This PR removes the old `nocapture` attribute, replacing it with the new
`captures` attribute introduced in #116990. This change is
intended to be essentially NFC, replacing existing uses of `nocapture`
with `captures(none)` without adding any new analysis capabilities.
Making use of non-`none` values is left for a followup.

Some notes:
* `nocapture` will be upgraded to `captures(none)` by the bitcode
   reader.
* `nocapture` will also be upgraded by the textual IR reader. This is to
   make it easier to use old IR files and somewhat reduce the test churn in
   this PR.
* Helper APIs like `doesNotCapture()` will check for `captures(none)`.
* MLIR import will convert `captures(none)` into an `llvm.nocapture`
   attribute. The representation in the LLVM IR dialect should be updated
   separately.

reland https://github.com/llvm/llvm-project/pull/97373 after fixing
clang tests.

Confirmed with "ninja check-llvm" and "ninja check-clang"

This reverts commit 661c593850715881d2805a59e90e6d87d8b9fbb8.

Multiple buildbot failures, e.g. https://lab.llvm.org/buildbot/#/builders/108/builds/6096

Add the "initializes" attribute inference.

This change is expected to have ~0.09% compile time regression, which
seems acceptable for interprocedural DSE.

https://llvm-compile-time-tracker.com/compare.php?from=9f10252c4ad7cffbbcf692fa9c953698f82ac4f5&to=56345c1cee4375eb5c28b8e7abf4803d20216b3b&stat=instructions%3Au

This patch adds missing `norecurse` attrs to funcs that only call intrinsics with `nocallback` attrs.
Fixes the regression found in https://github.com/dtcxzyw/llvm-opt-benchmark/pull/45#discussion_r1436148743.
The function loses `norecurse` attr because it calls `@llvm.fabs.f64`, which is not marked as `norecurse`.

Since `norecurse` is not a default attribute of intrinsics and it is
ambiguous for intrinsics, I decided to use the existing `callback`
attributes.

> nocallback
This attribute indicates that the function is only allowed to jump back
into caller’s module by a return or an exception, and is not allowed to
jump back by invoking a callback function, a direct, possibly
transitive, external function call, use of longjmp, or other means. It
is a compiler hint that is used at module level to improve dataflow
analysis, dropped during linking, and has no effect on functions defined
in the current module.

See also https://llvm.org/docs/LangRef.html#function-attributes.

Fixes #68270

The function attribute analysis handles many instructions, like
addrspacecast, which do not themselves read or write memory but which
transform pointers into other values in the same alias set.

There are intrinsic functions, such as ptrmask or the AMDGPU-specific
make.buffer.rsrc, which also preserve membership in alias sets without
capturing. This commit adds the addrspacecast-like behavior to these
calls.

When inferring readonly/writeonly on arguments, if the argument is
passed to a call, we should only check the ArgMem effects implied by the
call -- we don't care whether the call reads/writes non-arg memory
(captured pointers are not relevant here, because they will abort the
analysis entirely).

This also fixes a regression that was introduced when moving to
MemoryEffects: The code was still checking the old WriteOnly attribute
on functions, which no longer exists.

Add tests with argmem variations.

This patch adds a lightweight instance of Attributor that only deduces
attributes.

This is just an initial version with the goal to have a version that
only focuses on attributes to replace the function-attrs pass.

The initial version has a few open issues pending until default
enablement, the main one probably being compile time. The main
additional functionality this will provide in general is propagating
attributes to call sites.

Open issues:

* compile time
  The current version increase O3 +2.67% and ThinLTO +6.18% when replacing FunctionAttr
   https://llvm-compile-time-tracker.com/compare.php?from=c4bb3e073548cf436d5fa0406e3ae75e94684dec&to=d992630a69c79a2587d736e6a88f448850413bd1&stat=instructions%3Au
   Both are with an additional change to preserve more analysis, like FunctionAttrs CGSCC run.

* some missed attribute inference

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D152081

This switches everything to use the memory attribute proposed in
https://discourse.llvm.org/t/rfc-unify-memory-effect-attributes/65579.
The old argmemonly, inaccessiblememonly and inaccessiblemem_or_argmemonly
attributes are dropped. The readnone, readonly and writeonly attributes
are restricted to parameters only.

The old attributes are auto-upgraded both in bitcode and IR.
The bitcode upgrade is a policy requirement that has to be retained
indefinitely. The IR upgrade is mainly there so it's not necessary
to update all tests using memory attributes in this patch, which
is already large enough. We could drop that part after migrating
tests, or retain it longer term, to make it easier to import IR
from older LLVM versions.

High-level Function/CallBase APIs like doesNotAccessMemory() or
setDoesNotAccessMemory() are mapped transparently to the memory
attribute. Code that directly manipulates attributes (e.g. via
AttributeList) on the other hand needs to switch to working with
the memory attribute instead.

Differential Revision: https://reviews.llvm.org/D135780