- _Float16 is now accepted by Clang.

- The half IR type is fully handled by the backend.

- These values are passed in FP registers and converted to/from float around
  each operation.

- Compiler-rt conversion functions are now built for s390x including the missing
  extendhfdf2 which was added.

Fixes #50374

DenseSet, SmallPtrSet, SmallSet, SetVector, and StringSet recently
gained C++23-style insert_range.  This patch replaces:

  Dest.insert(Src.begin(), Src.end());

with:

  Dest.insert_range(Src);

This patch does not touch custom begin like succ_begin for now.

This pr includes fixes for original pr##116642.
Implementation for __builtin_setjmp and __builtin_longjmp for SystemZ..

This reverts commit 030bbc92a705758f1131fb29cab5be6d6a27dd1f.

Implementation for __builtin_setjmp and __builtin_longjmp for SystemZ.

SystemZRegisterInfo::shouldCoalesce() has to be able to handle an undef
source.

The SystemZ implementation of shouldCoalesce() is merely a workaround
for the fact that regalloc can run out of registers when extending 128-bit
intervals with subreg (GPR64/GPR32) COPYs. 

This patch adds more freedom to the coalescer as it now only checks that
the subreg interval is local to MBB and does not have too many physreg
clobbers.

Differential Revision: https://reviews.llvm.org/D148613

A rare case where coalescing resulted in a hh32 (high32 of high64 of vector
register) subreg usage caused getSubReg() to fail as the vector reg does not
have that subreg in its subregs list, but rather h32 which was expected to
also act as hh32. See link below for the discussion when solving this.

Patch By: critson

Reviewed By: uweigand

Fixes: https://github.com/llvm/llvm-project/issues/61390