Identified with misc-include-cleaner.

The main use for this patch is LTO. It is not (yet?) possible to set the
size level (-Os, -Oz) in the linker, which means loops are still rotated
even if -Oz is specified on the command line. Therefore, look at the
function attribute instead of only at the size level to determine
whether to rotate loops for a given function.

For discussion, see: https://reviews.llvm.org/D119342

An older version of this patch was already approved at
https://reviews.llvm.org/D119342 but I never got around to committing
it. The code changed so I had to make some minor updates to this patch
and in the meantime I also lost commit access because I wasn't really
using it. So here is an updated patch.

This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...

`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.

There is a gap between running opt -Oz and running opt -passes="OZ_PASSES" where OZ_PASSES is taken from running opt -Oz -print-pipeline-passes.

One of the reasons causing this is that -Oz uses non-default setting for LoopRotate but LoopRotate does not expose its settings when printing the pipeline.

This commit fixes this by exposing LoopRotates parameters.

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D153437

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

Since std::optional does not offer getPointer(), this patch replaces
X.getPointer() with &*X to make the migration from llvm::Optional to
std::optional easier.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

Differential Revision: https://reviews.llvm.org/D138466

This patch replaces Optional::hasValue with the implicit cast to bool
in conditionals only.

This reverts commit aa8feeefd3ac6c78ee8f67bf033976fc7d68bc6d.