This relands commit f890f010.

The result value of `getelementptr inbounds (TY, null, not zero)` is a poison value.
We can think of it as undefined behavior.

This relands commit b6a0be8c.

Return undefined to a noundef return value is undefined.

Example:

```
define noundef i32 @test_ret_noundef(i1 %cond) {
entry:
  br i1 %cond, label %bb1, label %bb2
bb1:
  br label %bb2
bb2:
  %r = phi i32 [ undef, %entry ], [ 1, %bb1 ]
  ret i32 %r
}
```

Turns out the problem with
https://github.com/llvm/llvm-project/issues/60013 is due to the fact
that order of operation is unspecified in C++:
https://en.cppreference.com/w/cpp/language/eval_order. A small example
of where this manifests with MSVC can be seen here
https://ooo.godbolt.org/z/bxqKeqzqn.

This patch does the following:
* Removes the addition operations where we sequence more than one
side-effect based expression.
* Removes test guards to now run on Windows

This is to fix the bug reported in
https://discourse.llvm.org/t/whats-the-recommended-way-to-use-prop-dict/75921



When `prop-dict` is used in the assembly format, `attr-dict` should
print discardable attributes only.

Co-authored-by: Arthurq Qiu <arthurq@nvidia.com>

weak ordering.
Try to make PHICompare to meat strict weak ordering criteria.

async just takes an integral value, but it has a little bit of special
rules in sema, so it is implemented slightly differently than int-expr.

This patch implements async parsing.

…ctor CC.

This reverts commit 92470131. Causes compilation
errors on valid code, see
https://github.com/llvm/llvm-project/pull/77768#issuecomment-1908062472.

This reverts commit aaa93ce7.

This commit was not properly reviewed.

It is not fix-sized anymore.

```
AppProperties app;
```
is marked as a weak symbol in header now. One can just use `&app !=
nullptr` to check if `app` is defined. There is no need to define it for
overlay mode.

Fixes a regression from #78041 as reported in the review.  The original
patch failed to compare the canonical type, which this adds.  A slightly
modified test of the original report is added.

RISC-V is mentioned elsewhere in the document it seems like it should be
mentioned in the introduction.

Unconditionally change std::string's alignment to 8.

This change saves memory by providing the allocator more freedom to
allocate the most
efficient size class by dropping the alignment requirements for
std::string's
pointer from 16 to 8. This changes the output of std::string::max_size,
which makes it ABI breaking.

That said, the discussion concluded that we don't care about this ABI
break. and would like this change enabled universally.

The ABI break isn't one of layout or "class size", but rather the value
of "max_size()" changes, which in turn changes whether `std::bad_alloc`
or `std::length_error` is thrown for large allocations.

This change is the child of PR #68807, which enabled the change behind
an ABI flag.

Summary:
The offloading wrapper is a object file that contains code necessary to
register offloading entries for the given runtime. Currently, we
expected only one of these to be present when we make the final
executable. However, in the case of redistributable linking with `-r` we
can end up with multiple of these being generated before finally
creating the executable.

This patch simply changes the defintiions of these globals to be
mergable. This allows multiples of these to participate in a single link
job. For ELF, we just make the dummy variable internal and used so it
sets up the section as expected. For COFF we make the entries weak_odr
so they merge to a single symbol

Summary:
A relocatable link through `clang -r` can go through the
clang-linker-wrapper if offloading is enabled. This will have the effect
of linking the device code and creating the wrapper module. It will then
be merged into the final file. This is useful behavior on its own, but
is likely not what is expected for a `-r` job.

This patch makes the linker wrapper ignore the device code when doing a
reloctable link. This has the effect of the linker merging the
`.llvm.offloading` sections in the output object. These will then be
parsed as normal when the executable is finally created.

Even though this doesn't actually perform a reloctable link on the
device code itself, it has a similar effect of combining multiple files
into a single one.

[mlir][sparse] setup `SparseIterator` to help generating code to traverse a sparse tensor level. (#78345)

before erasing.

Before trying to erase the extractelement instruction, not enough to
check for single use, need to check that it is not used in several nodes
because of the preliminary nodes reordering.

The implementation of raw_string_ostream::write_impl() was moved to
raw_socket_stream.cpp when the raw_socket_ostream support was separated.
This patch moves it back to facilitate disabling socket support in
downstream projects.

Machines with vector support handle i128 in vector registers and
therefore only have the small displacement available for memory
accesses. Update isLegalAddressingMode() to reflect this.

The faults on invalid vec range in mincore seems to be handled
differently by the OS (it is an erroneous edge case after all). Remove
the tests for now.

When creating a new UsingType, the underlying type may change if it is a
declaration. This creates an inconsistency between the type searched and
type created. Update member and non-member Profile functions so that
they return the same ID.

Akin the `py_binary` rules for `lit`, these are scoped to binaries,
rather than exposing the library - binary split. The latter is available
to the package (pip package) users.

Tested:

```
cd utils/bazel
bazel build @llvm-project//llvm:extract_ir
bazel-bin/external/llvm-project/llvm/extract_ir --help
```
...and observed expected output (rather than import not found errors)

(Same for the other 2 targets).

This reverts commit be08be5d.
The build error was due to a different change, apologies!

b1ae461a renamed Cycle ->
ReleaseAtCycle.

7e09239e was committed without rebasing
but used the old Cycle syntax.

This caused a build failure when
7e09239e was squash-and-merged. This
patch fixes this problem.

This reverts commit 32f79226.

Doesn't build, see
https://github.com/llvm/llvm-project/pull/79205#issuecomment-1908730527

TargetSchedule.td explicitly allows the usage of a ProcResource for zero
cycles, in order to represent that the ProcResource must be available
but is not consumed by the instruction. On the other hand,
ResourceSegments explicitly does not allow for a zero sized interval. In
order to remedy this, this patch handles the special case of when there
is an empty interval usage of a resource by not adding an empty
interval.

We ran into this issue downstream, but it makes sense to have
this upstream since it is explicitly allowed by TargetSchedule.td.

In Bazel, Clang current separates the clang executable into a
clang-driver library, and the actual clang executable. This allows
downstream users to make their own variations of clang, without having
to redo/maintain separate build pipelines.

This adds the same for opt for both CMake and Bazel.

[libc][NFC] Fix `-DSHOW_INTERMEDIATE_OBJECTS=DEPS` to work properly for entry points and unit tests. (#79254)