As part of the "RemoveDIs" project, BasicBlock::iterator now carries a
debug-info bit that's needed when getFirstNonPHI and similar feed into
instruction insertion positions. Call-sites where that's necessary were
updated a year ago; but to ensure some type safety however, we'd like to
have all calls to getFirstNonPHI use the iterator-returning version.

This patch changes a bunch of call-sites calling getFirstNonPHI to use
getFirstNonPHIIt, which returns an iterator. All these call sites are
where it's obviously safe to fetch the iterator then dereference it. A
follow-up patch will contain less-obviously-safe changes.

We'll eventually deprecate and remove the instruction-pointer
getFirstNonPHI, but not before adding concise documentation of what
considerations are needed (very few).

---------

Co-authored-by: Stephen Tozer <Melamoto@gmail.com>

Note that the version of getValueProfDataFromInst that returns bool
has been "deprecated" since:

  commit 1e15371dd8843dfc52b9435afaa133997c1773d8
  Author: Mingming Liu <mingmingl@google.com>
  Date:   Mon Apr 1 15:14:49 2024 -0700

---------

Co-authored-by: Mingming Liu <minglotus6@gmail.com>

We can implicitly convert RemainingVDs to an ArrayRef.  Note that
RemainingVDs is of type SmallVector<InstrProfValueData, 24>.

The `BlockFrequency` class abstracts `uint64_t` frequency values. Use it
more consistently in various APIs and disable implicit conversion to
make usage more consistent and explicit.

- Use `BlockFrequency Freq` parameter for `setBlockFreq`,
`getProfileCountFromFreq` and `setBlockFreqAndScale` functions.
- Return `BlockFrequency` in `getEntryFreq()` functions.
- While on it change some `const BlockFrequency& Freq` parameters to
plain `BlockFreqency Freq`.
- Mark `BlockFrequency(uint64_t)` constructor as explicit.
- Add missing `BlockFrequency::operator!=`.
- Remove `uint64_t BlockFreqency::getMaxFrequency()`.
- Add `BlockFrequency BlockFrequency::max()` function.

Adding this prefix will indicate clearly that the compiler doesn't exit
when it hits this diagnostic. Searches for other non-fatal diagnostics
will also be able to find this diagnostic easily.

Differential Revision: https://reviews.llvm.org/D140085

This is part of a series of cleanup patches towards making BasicBlock::getInstList() private.

Differential Revision: https://reviews.llvm.org/D138877

Previously, we only checked for duplicate zero entries when merging a
MemOPSize table (see D92074), but a user recently provided a reproducer
demonstrating that other entries can also be duplicated. As demonstrated
by the test in this patch, PGOMemOPSizeOpt can potentially generate
invalid IR for non-zero, non-consecutive duplicate entries. This seems
to be a rare case, since the duplicate entry is often below the
threshold, but possible. This patch extends the existing warning to
check for any duplicate values in the table, both in the optimization
and in llvm-profdata.

Differential Revision: https://reviews.llvm.org/D136211

avoiding an assertion.

A BB with a nonzero count, whose successor blocks all have 0 counts, could
cause an assertion. Don't create any branch weights in this case.

Reviewed By: xur

Differential Revision: https://reviews.llvm.org/D134203