[Exegesis][RISCV] Skip some of the tests under expensive checks
Under expensive checks, some of the tests will fail to pass the
MachineVerifier. It's because right after a snippet is generated, its VL
operand (if it's a register) is assigned a physical register. While
we'll replace it with virtual register in RISCVExegesisPreprocessing,
it's technically violating RISCVInstrInfo's validation rule.
Under normal circumstances, this won't trigger a MachineVerifier failure
because the codegen pipeline doesn't validate the code until the very
end -- which is not the case under EXPENSIVE_CHECKS where
MachineVerifierPass is sprinkled here and there.
This is really caused by the fact that RISCV exegesis has an odd
"codegen" Pass pipeline. And I don't have a good solution yet, so I'm
surpressing these tests under EXPENSIVE_CHECKS.
[Exegesis][RISCV] Add initial RVV support (#128767)
This patch adds initial vector extension support to RISC-V's exegesis.
The strategy here is to enumerate all RVV _pseudo_ opcodes as their MC
opcode counterparts are kind of useless under this circumstance. We also
enumerate all possible VTYPE operands in each CodeTemplate
configuration. Various of MachineFunction Passes are used for post
processing the snippets, like inserting VSETVLI instructions.
See https://llvm.org/devmtg/2024-10/slides/techtalk/Hsu-RVV-Exegesis.pdf
for more technical details.
