This allows SDNodes to be validated against their expected type profiles
and reduces the number of changes required to add a new node.

I had to split `VSHUF4I` into two variants (`VSHUF4I` and `VSHUF4I_D`)
since `loongarch_vshuf4i` and `loongarch_vshuf4i_d` have different
number of operands, and this prevented the node from being imported.

There is just one node that currently fails validation, see
`LoongArchSelectionDAGInfo::verifyTargetNode()`.

Part of #119709.

Pull Request: https://github.com/llvm/llvm-project/pull/168129

Currently LibcallLoweringInfo is defined inside of TargetLowering,
which is owned by the subtarget. Pass in the subtarget so we can
construct LibcallLoweringInfo with the subtarget. This is a temporary
step that should be revertable in the future, after LibcallLoweringInfo
is moved out of TargetLowering.

This patch introduces a new virtual method
`TargetInstrInfo::isSafeToMove()` to allow backends to control whether a
machine instruction can be safely moved by optimization passes.

The `BranchFolder` pass now respects this hook when hoisting common
code. By default, all instructions are considered safe to to move.

For LoongArch, `isSafeToMove()` is overridden to prevent
relocation-related instruction sequences (e.g. PC-relative addressing
and calls) from being broken by instruction motion. Correspondingly,
`isSchedulingBoundary()` is updated to reuse this logic for consistency.

Relands #163725

Reverts llvm/llvm-project#163725

This is directly available in TargetInstrInfo

TargetInstrInfo now directly holds a reference to TargetRegisterInfo
and does not need TRI passed in anywhere.

Both conceptually belong to the same subtarget, so it should not
be necessary to pass in the context TargetRegisterInfo to any
TargetInstrInfo member. Add this reference so those superfluous
arguments can be removed.

Most targets placed their TargetRegisterInfo as a member
in TargetInstrInfo. A few had this owned by the TargetSubtargetInfo,
so unify all targets to look the same.

After overriding `TargetTransformInfo::enableMemCmpExpansion` in this
commit, `MergeICmps` and `ExpandMemCmp` passes will be enabled on
LoongArch.

This patch introduces a new virtual method
`TargetInstrInfo::isSafeToMove()` to allow backends to control whether a
machine instruction can be safely moved by optimization passes.

The `BranchFolder` pass now respects this hook when hoisting common
code. By default, all instructions are considered safe to to move.

For LoongArch, `isSafeToMove()` is overridden to prevent
relocation-related instruction sequences (e.g. PC-relative addressing
and calls) from being broken by instruction motion. Correspondingly,
`isSchedulingBoundary()` is updated to reuse this logic for consistency.

Fixes #163681

Add option `loongarch-enable-sink-fold` to enable sink-fold and set
`true` as default. This pass can fold `addi+load/store` to a single
`load/store` with offset.