[NFC] Move some asserts out of Expensive Checks

This was done by reviewer's request, but in fact without them we
skip very nasty bugs. Unless it is a REAL problem, I'd keep them
in default setup.

[SimpleLoopUnswitch] Temorarily switch off simple-loop-unswitch-inject-invariant-conditions. PR60736

It caused an assertion failure, not sure induced or introduced. Disabling
to investigate it. See

[SimpleLoopUnswitch] Temorarily switch off simple-loop-unswitch-inject-invariant-conditions. PR60736

It caused an assertion failure, not sure induced or introduced. Disabling
to investigate it. See details at https://github.com/llvm/llvm-project/issues/60736

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[SimpleLoopUnswitch] Inject loop-invariant conditions and unswitch them when it's profitable

Based on https://discourse.llvm.org/t/rfc-inject-invariant-conditions-to-loops-to-enable-unswitching-and-

[SimpleLoopUnswitch] Inject loop-invariant conditions and unswitch them when it's profitable

Based on https://discourse.llvm.org/t/rfc-inject-invariant-conditions-to-loops-to-enable-unswitching-and-constraint-elimination

This transform attempts to handle the following loop:
```
for (...) {
x = <some variant>
if (x <u C1) {} else break;
if (x <u C2) {} else break;
}
```
Here `x` is some loop-variant value, and `C1` and `C2` are loop invariants.
As we see, this loop has no invariant checks we can unswitch on. However, there is an
invariant condition that can make the second check redundant. Specifically, it is `C1 <=u C2`.
We can modify this code in the following way:
```
for (...) {
x = <some variant>
if (x <u C1) {} else break;
if (C1 <=u C2) {
/* no check is required */
}
else {
// do the check normally
if (x <u C2) {} else break;
}
}
```
Now we have an invariant condition `C1 <=u C2` and can unswitch on it.

This patch introduces the basic version of this transform, with some limitations,
all of them seem liftable (but needs more work & testing):
- All checks are `ult` condition;
- All branches in question stay in loop if the said condition is true and leave it otherwise;
- All in-loop branches are hot enough;

There is also a room for improvement cost model. So far we evalutate the cost of
unswitching this newly injected invariant branch the same as if we would unswitch
on 2nd condition, which is not exactly precise (but also not grossly wrong).

Differential Revision: https://reviews.llvm.org/D136233
Reviewed By: skatkov

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Move from llvm::makeArrayRef to ArrayRef deduction guides - llvm/ part

Use deduction guides instead of helper functions.

The only non-automatic changes have been:

1. ArrayRef(some_uint8_pointer, 0

Move from llvm::makeArrayRef to ArrayRef deduction guides - llvm/ part

Use deduction guides instead of helper functions.

The only non-automatic changes have been:

1. ArrayRef(some_uint8_pointer, 0) needs to be changed into ArrayRef(some_uint8_pointer, (size_t)0) to avoid an ambiguous call with ArrayRef((uint8_t*), (uint8_t*))
2. CVSymbol sym(makeArrayRef(symStorage)); needed to be rewritten as CVSymbol sym{ArrayRef(symStorage)}; otherwise the compiler is confused and thinks we have a (bad) function prototype. There was a few similar situation across the codebase.
3. ADL doesn't seem to work the same for deduction-guides and functions, so at some point the llvm namespace must be explicitly stated.
4. The "reference mode" of makeArrayRef(ArrayRef<T> &) that acts as no-op is not supported (a constructor cannot achieve that).

Per reviewers' comment, some useless makeArrayRef have been removed in the process.

This is a follow-up to https://reviews.llvm.org/D140896 that introduced
the deduction guides.

Differential Revision: https://reviews.llvm.org/D140955

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[SimpleLoopUnswitch] Perform poison query before transform

I think this doesn't make any difference right now, but once
we take into account that branch on undef is UB in
programUndefinedIfUndefOrPo

[SimpleLoopUnswitch] Perform poison query before transform

I think this doesn't make any difference right now, but once
we take into account that branch on undef is UB in
programUndefinedIfUndefOrPoison() the new position of the branch
would imply that the condition can't be poison, which would
defeat the purpose of the freeze insertion here. We need to
perform the check before the branch is moved.

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[NFC] Rename Instruction::insertAt() to Instruction::insertInto(), to be consistent with BasicBlock::insertInto()

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

[Transforms/Scalar] llvm::Optional => std::optional

[NFC] Cleanup: Replaces BB->getInstList().insert() with I->insertAt().

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

Differential Revision: https://r

[NFC] Cleanup: Replaces BB->getInstList().insert() with I->insertAt().

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

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

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[Transforms] Use std::nullopt instead of None (NFC)

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount

[Transforms] Use std::nullopt instead of None (NFC)

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.

