Introduce m_scev_AffineAddRec to match affine AddRecs, a class_match for
SCEVConstant, and demonstrate their utility in LSR and SCEV. While at
it, rename m_Specific to m_scev_Specific for clarity.

This patch adds preprocessor macros when Zicfilp CFI is enabled. To be
specific:

+ `#define __riscv_landing_pad 1` when `-fcf-protection=[full|branch]`
+ `#define __riscv_landing_pad_unlabeled 1` when
`-fcf-protection=[full|branch] -mcf-branch-label-scheme=unlabeled`

The macros are proposed in riscv-non-isa/riscv-c-api-doc#76 , and the
CLI flags are from riscv-non-isa/riscv-toolchain-conventions#54.

This completes the set of maths builtins.

No attempt to vectorize or optimize this code. The implementation is
licensed to SunPro so will probably need to be replaced at some point in
the future anyway. Calls to other builtins have been replaced with the
CLC equivalents, and some bit-hacking was replaced with the fabs
builtin.

Have the test accept use of the toolchain assembler instead of `-cc1as`
as some targets, such as AIX, do not use `-cc1as`.

Not sure if this did anything for compile time or not.

This sorts ConstantData to the low values, so we can perform
a hasUseList check in a single compare instead of requiring 2
compares plus an and for the range check.

We need a place to destroy the temporaries created for call arguments.

When reducing unrolled parts, explicitly check for min/max reductions
using the function RecurrenceDescriptor::isMinMaxRecurrenceKind. Only if
the reduction is not min/max reduction, call
RecurrenceDescriptor::getOpcode() to handle other cases via CreateBinOp.

Based on https://github.com/llvm/llvm-project/pull/140242
Related to https://github.com/llvm/llvm-project/pull/118393

The offset we return for them are just indices, so we can use a vector
here.