end of the message.
- Did some more investigation into TCWG-466 ADRL support in integrated
assembler during breaks.
-- Not looking good, to do this properly bumps up against a lot of
design decisions and restrictions made by the LLVM assembler (designed
as compiler target, not to be user friendly).
-- There are ways it could be implemented with restrictions, but it is
debateable whether it is worth doing at all.
-- On the plus side I've got a much better idea of how the assembler
works and what restrictions exist on each stage of the journey from a
line in the .s file to emission in the object. Will add some comments
to the LDR r0, =expr TCWG as well.
-- On the negative side the :upper16: and :lower16: operators for MOVT
and MOVW don't look to be correct in the presence of addends. Will
need to investigate further to see what the scope of the problem is.
Plan:
- Dump results of TCWG-466 investigation into Jira.
- Take a look at and post a comment on Adhemerval's revised TLS patch,
even if it is just looks fine in the hope of pushing it forward a bit
more.
- Catch up with Renato's scripts and documents for LLVM sub-group.
- Work out what to do with TCWG-466, if the answer is put it down,
find something else to look at.
ACCU Highlights/Report:
Tough stuff in modern C++
A deep dive into some of the newer areas of C++ such as:
- rvalue references and forwarding (universal) references
- How to use SFINAE (mostly std::enable_if) to select algorithms
optimised for particular template instantiations
- Variadic templates. Including all sorts of strange ways to (ab)use
expansion of parameter packs.
C++ WG21 SG14 Gaming and low-latency study group
- A new study group aiming to represent the gaming (primarily), but
also embedded and high frequency trading concerns.
- Motto seemed to be make sure "Don't pay for what you don't use" is enforced.
Most interested in:
-- No exceptions configurations
-- No RTTI
-- More performance out of the STL (see EA STL
https://github.com/electronicarts/EASTL)
-- Add ring buffers and support for unitialised memory, fixed point
numbers, flat-map, standardised simd vector types
Using sentinels
- An example of how using two sentinels in an implementation of
std::partion speeds up the algorithm by saving comparisons. Can speed
up quicksort by a few percent
Constexpr in C++14
- Example showing how you could build a string to enum map, operating
entirely at compile time, and its subsequent negative effects on
compile time!
Concepts Lite
- Concepts missed the C++17 standard, this presentation went into the
current Technical Standard (optional) and how concepts would likely be
implemented in C++(20?)
- Not surprising to see that concepts still missed C++17 as there is
only one implementation and one non-trivial use case (ranges) and
there are still unresolved questions to be answered.
Introduction to Julia
- Really a comparison of Julia to the author's favoured language of common lisp.
- Was impressed at how "lispy" Julia was whilst retaining high performance.
- Liked the mathematical syntax
- Didn't like the python like parts that seemed to be added to try and
get people to migrate from python, but were non "lispy".