[PATCH] D67397: [RISCV] Add MachineInstr immediate verification

[Luís Marques via Phabricator via llvm-commits]

luismarques created this revision.
luismarques added reviewers: asb, lenary.
Herald added subscribers: llvm-commits, pzheng, s.egerton, Jim, benna, psnobl, jocewei, PkmX, rkruppe, the_o, brucehoult, MartinMosbeck, rogfer01, edward-jones, zzheng, MaskRay, jrtc27, shiva0217, kito-cheng, niosHD, sabuasal, apazos, simoncook, johnrusso, rbar, hiraditya.
Herald added a project: LLVM.

This patch implements the `TargetInstrInfo::verifyInstruction` hook for RISC-V. Currently the hook verifies the machine instruction's immediate operands, to check if the immediates are within the expected bounds. Currently invalid immediates are not detected except when doing assembly parsing, so they are silently emitted (including being truncated when emitting object code).

The bounds information is specified in tablegen by using the `OperandType` definition, which sets the `MCOperandInfo`'s `OperandType` field. Several RISC-V-specific immediate operand types were created, which extend the `MCInstrDesc`'s `OperandType` `enum`.

To have the hook called with `llc` pass it the `-verify-machineinstrs` option. For Clang add the cmake build config `-DLLVM_ENABLE_EXPENSIVE_CHECKS=True`, or temporarily patch `TargetPassConfig::addVerifyPass`.

Review concerns:

- The patch adds immediate operand type checks that cover at least the base ISA. There are several other operand types for the C extension and one type for the F/D extensions that were left out of this initial patch because they introduced further design concerns that I felt were best evaluated separately.

- Invalid register classes (e.g. passing a GPR register where a GPRC is expected) are already caught, so were not included.

- This design makes the more abstract `MachineInstr` verification depend on MC layer definitions, which arguably is not the cleanest design, but is in line with how things are done in other parts of the target and LLVM in general.

- There is some duplication of logic already present in the `MCOperandPredicate`s. Since the `MachineInstr` and `MCInstr` notions of immediates are fundamentally different, this is currently necessary.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D67397

Files:
  llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCTargetDesc.cpp
  llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
  llvm/lib/Target/RISCV/RISCVInstrInfo.h
  llvm/lib/Target/RISCV/RISCVInstrInfo.td
  llvm/lib/Target/RISCV/RISCVSubtarget.cpp
  llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.h

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