Summary:
Right now we annotate C++'s `operator new` with `noalias` attribute,
which very much is healthy for optimizations.
However as per [[ http://eel.is/c++draft/basic.stc.dynamic.allocation | `[basic.stc.dynamic.allocation]` ]],
there are more promises on global `operator new`, namely:
* non-`std::nothrow_t` `operator new` *never* returns `nullptr`
* If `std::align_val_t align` parameter is taken, the pointer will also be `align`-aligned
* ~~global `operator new`-returned pointer is `__STDCPP_DEFAULT_NEW_ALIGNMENT__`-aligned ~~ It's more caveated than that.
Supplying this information may not cause immediate landslide effects
on any specific benchmarks, but it for sure will be healthy for optimizer
in the sense that the IR will better reflect the guarantees provided in the source code.
The caveat is `-fno-assume-sane-operator-new`, which currently prevents emitting `noalias`
attribute, and is automatically passed by Sanitizers ([[ https://bugs.llvm.org/show_bug.cgi?id=16386 | PR16386 ]]) - should it also cover these attributes?
The problem is that the flag is back-end-specific, as seen in `test/Modules/explicit-build-flags.cpp`.
But while it is okay to add `noalias` metadata in backend, we really should be adding at least
the alignment metadata to the AST, since that allows us to perform sema checks on it.
Reviewers: erichkeane, rjmccall, jdoerfert, eugenis, rsmith
Reviewed By: rsmith
Subscribers: xbolva00, jrtc27, atanasyan, nlopes, cfe-commits
Tags: #llvm, #clang
Differential Revision: https://reviews.llvm.org/D73380
I am planning to use this feature to make update_cc_test_checks.py less fragile
by obtaining the mangled names directly from -ast-dump=json. Currently,
it uses c-index-test which ignores the -triple=, etc. arguments that are
in the RUN: line and therefore does not generate checks for some targets.
The AST dump tests were updated using the following command:
`python $LLVM_BINDIR/gen_ast_dump_json_test.py --update --source $LLVM_SRC/clang/test/AST/*-json.*`
Reviewers: aaron.ballman
Reviewed By: aaron.ballman
Subscribers: rsmith, MaskRay, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D69564
This adds information about the offset within the source file to the given source location as well as information about the include file a location is from. These pieces of information allow for more efficient post-processing of JSON AST dumps.
llvm-svn: 374921
Rather than create JSON objects for source locations and ranges, we instead stream them out directly. This allows us to elide duplicate information (without JSON field reordering causing an issue) like file names and line numbers, similar to the text dump. This also adds token length information when dumping the source location.
llvm-svn: 364226
This also details what filters, if any, were used to generate the test output. Updates all the current JSON testing files to include the automated note.
llvm-svn: 364055
Previously, we attempted to write out template parameters and specializations to their own array, but due to the architecture of the ASTNodeTraverser, this meant that other nodes were not being written out. This now follows the same behavior as the regular AST dumper and puts all the (correct) information into the "inner" array. When we correct the AST node traverser itself, we can revisit splitting this information into separate arrays again.
llvm-svn: 363819
Roman Lebedev