[NFC][LV] Use different braces in debug output

The analysis passes output function name encapsulated in `'` braces,
but LV uses `"`. Harmonizing this may help in creating an update script
for the LV

[NFC][LV] Use different braces in debug output

The analysis passes output function name encapsulated in `'` braces,
but LV uses `"`. Harmonizing this may help in creating an update script
for the LV costmodel test checks.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D121105

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[LoopVectorize] Support epilogue vectorisation of loops with reductions

isCandidateForEpilogueVectorization will currently return false for loops
which contain reductions. This patch removes this re

[LoopVectorize] Support epilogue vectorisation of loops with reductions

isCandidateForEpilogueVectorization will currently return false for loops
which contain reductions. This patch removes this restriction and makes
the following changes to support epilogue vectorisation with reductions:

- `fixReduction`: If fixReduction is being called during vectorisation of the
epilogue, the phi node it creates will need to additionally carry incoming
values from the middle block of the main loop.

- `createEpilogueVectorizedLoopSkeleton`: The incoming values of the phi
created by fixReduction are updated after the vec.epilog.iter.check block
is added. The phi is also moved to the preheader of the epilogue.

- `processLoop`: The start value of any VPReductionPHIRecipes are updated before
vectorising the epilogue loop. The getResumeInstr function added to the ILV
will return the resume instruction associated with the recurrence descriptor.

Reviewed By: sdesmalen

Differential Revision: https://reviews.llvm.org/D116928

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[LV] Legalize scalable VF hints

In the following loop:

void foo(int *a, int *b, int N) {
for (int i=0; i<N; ++i)
a[i + 4] = a[i] + b[i];
}

The loop dependence constrains the VF to a

[LV] Legalize scalable VF hints

In the following loop:

void foo(int *a, int *b, int N) {
for (int i=0; i<N; ++i)
a[i + 4] = a[i] + b[i];
}

The loop dependence constrains the VF to a maximum of (4, fixed), which
would mean using <4 x i32> as the vector type in vectorization.
Extending this to scalable vectorization, a VF of (4, scalable) implies
a vector type of <vscale x 4 x i32>. To determine if this is legal
vscale must be taken into account. For this example, unless
max(vscale)=1, it's unsafe to vectorize.

For SVE, the number of bits in an SVE register is architecturally
defined to be a multiple of 128 bits with a maximum of 2048 bits, thus
the maximum vscale is 16. In the loop above it is therefore unfeasible
to vectorize with SVE. However, in this loop:

void foo(int *a, int *b, int N) {
#pragma clang loop vectorize_width(X, scalable)
for (int i=0; i<N; ++i)
a[i + 32] = a[i] + b[i];
}

As long as max(vscale) multiplied by the number of lanes 'X' doesn't
exceed the dependence distance, it is safe to vectorize. For SVE a VF of
(2, scalable) is within this constraint, since a vector of <16 x 2 x 32>
will have no dependencies between lanes. For any number of lanes larger
than this it would be unsafe to vectorize.

This patch extends 'computeFeasibleMaxVF' to legalize scalable VFs
specified as loop hints, implementing the following behaviour:
* If the backend does not support scalable vectors, ignore the hint.
* If scalable vectorization is unfeasible given the loop
dependence, like in the first example above for SVE, then use a
fixed VF.
* Accept scalable VFs if it's safe to do so.
* Otherwise, clamp scalable VFs that exceed the maximum safe VF.

Reviewed By: sdesmalen, fhahn, david-arm

Differential Revision: https://reviews.llvm.org/D91718

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[LV] Disable epilogue vectorization for scalable VFs

Epilogue vectorization doesn't support scalable vectorization factors
yet, disable it for now.

Reviewed By: sdesmalen, bmahjour

Differential Re

[LV] Disable epilogue vectorization for scalable VFs

Epilogue vectorization doesn't support scalable vectorization factors
yet, disable it for now.

Reviewed By: sdesmalen, bmahjour

Differential Revision: https://reviews.llvm.org/D93063

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[LoopVectorize] Fix optimal-epilog-vectorization-limitations.ll test on non-debug build bots

Add "REQUIRES: asserts" as the test uses the "--debug-only" switch

Should fix the clang-with-thin-lto-ub

[LoopVectorize] Fix optimal-epilog-vectorization-limitations.ll test on non-debug build bots

Add "REQUIRES: asserts" as the test uses the "--debug-only" switch

Should fix the clang-with-thin-lto-ubuntu buildbot failure

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[LV] Epilogue Vectorization with Optimal Control Flow (Recommit)

This is yet another attempt at providing support for epilogue
vectorization following discussions raised in RFC http://llvm.1065342.n

[LV] Epilogue Vectorization with Optimal Control Flow (Recommit)

This is yet another attempt at providing support for epilogue
vectorization following discussions raised in RFC http://llvm.1065342.n5.nabble.com/llvm-dev-Proposal-RFC-Epilog-loop-vectorization-tt106322.html#none
and reviews D30247 and D88819.

Similar to D88819, this patch achieve epilogue vectorization by
executing a single vplan twice: once on the main loop and a second
time on the epilogue loop (using a different VF). However it's able
to handle more loops, and generates more optimal control flow for
cases where the trip count is too small to execute any code in vector
form.

Reviewed By: SjoerdMeijer

Differential Revision: https://reviews.llvm.org/D89566

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[LV] Epilogue Vectorization with Optimal Control Flow

This is yet another attempt at providing support for epilogue
vectorization following discussions raised in RFC http://llvm.1065342.n5.nabble.co

[LV] Epilogue Vectorization with Optimal Control Flow

This is yet another attempt at providing support for epilogue
vectorization following discussions raised in RFC http://llvm.1065342.n5.nabble.com/llvm-dev-Proposal-RFC-Epilog-loop-vectorization-tt106322.html#none
and reviews D30247 and D88819.

Similar to D88819, this patch achieve epilogue vectorization by
executing a single vplan twice: once on the main loop and a second
time on the epilogue loop (using a different VF). However it's able
to handle more loops, and generates more optimal control flow for
cases where the trip count is too small to execute any code in vector
form.

Reviewed By: SjoerdMeijer

Differential Revision: https://reviews.llvm.org/D89566

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