Deleting a basic block removes all references from jump tables, which
is O(n). When freeing a MachineFunction, all basic blocks are deleted
before the jump tables, causing O(n^2) runtime. Fix this by deallocating
the jump table first.

Test case generator:

    import sys

    n = int(sys.argv[1])
    print("define void @f(i64 %c, ptr %p) {")
    print("  switch i64 %c, label %d [")
    for i in range(n):
        print(f"    i64 {i}, label %h{i}")
    print(f"  ]")
    for i in range(n):
        print(f'h{i}:')
        print(f'  store i64 {i*i}, ptr %p')
        print(f'  ret void')
    print('d:')
    print('  ret void')
    print('}')

Improvement at 5000 entries:

    Benchmark 1: ./llc.pre -filetype=obj -O0 <switch5k.bc
      Time (mean ± σ):      49.7 ms ±   1.0 ms
      Range (min … max):    48.0 ms …  52.1 ms    57 runs

    Benchmark 2: ./llc.post -filetype=obj -O0 <switch5k.bc
      Time (mean ± σ):      39.4 ms ±   0.8 ms
      Range (min … max):    37.1 ms …  41.1 ms    72 runs

    Summary
      ./llc.post -filetype=obj -O0 <switch5k.bc ran
        1.26 ± 0.04 times faster than ./llc.pre -filetype=obj -O0 <switch5k.bc

Improvement at 20000 entries:

    Benchmark 1: ./llc.pre -filetype=obj -O0 <switch20k.bc
      Time (mean ± σ):     281.7 ms ±   1.0 ms
      Range (min … max):   280.2 ms … 283.0 ms    10 runs

    Benchmark 2: ./llc.post -filetype=obj -O0 <switch20k.bc
      Time (mean ± σ):     123.9 ms ±   1.5 ms
      Range (min … max):   121.4 ms … 129.2 ms    23 runs

    Summary
      ./llc.post -filetype=obj -O0 <switch20k.bc ran
        2.27 ± 0.03 times faster than ./llc.pre -filetype=obj -O0 <switch20k.bc

Pull Request: https://github.com/llvm/llvm-project/pull/144108

Add per-property has<Prop>/set<Prop>/reset<Prop> functions to
MachineFunctionProperties.

Targets are required to define this, it is not optional. Make the method
pure virtual to enforce this

The LiveDebugValues pass and the instruction selector (which calls
salvageCopySSA) need to be consistent on what they consider a copy
instruction. With https://github.com/llvm/llvm-project/pull/75184, the
definition of what a copy instruction is was narrowed for AArch64 to
exclude a w->x ORR and treat it as a zero-extend rather than a copy

However, to make sure LiveDebugValues still treats a w->x ORR as a copy,
the new function, isCopyLikeInstr was created. We need to make sure that
salvageCopySSA also calls that function.

This patch addresses this mismatch.

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>

https://discourse.llvm.org/t/rfc-profile-guided-static-data-partitioning/83744
proposes to partition static data sections.

This patch introduces a codegen pass. This patch produces jump table
hotness in the in-memory states (machine jump table info and entries).
Target-lowering and asm-printer consume the states and produce `.hot`
section suffix. The follow up PR
https://github.com/llvm/llvm-project/pull/122215 implements such
changes.

---------

Co-authored-by: Ellis Hoag <ellis.sparky.hoag@gmail.com>

Fixes the "use after poison" issue introduced by #121516 (see
<https://github.com/llvm/llvm-project/pull/121516#issuecomment-2585912395>).

The root cause of this issue is that #121516 introduced "Called Global"
information for call instructions modeling how "Call Site" info is
stored in the machine function, HOWEVER it didn't copy the
copy/move/erase operations for call site information.

The fix is to rename and update the existing copy/move/erase functions
so they also take care of Called Global info.

Try to use DiagnosticInfo if every register in the class is reserved
by forcing assignment to a reserved register. Also reduces the number
of redundant errors emitted, particularly with fast.

This is still broken in the case of undef uses. There are additional
complications in greedy and fast, so leave it for a separate fix.