This PR provides implementation of the basic codegen infra such as
TargetFrameLowering, MCInstLower,
AsmPrinter, RegisterInfo, InstructionInfo, TargetLowering,
SelectionDAGISel.
Migrated from https://reviews.llvm.org/D145658
This will make it easy for callers to see issues with and fix up calls
to createTargetMachine after a future change to the params of
TargetMachine.
This matches other nearby enums.
For downstream users, this should be a fairly straightforward
replacement,
e.g. s/CodeGenOpt::Aggressive/CodeGenOptLevel::Aggressive
or s/CGFT_/CodeGenFileType::
Add Xtensa MCTargetDesc stub. Add XtensaTargetMachine and XtensaTargetInfo.
Modify llib/Target/LLVMBuild.txt. Now Xtensa target could be builded as EXPERIMENTAL.
Differential Revision: https://reviews.llvm.org/D64829
