LLVM Weekly - #77, Jun 22nd 2015
Welcome to the seventy-seventh issue of LLVM Weekly, a weekly newsletter (published every Monday) covering developments in LLVM, Clang, and related projects. LLVM Weekly is brought to you by Alex Bradbury. Subscribe to future issues at https://llvmweekly.org and pass it on to anyone else you think may be interested. Please send any tips or feedback to asb@asbradbury.org, or @llvmweekly or @asbradbury on Twitter.
I'll be in California next week for the second RISC-V workshop. Me and my colleague Wei will both be giving talks about recent lowRISC progress. Say hi if you're going to be there. I might have some spare time towards the end of the week too if anyone wants to meet up.
News and articles from around the web
WebAssembly has been announced. It is a new collaboration between browser vendors to define a new binary executable format that can be used as a compilation target. A good summary is available here on the emscripten mailing list.
Tilmann Scheller has written up a pair of blog posts about improving build times of Clang. He steps through a wide range of generic approaches (using Ninja, ccache, the gold linker, LTO+PGO in the host compiler etc etc) and some specific to Clang/LLVM.
The Cambridge LLVM Social will be taking place on Wed 24th June, 7.30pm at the Blue.
On the mailing lists
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Dan Gohman has posted an RFC for the inclusion of a WebAssembly backend in LLVM. It seems like everyone is in favour of the proposed approach.
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Yaxun Li has posted a revised RFC on adding a SPIR-V target to LLVM. There still seems to be some push-back on the proposed approach. Chandler Carruth makes an argument that SPIR-V should make use of the existing SelectionDAG legalization layer.
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Igor Laevsky is seeking more feedback on adding an attribute to mark that a function only accesses memory through its arguments. Philip Reames point out in the thread that this isn't a new concept to LLVM, except right now such an attribute can only be specified on intrinsics.
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Philip Reames is looking for feedback on his plan to implement profile-guided inlining.
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Diego Novillo has posted an RFC to enable the -fprofile-generate and -fprofile-use Clang flags. Unsurprisingly, people are in favour of supporting these flags for GCC compatibility.
LLVM commits
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Some initial support for 'fault maps' and a
FAULTING_LOAD_OP, intended for use in a managed language runtime, has been added. The new ImplicitNullChecks pass will fold null checks into nearby memory operations. r239740, r239743. -
The SafeStack pass to protect against stack-based memory corruption errors has been added. r239761.
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All temporary symbols are now unnamed. This saves a small amount of memory. r240130.
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There's been some enhancement to the heuristics for switch lowering. r240224.
Clang commits
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The
-fsanitize-trap=flag has been introduced, which will be used to control if the given sanitizer traps upon detecting an error. r240105. -
Appropriate bitsets for use by LLVM's control flow integrity implementation can now be emitted for the Microsoft ABI. r240117.
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Kernel AddressSanitizer now has basic support. r240131.
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Clang learned to recognise type nullability specifiers. r240146.