Patch by David Grayson!

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Summary:
In r247104 I added the builtins for generating non-temporal memory operations,
but now I realized that they lack documentation. This patch adds some.

Differential Revision: http://reviews.llvm.org/D12785

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This patch depends on r246688 (D12341).

The goal is to make LLVM generate different code for these functions for a target that
has cheap branches (see PR23827 for more details):

int foo();

int normal(int x, int y, int z) {
   if (x != 0 && y != 0) return foo();
   return 1;
}

int crazy(int x, int y) {
   if (__builtin_unpredictable(x != 0 && y != 0)) return foo();
   return 1;
}

Differential Revision: http://reviews.llvm.org/D12458



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This change adds the new unroll metadata "llvm.loop.unroll.enable" which directs
the optimizer to unroll a loop fully if the trip count is known at compile time, and
unroll partially if the trip count is not known at compile time. This differs from
"llvm.loop.unroll.full" which explicitly does not unroll a loop if the trip count is not
known at compile time

With this change "#pragma unroll" generates "llvm.loop.unroll.enable" rather than
"llvm.loop.unroll.full" metadata. This changes the semantics of "#pragma unroll" slightly
to mean "unroll aggressively (fully or partially)" rather than "unroll fully or not at all".

The motivating example for this change was some internal code with a loop marked
with "#pragma unroll" which only sometimes had a compile-time trip count depending
on template magic. When the trip count was a compile-time constant, everything works
as expected and the loop is fully unrolled. However, when the trip count was not a
compile-time constant the "#pragma unroll" explicitly disabled unrolling of the loop(!).
Removing "#pragma unroll" caused the loop to be unrolled partially which was desirable
from a performance perspective.



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Support for emitting libcalls for __atomic_fetch_nand and
__atomic_{add,sub,and,or,xor,nand}_fetch was missing; add it, and some
test cases.

Differential Revision: http://reviews.llvm.org/D10847

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This change updates the documentation for the loop unrolling pragma behavior
change in r242047. Specifically, with that change "#pragma unroll" will not
unroll loops with a runtime trip count.



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Protection against stack-based memory corruption errors using SafeStack: Clang command line option and function attribute

This patch adds the -fsanitize=safe-stack command line argument for clang,
which enables the Safe Stack protection (see http://reviews.llvm.org/D6094
for the detailed description of the Safe Stack).

This patch is our implementation of the safe stack on top of Clang. The
patches make the following changes:

- Add -fsanitize=safe-stack and -fno-sanitize=safe-stack options to clang
  to control safe stack usage (the safe stack is disabled by default).

- Add __attribute__((no_sanitize("safe-stack"))) attribute to clang that can be
  used to disable the safe stack for individual functions even when enabled
  globally.

Original patch by Volodymyr Kuznetsov and others at the Dependable Systems
Lab at EPFL; updates and upstreaming by myself.

Differential Revision: http://reviews.llvm.org/D6095

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Fixes PR18985

Patch by Vassil Vassilev!

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Added a new preprocessor macro: __has_declspec_attribute. This can be used as a way to determine whether Clang supports a __declspec spelling for a given attribute, similar to  __has_attribute and __has_cpp_attribute.

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r142020 added support for has_feature(cxx_alignas). This does the same for
alignof.


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Complete support for the SD-6 standing document (based off N4200) with support for __has_cpp_attribute.

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which we don't yet implement).


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Adds a Clang-specific implementation of C11's stdatomic.h header. On systems,
such as FreeBSD, where a stdatomic.h header is already provided, we defer to
that header instead (using our __has_include_next technology). Otherwise, we
provide an implementation in terms of our __c11_atomic_* intrinsics (that were
created for this purpose).

C11 7.1.4p1 requires function declarations for atomic_thread_fence,
atomic_signal_fence, atomic_flag_test_and_set,
atomic_flag_test_and_set_explicit, and atomic_flag_clear, and requires that
they have external linkage. Accordingly, we provide these declarations, but if
a user elides the shadowing macros and uses them, then they must have a libc
(or similar) that actually provides definitions.

atomic_flag is implemented using _Bool as the underlying type. This is
consistent with the implementation provided by FreeBSD and also GCC 4.9 (at
least when __GCC_ATOMIC_TEST_AND_SET_TRUEVAL == 1).

Patch by Richard Smith (rebased and slightly edited by me -- Richard said I
should drive at this point).

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This makes use of the recently-added @llvm.assume intrinsic to implement a
__builtin_assume(bool) intrinsic (to provide additional information to the
optimizer). This hooks up __assume in MS-compatibility mode to mirror
__builtin_assume (the semantics have been intentionally kept compatible), and
implements GCC's __builtin_assume_aligned as assume((p - o) & mask == 0). LLVM
now contains special logic to deal with assumptions of this form.

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Added cast operations to the table of vector operations. Supported status 'no' means that there are no tests in the Clang test suite for the given cast.


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  "vf[0]" ==> "vs[0]"



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In unroll pragma syntax and loop hint metadata, change "enable" forms to a new form using the string "full".

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Add documentations for ACLE memory barrier intrinsics, describing their motion
barrier characteristics.


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Also consolidate 'backward compatibility'

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ARMv8 adds (to both AArch32 and AArch64) acquiring and releasing
variants of the exclusive operations, in line with the C++11 memory
model.

This adds support for two new intrinsics to expose them to C & C++
developers directly: __builtin_arm_ldaex and __builtin_arm_stlex, in
direct analogy with the versions with no implicit barrier.

rdar://problem/15885451

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Extend the documentation for "#pragma clang loop" hints to include the unroll
and unroll_count directives.

Patch by Mark Heffernan [http://reviews.llvm.org/D4198]



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Reviewed by: Aaron Ballman and Dmitri Gribenko


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to the normal non-placement ::operator new and ::operator delete, but allow
optimizations like new-expressions and delete-expressions do.


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This keeps Clang consistent with backend naming conventions.

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cxx_decltype_auto, and fix documentation of cxx_generic_lambdas and
cxx_init_captures to specify the right feature-check name.


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This adds Clang support for the ARM64 backend. There are definitely
still some rough edges, so please bring up any issues you see with
this patch.

As with the LLVM commit though, we think it'll be more useful for
merging with AArch64 from within the tree.

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Moving the documentation for the type safety checking attributes into AttrDocs. If a custom heading is provided, do not automatically generate the alternate spelling list. This is necessary because some attributes have distinct semantic spellings and meanings, but use the same semantic attribute internally. Such attributes should have multiple elements in their documentation list, but not show all spellings. At some point, it would be nice to have a way to attach the documentation element to a specific spelling for these cases.

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Doing some temporary touch-up on the gnu namespace attribute documentation, from a post-commit review comment.

Ideally, this content will eventually find a home with the rest of the attribute documentation.

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Refactored the way attribute category headers are handled so that it is possible to use custom categories. This allows for moving the consumable attributes (consumable, callable_when, return_typestate, etc) to be grouped together, with a content heading, like they were in the language extensions documentation. Moved the consumable attribute documentation from the language extensions into the attribute documentation table.

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