There has been some ongoing confusion regarding when to use `llvm_unreachable`
which this patch attempts to address. Specifically, the confusion has been
around whether `llvm_unreachable` is intended to mark only unreachable code
paths that the compiler cannot determine itself or to mark a code path which is
unconditionally a bug to reach. Based on email and IRC discussions, it sounds
like "unconditional bug to reach" is the consensus.
There is prior art for this in the code base itself, and a recent
example of this here: c45f8d4989
This came up in discussion on this review where @maskray was going the
opposite direction:
https://reviews.llvm.org/D68772
Given that there is disagreement, we should make a choice and document
it.
Thanks to John McCall for the precise wording.
Reviewed By: MaskRay, rjmccall
Differential Revision: https://reviews.llvm.org/D74515
The existing wording leaves it unclear if C++ standard library data
structures should be preferred over custom LLVM ones, e.g., SmallVector,
even though common practice seems clear on the issue. This change makes
the wording more explicit and aligns it better with the code base.
Some motivating statistics:
```
ag SmallVector llvm/lib/ | wc
8846 40306 901421
ag 'std::vector' llvm/lib/ | wc
2123 8990 214482
ag SmallVector clang/lib/ | wc
3023 13824 281691
ag 'std::vector' clang/lib/ | wc
719 2914 72817
```
Differential Revision: https://reviews.llvm.org/D74340
This is a bit awkward in a handful of places where we didn't even have
an instruction and now we have to see if we can build one. But on the
whole, this seems like a win and at worst a reasonable cost for removing
`TerminatorInst`.
All of this is part of the removal of `TerminatorInst` from the
`Instruction` type hierarchy.
llvm-svn: 340701
Clarify that you should not introduce trailing whitespace when making a commit and that you should not remove trailing whitespace that's unrelated to code you are changing or are about to change. Then clarified the developer policy around what is considered an obvious whitespace commit.
llvm-svn: 339455
(I suppose these two pieces could be separated - but seemed related
enough)
As discussed on llvm-dev, this documents the general expectation of how
library layering should be handled. There are a few existing cases where
these constraints are not met, but as with most style guide things -
this is forward looking and provides guidance when cleaning up existing
code, it doesn't immediately require that all previous code be cleaned
up to match. (see: naming conventions, etc)
Differential Revision: https://reviews.llvm.org/D42771
llvm-svn: 324004
The CodingStandards section on avoiding the re-evaluation of end() hasn't been
updated since range-based for loops were adopted in the LLVM codebase. This
patch adds a very brief section that documents how range-based for loops
should be used wherever possible. It also moves example code in
CodingStandards to use range-based for loops and auto when appropriate.
Differential Revision: https://reviews.llvm.org/D37264
llvm-svn: 312236
Use text suggested by Justin Bogner in post-commit review of r311146
<http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20170814/479898.html>,
which makes it clear that report_fatal_error shouldn't be used when there is a
practicable alternative. Also make this clearer in CodingStandards.
llvm-svn: 311147
The current ProgrammersManual.rst document has a lot of well-written
documentation on error handling thanks to @lhames. It suggests errors can be
split cleanly into "programmatic" and "recoverable" errors. However, the
reality in current LLVM seems to be there are a number of cases where a
non-programmatic error is not easily recoverable. Therefore, add a note to
indicate the existence of report_fatal_error for these cases. I've also added
a reminder to CodingStandards.rst in the section on assertions, to indicate
that llvm_unreachable and assertions should not be relied upon to report
errors triggered by user input.
The ProgrammersManual is also silent on the use of LLVMContext::diagnose,
which is used in BPF+WebAssembly+AMDGPU to report some errors during
instruction selection. I don't address that in this patch, as it's not quite
clear how to fit in to the current error handling story
Differential Revision: https://reviews.llvm.org/D36826
llvm-svn: 311146
Summary:
The RFC proposal sent to increase the minimum required GCC version
to 4.8 received a lot of support. See the following thread:
http://lists.llvm.org/pipermail/llvm-dev/2016-October/105955.html,
This patch implements that by updating the docs. I believe the
references to libstdc++ 4.7 issues can be removed as well, please
let me know if that is not the case or if they should be updated
a different way.
Reviewers: rengolin
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D25683
llvm-svn: 284497
auto-brief format for doxygen comments. Most notable is switching to
that in the example doxygen comment. I've also tweaked the wording but
am happy to tweak it further if others have suggestions here.
Mostly doing this to capture something I and others have been writing
consistently and repeatedly in code reviews.
llvm-svn: 280419
The statement on using #if 0 ... #endif is not very clear (for people like me
:-)). This patch clarifies it a bit to avoid confusion.
Differential Revision: https://reviews.llvm.org/D23404
llvm-svn: 278932
such as std::equal on the third argument. This reverts previous workarounds.
Predefining _DEBUG_POINTER_IMPL disables Visual C++ 2013 headers from defining
it to a function performing the null pointer check. In practice, it's not that
bad since any function actually using the nullptr will seg fault. The other
iterator sanity checks remain enabled in the headers.
Reviewed by Aaron Ballmanþ and Duncan P. N. Exon Smith.
llvm-svn: 245711
It didn't seem worth leaving behind a guideline to use '= delete' to
make a class uncopyable. That's a well known C++ design pattern.
Reported on the mailing list and in PR22724.
llvm-svn: 230776
Rather than define our own standards, we adopt a set of best practices that
are already in use by the Go community.
Differential Revision: http://reviews.llvm.org/D5761
llvm-svn: 219646
I should have included this as part of r215986, which worked around this
corner by changing ArrayRef::equals() not to use std::equal. Alas.
llvm-svn: 215988
Clang-cl supports MSVC-style RTTI now, and we can even compile
typeid(...) with /GR-. Just don't instantiate std::function with a
polymorphic type, or bad things will happen.
llvm-svn: 212148
James Henderson