To finalise the "RemoveDIs" work removing debug intrinsics, we're
updating call sites that insert instructions to use iterators instead.
This set of changes are those where it's not immediately obvious that
just calling getIterator to fetch an iterator is correct, and one or two
places where more than one line needs to change.

Overall the same rule holds though: iterators generated for the start of
a block such as getFirstNonPHIIt need to be passed into insert/move
methods without being unwrapped/rewrapped, everything else can use
getIterator.

When sinking a store, preserve common metadata present on stores on both
sides of the diamond.

PR: https://github.com/llvm/llvm-project/pull/116382

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.

This pass isn't used anywhere and thus isn't tested anywhere. Because of
these reasons, remove it.

Continuing the patch series to get rid of debug intrinsics [0], instruction
insertion needs to be done with iterators rather than instruction pointers,
so that we can communicate information in the iterator class. This patch
adds an iterator-taking insertBefore method and converts various call sites
to take iterators. These are all sites where such debug-info needs to be
preserved so that a stage2 clang can be built identically; it's likely that
many more will need to be changed in the future.

At this stage, this is just changing the spelling of a few operations,
which will eventually become signifiant once the debug-info bearing
iterator is used.

[0] https://discourse.llvm.org/t/rfc-instruction-api-changes-needed-to-eliminate-debug-intrinsics-from-ir/68939

Differential Revision: https://reviews.llvm.org/D152537

Since memory does not have an intrinsic type, we do not need to require value type matching on stores in order to sink them. To facilitate that, this patch finds stores which are sinkable, but have conflicting types, and bitcasts the ValueOperand so they are easily sinkable into a PHINode. Rather than doing fancy analysis to optimally insert the bitcast, we always insert right before the relevant store in the diamond branch. The assumption is that later passes (e.g. GVN, SimplifyCFG) will clean up bitcasts as needed.

Differential Revision: https://reviews.llvm.org/D147348

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D144365

Reapply with a fix for a failing debuginfo assignment tracking test.

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Allow sinking stores where both operands are the same, don't require
them to have an identical GEP in each block.

This came up when migrating tests to opaque pointers, where
zero-index GEPs are omitted.

I missed a test failure in the DebugInfo directory.

This reverts commit 2c15b9d9e1a898cfd849db81b36d278eac3ef24e.
This reverts commit fb435e1cb5842e1437436e9e7378dfc4106fdad8.

Allow sinking stores where both operands are the same, don't require
them to have an identical GEP in each block.

This came up when migrating tests to opaque pointers, where
zero-index GEPs are omitted.