Avoid constructing invalid ConstantRange when Offset + Length in memset
overflows signed 64-bit integer space. This prevents assertion failures
when inferring the initializes attribute.
Fixes#140345
Per LangRef volatile operations can read and write inaccessible memory:
> any volatile operation can read and/or modify state which is not
> accessible via a regular load or store in this module
Model this by adding inaccessible memory effects in getMemoryEffects()
if the operation is volatile.
In the future, we should model volatile using operand bundles instead.
Fixes https://github.com/llvm/llvm-project/issues/120932.
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.
Bail out negative length while inferring initializes attr. Otherwise it
causes an assertion error:
`Attribute 'initializes' does not support unordered ranges`
