Changes

[ORC][examples] Remove ThinLtoJIT example after LLJITWithThinLTOSummaries landed in OrcV2Examples

The ThinLtoJIT example was aiming to utilize ThinLTO summaries and concurrency in ORC for speculative compilation. The latter is heavily dependent on asynchronous task scheduling which is probably done better out-of-tree with a mature library like Boost-ASIO. The pure utilization of ThinLTO summaries in ORC is demonstrated in OrcV2Examples/LLJITWithThinLTOSummaries.

[ORC][examples] Temporarily remove LLJITWithChildProcess until ORC TPC lands

This solves a phase ordering problem: OrcV2 remote process support depends on OrcV2 removable code, OrcV2 removable code depends on OrcV1 removal, OrcV1 removal depends on LLJITWithChildProcess migration, and LLJITWithChildProcess migration depends on OrcV2 TargetProcessControl support.

[ARM][LowOverheadLoops] Start insertion point

If possible, try not to move the start position earlier than it
already is.

Differential Revision: https://reviews.llvm.org/D88542

[ARM][LowOverheadLoops] Iteration count liveness

Before deciding to insert a [W|D]LSTP, check that defining LR with
the element count won't affect any other instructions that should be
taking the iteration count.

Differential Revision: https://reviews.llvm.org/D88549

[NFC] Iterate across an explicit list of scalable MVTs when driving setOperationAction.

Iterating across all of integer_scalable_vector_valuetypes seems
wasteful when there's only a handful we care about.

Also removes some rouge whitespace.

Differential Revision: https://reviews.llvm.org/D88552

[SVE][CodeGen] Legalisation of integer -> floating point conversions

Splitting the operand of a scalable [S|U]INT_TO_FP results in a
concat_vectors operation where the operands are unpacked FP
scalable vectors (e.g. nxv2f32).
This patch adds custom lowering of concat_vectors which
checks that the number of operands is 2, and isel patterns
to match concat_vectors of scalable FP types with uzp1.

Reviewed By: efriedma, paulwalker-arm

Differential Revision: https://reviews.llvm.org/D88033

[ARM][LowOverheadLoops] Adjust Start insertion.

Try to move the insertion point to become the terminator of the
block, usually the preheader.

Differential Revision: https://reviews.llvm.org/D88638

[SCEV] Prove implicaitons via AddRec start

If we know that some predicate is true for AddRec and an invariant
(w.r.t. this AddRec's loop), this fact is, in particular, true on the first
iteration. We can try to prove the facts we need using the start value.

The motivating example is proving things like
```
  isImpliedCondOperands(>=, X, 0, {X,+,-1}, 0}
```

Differential Revision: https://reviews.llvm.org/D88208
Reviewed By: reames

[mlir][Linalg] Fix ASAN bug

```
 LinalgTilingOptions &setTileSizes(ValueRange ts)
```
makes it all too easy to create stack-use-after-return errors.

In particular, c694588fc52a8845174fee06ad0bcfa338e87816 introduced one such issue.

Instead just take a copy in the lambda and be done with it.

[SVE][CodeGen] Lower scalable fp_extend & fp_round operations

This patch adds FP_EXTEND_MERGE_PASSTHRU & FP_ROUND_MERGE_PASSTHRU
ISD nodes, used to lower scalable vector fp_extend/fp_round operations.
fp_round has an additional argument, the 'trunc' flag, which is an integer of zero or one.

This also fixes a warning introduced by the new tests added to sve-split-fcvt.ll,
resulting from an implicit TypeSize -> uint64_t cast in SplitVecOp_FP_ROUND.

Reviewed By: sdesmalen, paulwalker-arm

Differential Revision: https://reviews.llvm.org/D88321

[CFGuard] Add address-taken IAT tables and delay-load support

This patch adds support for creating Guard Address-Taken IAT Entry Tables (.giats$y sections) in object files, matching the behavior of MSVC. These contain lists of address-taken imported functions, which are used by the linker to create the final GIATS table.
Additionally, if any DLLs are delay-loaded, the linker must look through the .giats tables and add the respective load thunks of address-taken imports to the GFIDS table, as these are also valid call targets.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D87544

[InstCombine] collectBitParts - use APInt directly to check for out of range bit shifts. NFCI.

[lldb] Skip the flakey part of TestStopHookScripted on Linux

This test seems to randomly fail on Linux machines. It's only one part of the
test failing randomly, so let's just skip it instead of reverting the whole
patch (again).

[libc++] Simplify how we re-export symbols from libc++abi

Instead of managing two copies of the symbol lists, reuse the same list
in libc++abi and libc++.

Differential Revision: https://reviews.llvm.org/D88623

[lldb] Add missing import for LLDB test decorators to TestStopHookScripted

This test wasn't using decorators before and was missing the import, so my
previous commit broke the test.

[NFC][ARM] LowOverheadLoop DEBUG statements

[LoopFlatten] Add a loop-flattening pass

This is a simple pass that flattens nested loops.  The intention is to optimise
loop nests like this, which together access an array linearly:

  for (int i = 0; i < N; ++i)
    for (int j = 0; j < M; ++j)
      f(A[i*M+j]);

into one loop:

  for (int i = 0; i < (N*M); ++i)
    f(A[i]);

It can also flatten loops where the induction variables are not used in the
loop. This can help with codesize and runtime, especially on simple cpus
without advanced branch prediction.

This is only worth flattening if the induction variables are only used in an
expression like i*M+j. If they had any other uses, we would have to insert a
div/mod to reconstruct the original values, so this wouldn't be profitable.

This partially fixes PR40581 as this pass triggers on one of the two cases. I
will follow up on this to learn LoopFlatten a few more (small) tricks. Please
note that LoopFlatten is not yet enabled by default.

Patch by Oliver Stannard, with minor tweaks from Dave Green and myself.

Differential Revision: https://reviews.llvm.org/D42365

[gn build] Port d53b4bee0cc

[Archive] Don't throw away errors for malformed archive members

When adding an archive member with a problem, e.g. a new bitcode with an
old archiver, containing an unsupported attribute, or an ELF file with a
malformed symbol table, the archiver would throw away the error and
simply add the member to the archive without any symbol entries. This
meant that the resultant archive could be silently unusable when not
using --whole-archive, and result in unexpected undefined symbols.

This change fixes this issue by addressing two FIXMEs and only throwing
away not-an-object errors. However, this meant that some LLD tests which
didn't need symbol tables and were using invalid members deliberately to
test the linker's malformed input handling no longer worked, so this
patch also stops the archiver from looking for symbols in an object if
it doesn't require a symbol table, and updates the tests accordingly.

Differential Revision: https://reviews.llvm.org/D88288

Reviewed by: grimar, rupprecht, MaskRay

[SVE][CodeGen] Replace use of TypeSize operator< in GlobalMerge::doMerge

We don't support global variables with scalable vector types so I've
changed the code to compare the fixed sizes instead.

Differential Revision: https://reviews.llvm.org/D88564