As mentioned on llvm-dev, this is a new documentation page intended to collect tips for frontend authors on how to generate IR that LLVM is able to optimize well. These types of things come up repeated in review threads and it would be good to have a place to save them.
I added a small handful to start us off, but I mostly want to get the framework in place. Once the docs are here, we can add to them incrementally. If you know of something appropriate for this page, please add it!
Differential Revision: http://reviews.llvm.org/D7890
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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.
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When I originally committed the statepoint docs, I left placeholders for example IR fragments. I'm finally getting around to filling those in.
I also added IR fragments to illustrate the usage of the PlaceSafepoints pass while I was at it.
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Add a brief section linking to the experimental statepoint intrinsics analogous to the one we have linking to patchpoint.
While I'm here, cleanup some wording about what the gc "name" attribute actually means. It's not the name of a *collector* it's the name of the *strategy* which may be compatible with multiple collectors.
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The builder is based on a layout algorithm that tries to keep members of
small bit sets together. The new layout compresses Chromium's bit sets to
around 15% of their original size.
Differential Revision: http://reviews.llvm.org/D7796
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This is still gcroot vs gc.statepoint agnostic. I'm just trying to clarify the general documentation at this point.
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In this change:
- Put the getting started section first
- Create a dedicated section to document the built in collector strategies
- Move discuss of ShadowStack into new section
- Add placeholders for erlang, ocaml, and statepoint-example collectors
There will be many more changes following. I plan on full integrating the documentation for gc.statepoint and gc.root. I want to make it much clearer on how to get started and what users should expect in terms of effort.
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This patch introduces a new mechanism that allows IR modules to co-operatively
build pointer sets corresponding to addresses within a given set of
globals. One particular use case for this is to allow a C++ program to
efficiently verify (at each call site) that a vtable pointer is in the set
of valid vtable pointers for the class or its derived classes. One way of
doing this is for a toolchain component to build, for each class, a bit set
that maps to the memory region allocated for the vtables, such that each 1
bit in the bit set maps to a valid vtable for that class, and lay out the
vtables next to each other, to minimize the total size of the bit sets.
The patch introduces a metadata format for representing pointer sets, an
'@llvm.bitset.test' intrinsic and an LTO lowering pass that lays out the globals
and builds the bitsets, and documents the new feature.
Differential Revision: http://reviews.llvm.org/D7288
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If the landingpad of the invoke is using a personality function that
catches asynch exceptions, then it can catch a trap.
Also add some landingpads to invalid LLVM IR test cases that lack them.
Over-the-shoulder reviewed by David Majnemer.
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Summary:
The CMake configuration is explicitely looking for Debug build, all the
other variant disable assertions.
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D7359
From: Mehdi Amini <mehdi.amini@apple.com>
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Remove handling for DW_TAG_constant. We started producing it in
r110656, but reverted that in r110876 without dropping the support.
Finish the job.
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This is a refactoring to restructure the single user of performCustomLowering as a specific lowering pass and remove the custom lowering hook entirely.
Before this change, the LowerIntrinsics pass (note to self: rename!) was essentially acting as a pass manager, but without being structured in terms of passes. Instead, it proxied calls to a set of GCStrategies internally. This adds a lot of conceptual complexity (i.e. GCStrategies are stateful!) for very little benefit. Since there's been interest in keeping the ShadowStackGC working, I extracting it's custom lowering pass into a dedicated pass and just added that to the pass order. It will only run for functions which opt-in to that gc.
I wasn't able to find an easy way to preserve the runtime registration of custom lowering functionality. Given that no user of this exists that I'm aware of, I made the choice to just remove that. If someone really cares, we can look at restoring it via dynamic pass registration in the future.
Note that despite the large diff, none of the lowering code actual changes. I added the framing needed to make it a pass and rename the class, but that's it.
Differential Revision: http://reviews.llvm.org/D7218
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Again, I'd like to emphasize to everyone that this sort of markup change
is *not* what you should be concerned about when writing docs. Focus on
*content*.
I applaud Chandler for focusing on the fantastic content of this new
section!
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polymorphism, and virtual dispatch.
This is essentially trying to explain the emerging design techniques
being used in LLVM these days somewhere more accessible than the
comments on a particular piece of infrastructure. It covers the
"concepts-based polymorphism" that caused some confusion during initial
reviews of the new pass manager as well as the tagged-dispatch mechanism
used pervasively in LLVM and Clang.
Perhaps most notably, I've tried to provide some criteria to help
developers choose between these options when designing new pieces of
infrastructure.
Differential Revision: http://reviews.llvm.org/D7191
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The number of lines of code in Kaleidoscope has risen from the
previously reported 700 to 986 according to the cloc tool. This tools
was run on the toy.cpp file from Chapter 8.
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Specifically, gc.result benefits from this greatly. Instead of:
gc.result.int.*
gc.result.float.*
gc.result.ptr.*
...
We now have a gc.result.* that can specialize to literally any type.
Differential Revision: http://reviews.llvm.org/D7020
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