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

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[NFC] Cleanup: Replaces BB->getInstList().splice() with BB->splice().

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

Differential Revision: https://re

[NFC] Cleanup: Replaces BB->getInstList().splice() with BB->splice().

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

Differential Revision: https://reviews.llvm.org/D138979

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[Scalar] Use std::optional in SimpleLoopUnswitch.cpp (NFC)

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

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasval

[Scalar] Use std::optional in SimpleLoopUnswitch.cpp (NFC)

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

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Don't use Optional::getPointer (NFC)

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.

Don't use Optional::getPointer (NFC)

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

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[SimpleLoopUnswitch] Forget SCEVs for replaced phis.

Forget SCEVs based on exit phis in case SCEV looked through the phi.
After unswitching, it may not be possible to look through the phi due to
it

[SimpleLoopUnswitch] Forget SCEVs for replaced phis.

Forget SCEVs based on exit phis in case SCEV looked through the phi.
After unswitching, it may not be possible to look through the phi due to
it having multiple incoming values, so it needs to be re-computed.

Fixes #58868

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[SimpleLoopUnswitch] Skip trivial selects in guards conditions unswitch candidates

We do this for conditional branches, but not for guards for some reason.

Fixes pr58666.

Differential Revision: ht

[SimpleLoopUnswitch] Skip trivial selects in guards conditions unswitch candidates

We do this for conditional branches, but not for guards for some reason.

Fixes pr58666.

Differential Revision: https://reviews.llvm.org/D137249

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[SimpleLoopUnswitch] Forget block & loop dispos during trivial unswitch.

Unswitching adjusts the CFG in ways that may invalidate cached loop
dispositions. Clear all cached block and loop disposition

[SimpleLoopUnswitch] Forget block & loop dispos during trivial unswitch.

Unswitching adjusts the CFG in ways that may invalidate cached loop
dispositions. Clear all cached block and loop dispositions during
trivial unswitching. The same is already done for non-trivial
unswitching.

Fixes #58751.

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[SimpleLoopUnswitch] Forget block and loop dispositions.

Also invalidate block and loop dispositions during non-trivial
unswitching.

Fixes #58564.

[NFC] Reuse NonTrivialUnswitchCandidate instead of std::pair

[NFC] Perform all legality checks for non-trivial unswitch in one function

They have been scattered over the code. For better structuring, perform
them in one place. Potential CT drop is possible be

[NFC] Perform all legality checks for non-trivial unswitch in one function

They have been scattered over the code. For better structuring, perform
them in one place. Potential CT drop is possible because we collect exit
blocks twice, but it's small price to pay for much better code structure.

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[SimpleLoopUnswitch][NFC] Separate legality checks from cost computation

These are semantically two different stages, but were entwined in the
old implementation. Now cost computation does not do le

[SimpleLoopUnswitch][NFC] Separate legality checks from cost computation

These are semantically two different stages, but were entwined in the
old implementation. Now cost computation does not do legality checks,
and they all are done beforehead.

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[NFC] Factor out computation of best unswitch cost candidate

Split out a major peice of this method to make code more readable.

[NFC] Factor out collection of unswitch candidate to a separate function

Just to make the code more structured and easier to understand.

[NFC] Refine API in SimpleLoopUnswitch: add missing const notions

[SimpleLoopUnswitch] Clear dispos in deleteDeadBlocksFromLoop.

SimpleLoopUnswitch may remove blocks from loops. Clear block and loop
dispositions in that case, to clean up invalid entries in the cac

[SimpleLoopUnswitch] Clear dispos in deleteDeadBlocksFromLoop.

SimpleLoopUnswitch may remove blocks from loops. Clear block and loop
dispositions in that case, to clean up invalid entries in the cache.

Fixes #58158.

Fixes #58159.

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[SimpleLoopUnswitch] Clear block and loop dispos after destroying loop.

SimpleLoopUnswitch may remove loops. Clear block and loop dispositions,
to clean up invalid entries in the cache.

Fixes #5813

[SimpleLoopUnswitch] Clear block and loop dispos after destroying loop.

SimpleLoopUnswitch may remove loops. Clear block and loop dispositions,
to clean up invalid entries in the cache.

Fixes #58136.

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[SimpleLoopUnswitch] Skip non-trivial unswitching of cold functions

In the current main branch, all cold loops will not be applied non-trivial unswitch. As reported in D129599, skipping these cold l

[SimpleLoopUnswitch] Skip non-trivial unswitching of cold functions

In the current main branch, all cold loops will not be applied non-trivial unswitch. As reported in D129599, skipping these cold loops will incur regression in SPEC benchmark.
Thus, instead of skipping cold loops, now only skipping loops in cold functions.

Reviewed By: alexgatea, aeubanks

Differential Revision: https://reviews.llvm.org/D133275

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