This patch adds support for a `header` declaration in a module map to specify
certain `stat` information (currently, size and mtime) about that header file.
This has two purposes:

- It removes the need to eagerly `stat` every file referenced by a module map.
  Instead, we track a list of unresolved header files with each size / mtime
  (actually, for simplicity, we track submodules with such headers), and when
  attempting to look up a header file based on a `FileEntry`, we check if there
  are any unresolved header directives with that `FileEntry`'s size / mtime and
  perform deferred `stat`s if so.

- It permits a preprocessed module to be compiled without the original files
  being present on disk. The only reason we used to need those files was to get
  the `stat` information in order to do header -> module lookups when using the
  module. If we're provided with the `stat` information in the preprocessed
  module, we can avoid requiring the files to exist.

Unlike most `header` directives, if a `header` directive with `stat`
information has no corresponding on-disk file the enclosing module is *not*
marked unavailable (so that behavior is consistent regardless of whether we've
resolved a header directive, and so that preprocessed modules don't get marked
unavailable). We could actually do this for all `header` directives: the only
reason we mark the module unavailable if headers are missing is to give a
diagnostic slightly earlier (rather than waiting until we actually try to build
the module / load and validate its .pcm file).

Differential Revision: https://reviews.llvm.org/D33703


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Check pointer arithmetic for overflow.

For some more background on this check, see:

  https://wdtz.org/catching-pointer-overflow-bugs.html
  https://reviews.llvm.org/D20322

Patch by Will Dietz and John Regehr!

This version of the patch is different from the original in a few ways:

  - It introduces the EmitCheckedInBoundsGEP utility which inserts
    checks when the pointer overflow check is enabled.

  - It does some constant-folding to reduce instrumentation overhead.

  - It does not check some GEPs in CGExprCXX. I'm not sure that
    inserting checks here, or in CGClass, would catch many bugs.

Possible future directions for this check:

  - Introduce CGF.EmitCheckedStructGEP, to detect overflows when
    accessing structures.

Testing: Apart from the added lit test, I ran check-llvm and check-clang
with a stage2, ubsan-instrumented clang. Will and John have also done
extensive testing on numerous open source projects.

Differential Revision: https://reviews.llvm.org/D33305

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Summary: In order for libc++ to add `<experimental/coroutine>` to its module map, there has to be a feature that can be used to detect if coroutines support is enabled in Clang. 

Reviewers: rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D33538

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This reverts commit r304054.

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Summary: In order for libc++ to add `<experimental/coroutine>` to its module map, there has to be a feature that can be used to detect if coroutines support is enabled in Clang. 

Reviewers: rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D33538

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Adapt to changes made in r302499.

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DontAlign

This converts the clang-format option AlignEscapedNewlinesLeft from a
boolean to an enum, named AlignEscapedNewlines, with options Left (prev.
true), Right (prev. false), and a new option DontAlign.

When set to DontAlign, the backslashes are placed just after the last token in each line:
  #define EXAMPLE \
    do { \
        int x = aaaaa; \
        int b; \
        int dddddddddd; \
    } while (0)

Patch by jtbandes. Thank you!

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Patch by Roman Lebedev.

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[sanitizer-coverage] implement -fsanitize-coverage=no-prune,... instead of a hidden -mllvm flag. clang part.

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Summary:
This adds a new ASTMatcher for CXXStdInitializerListExprs that matches C++ initializer list expressions.

The primary motivation is to use it to fix [[ https://bugs.llvm.org/show_bug.cgi?id=32896 | PR32896 ]] (review here [[ https://reviews.llvm.org/D32767 | D32767 ]]).

Reviewers: alexfh, Prazek, aaron.ballman

Reviewed By: alexfh, aaron.ballman

Subscribers: malcolm.parsons, cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D32810

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Patch by Roman Lebedev.

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This reverts commit r300295.

It's no longer true, print_stacktrace=1 is supported on Darwin/Windows
as of r301839.

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Currently we have #include <Sema.h> in the doxygen page documenting Sema. The
patch changes it ot #include "clang/Sema/Sema.h" which is what we would spell if
we need to include it in a real codebase.

Patch by Yuka Takahashi (D32113)!


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This is a recommit of r300539 that was reverted in r300543 due to test failures.
The original commit message is displayed below:

The new '#pragma clang attribute' directive can be used to apply attributes to
multiple declarations. An attribute must satisfy the following conditions to
be supported by the pragma:
- It must have a subject list that's defined in the TableGen file.
- It must be documented.
- It must not be late parsed.
- It must have a GNU/C++11 spelling.

Differential Revision: https://reviews.llvm.org/D30009


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Some tests fail on the Windows buildbots. I will have to investigate more.
This commit reverts r300539, r300540 and r300542.


