Adds a `target_specific_attrs` optional array attribute to
`mlir.global`, as well as conversions to and from LLVM attributes on
`llvm::GlobalVariable` objects. This is necessary to preserve unknown
attributes on global variables when converting to and from the LLVM
Dialect. Previously, any attributes on an `llvm::GlobalVariable` not
explicitly modeled by `mlir.global` were dropped during conversion.

Remove "approx-func-fp-math" attribute and related command line option,
users should always use afn flag in IR.
Resolve FIXME in `TargetMachine::resetTargetOptions` partially.

Adds the `#llvm.target<triple = $TRIPLE, chip = $CHIP, features =
$FEATURES>` attribute and along with a `-llvm-target-to-data-layout`
pass to derive a MLIR data layout from the LLVM data layout string
(using the existing `DataLayoutImporter`). The attribute implements the
relevant DLTI-interfaces, to expose the `triple`, `chip` (AKA `cpu`) and
`features` on `#llvm.target` and the full `DataLayoutSpecInterface`. The
pass combines the generated `#dlti.dl_spec` with an existing `dl_spec`
in case one is already present, e.g. a `dl_spec` which is there to
specify size of the `index` type.

Adds a `TargetAttrInterface` which can be implemented by all attributes
representing LLVM targets.

Similar to the Draft PR https://github.com/llvm/llvm-project/pull/78073.

RFC on which this PR is based:
https://discourse.llvm.org/t/mandatory-data-layout-in-the-llvm-dialect/85875

Adds support for the module level assembly in the LLVM IR dialect.

---------

Co-authored-by: Tobias Gysi <tobias.gysi@nextsilicon.com>

…(… (#151099)

This reverts commit 2780b8f22058b35a8e70045858b87a1966df8df3 and relands
b7bfbc0c4c7b20d6623a5b0b4a7fea8ae08a62da.

Adds the following fixes compared to the original PR
(https://github.com/llvm/llvm-project/pull/150783):
- A bazel fix
- Use `let methods` instead of `list<InterfaceMethod> methods`

The missing forward declaration has been added in meantime:
https://github.com/llvm/llvm-project/commit/9164d206b33d61c93f5fc4628797485f96d654ca.

Reverts llvm/llvm-project#151125

Broke the gcc-7 build:

include/mlir/Target/LLVMIR/ModuleTranslation.h:318:34: error: no type
named 'CallBase' in namespace 'llvm'
                           llvm::CallBase *call,
                           ~~~~~~^

…… (#151099)

This reverts commit 2780b8f22058b35a8e70045858b87a1966df8df3 to reland
59013d44058ef423a117f95092150e16e16fdb09.

In addition to the original commit this one includes:
- This includes a bazel fix
- Use `let methods` instead of `list<InterfaceMethod> methods`

The original commit message was:

This patch extends the LLVM dialect's intrinsic infra to support
argument and result attributes. Initial support is added for the memory
intrinsics llvm.intr.memcpy, llvm.intr.memmove, and llvm.intr.memset.

Additionally, an ArgAndResultAttrsOpInterface is factored out of
CallOpInterface and CallableOpInterface, enabling operations to have
argument and result attributes without requiring them to be a call or a
callable operation.

…#150783)"

This reverts commit 59013d44058ef423a117f95092150e16e16fdb09.

The change breaks a flang build bot:
https://lab.llvm.org/buildbot/#/builders/207/builds/4441

This patch extends the LLVM dialect's intrinsic infra to support
argument and result attributes. Initial support is added for the memory
intrinsics `llvm.intr.memcpy`, `llvm.intr.memmove`, and
`llvm.intr.memset`.

Additionally, an ArgAndResultAttrsOpInterface is factored out of
CallOpInterface and CallableOpInterface, enabling operations to have
argument and result attributes without requiring them to be a call or a
callable operation.