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
This patch adds initial argmemonly inference, by checking the underlying
objects of locations returned by MemoryLocation.
I think this should cover most cases, except function calls to other
argmemonly functions.
I'm not sure if there's a reason why we don't infer those yet.
Additional argmemonly can improve codegen in some cases. It also makes
it easier to come up with a C reproducer for 7662d1687b09 (already fixed,
but I'm trying to see if C/C++ fuzzing could help to uncover similar
issues.)
Compile-time impact:
NewPM-O3: +0.01%
NewPM-ReleaseThinLTO: +0.03%
NewPM-ReleaseLTO+g: +0.05%
https://llvm-compile-time-tracker.com/compare.php?from=067c035012fc061ad6378458774ac2df117283c6&to=fe209d4aab5b593bd62d18c0876732ddcca1614d&stat=instructions
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D121415