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The new '#pragma clang attribute' directive can be used to apply attributes to
multiple declarations. An attribute must satisfy the following conditions to
be supported by the pragma:
- It must have a subject list that's defined in the TableGen file.
- It must be documented.
- It must not be late parsed.
- It must have a GNU/C++11 spelling.

Differential Revision: https://reviews.llvm.org/D30009


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Printing out stack traces along with UBSan diagnostics is unsupported on
Darwin. That's because it isn't possible to use the fast unwinder or the
slow unwinder.

Apparently, it's inappropriate to use the fast unwinder for UBSan
issues. I'm not exactly sure why (see the comment in ubsan_diag.cc).
Forcing use of the fast unwinder produces decent results, AFAICT.

Darwin also does not appear to have a slow unwinder suitable for use
with the sanitizers. Apparently that's because of PR20800 [1][2]. But
that bug has been fixed. I'm not sure if there is anything preventing
use of the slow unwinder now.

Currently, passing UBSAN_OPTIONS=print_stacktrace=1 does nothing on
Darwin. This isn't good, but it might be a while before we can fix the
situation, so we should at least document it.

[1] https://github.com/google/sanitizers/issues/137
"We can't use the slow unwinder on OSX now, because Clang produces
incorrect unwind info for the ASan runtime functions on OSX
(http://llvm.org/PR20800)."

[2] https://bugs.llvm.org/show_bug.cgi?id=20800
Bug 20800 - Invalid compact unwind info generated for a function without
frame pointers on OSX

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Summary:
[LWG 2911](http://cplusplus.github.io/LWG/lwg-defects.html#2911) adds `std::is_aggregate` to the library, which requires a new builtin trait. This patch implements `__is_aggregate`.


Reviewers: rsmith, majnemer, aaron.ballman

Reviewed By: aaron.ballman

Subscribers: STL_MSFT, cfe-commits

Differential Revision: https://reviews.llvm.org/D31513

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One way to currently test the reproducers is to setup
"FORCE_CLANG_DIAGNOSTICS_CRASH=1" before invoking clang. This simulates
a crash and produces the same contents needed by the reproducers.  The
reproducers are specially useful when triaging Modules issues, not only
on crashes, but also for reproducing misleading warnings, errors, etc.

Add a '-gen-reproducer' driver option to clang (or any similar name) and
give users a flag option.

Note that clang already has a -fno-crash-diagnostics, which disables the
crash reproducers. I've decided not to propose "-fcrash-diagnostics"
since it doesn't convey the ideia of reproduction despite a crash.

rdar://problem/24114619

Differential Revision: https://reviews.llvm.org/D27604

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Reviewers: djasper

Reviewed By: djasper

Subscribers: Eugene.Zelenko, klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D31408

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docs: Use the term "whole-program devirtualization" instead of "virtual function call optimization".

The former term is probably more familiar to users. Also add references to
the command line flags used to enable the features described in the doc.

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clang-format <<END
auto c1 = u8'a';
auto c2 = u'a';
END

Before:
  auto c1 = u8 'a';
  auto c2 = u'a';

Now:
  auto c1 = u8'a';
  auto c2 = u'a';

Patch from Denis Gladkikh <llvm@denis.gladkikh.email>!


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This adds the new pragma and the first variant, contract(on/off/fast).

The pragma has the same block scope rules as STDC FP_CONTRACT, i.e. it can be
placed at the beginning of a compound statement or at file scope.

Similarly to STDC FP_CONTRACT there is no need to use attributes.  First an
annotate token is inserted with the parsed details of the pragma.  Then the
annotate token is parsed in the proper contexts and the Sema is updated with
the corresponding FPOptions using the shared ActOn function with STDC
FP_CONTRACT.

After this the FPOptions from the Sema is propagated into the AST expression
nodes.  There is no change here.

I was going to add a 'default' option besides 'on/off/fast' similar to STDC
FP_CONTRACT but then decided against it. I think that we'd have to make option
uppercase then to avoid using 'default' the keyword.  Also because of the
scoped activation of pragma I am not sure there is really a need a for this.

Differential Revision: https://reviews.llvm.org/D31276

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Reviewers: hokein, aaron.ballman

Reviewed By: aaron.ballman

Subscribers: aaron.ballman, cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D28671

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Reviewers: rsmith, rizsotto.mailinglist

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D31133

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The alias was only ever used on darwin and had some issues there,
and isn't used in practice much. Also fixes a problem with -mno-altivec
not turning off -maltivec.

Also add a diagnostic for faltivec/fno-altivec that directs users to use
maltivec options and include the altivec.h file explicitly.

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PR32346 suggests that UBSan's docs about the -fsanitize,
-fno-sanitize-recover, and -fsanitize-trap options are not explicit
enough. Try to improve the wording.

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Summary: Proposal: Backward-edge CFI for return statements (RCFI)

Reviewers: pcc, eugenis, krasin

Reviewed By: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31112

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