[all-commits] [llvm/llvm-project] 624498: [1/15][Clang][RISCV][NFC] Extract common utility t...

[Yueh-Ting (eop) Chen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 62449823476bf71c2510c174e387c9c99d219722
      https://github.com/llvm/llvm-project/commit/62449823476bf71c2510c174e387c9c99d219722
  Author: eopXD <yueh.ting.chen at gmail.com>
  Date:   2023-01-24 (Tue, 24 Jan 2023)

  Changed paths:
    M clang/include/clang/Support/RISCVVIntrinsicUtils.h
    M clang/lib/Sema/SemaRISCVVectorLookup.cpp
    M clang/lib/Support/RISCVVIntrinsicUtils.cpp
    M clang/utils/TableGen/RISCVVEmitter.cpp

  Log Message:
  -----------
  [1/15][Clang][RISCV][NFC] Extract common utility to RISCVVIntrinsicUtils

This is the 1st commit of a patch-set that aims to change the default policy
for RVV intrinsics from TAMU to TAMA.

The patch-set work towards the simplification proposal [0] of Nick
Knight. After this patch-set, all intrinsics operates under a general
assumption that the policy behavior is agnostic.

You may find that most of the patches are NFC patches. They subtly remove
implicit assumptions that entangles the codebase, making the singular patch
that contains functional change clear and obvious.

In [2/15], The attribute `Policy::IsPolicyNone` may give the mis-perception
that an RVV intrinsic may operate without any policy. However this is not the
case because the policy CSR-s (`vta` and `vma`) always affect an RVV
instruction's behavior, except that some instructions have policy always set
as agnostic (e.g. instructions with a mask destination register is always
tail agnostic).

Next, to perform the change from TAMU to TAMA, we need to first remove
`Policy::PolicyType::Omit`. [4/15] ~ [12/15] removes it with NFC patches step
by step. Without the patches, directly applying [14/15] to the existing codebase
will not work because there will be complicated logics that are scattered in
places that is hard to maintain.

[1/15], [3/15] are not related to the main goal of this patch-set, they were
clean-up along the way as I was going through the codebase. [13/15] is a
clean-up that was an oversight in D141198.

Finally, [14/15] performs the functional change this patch-set aims for. The
default policy is changed from TAMU to TAMA. This affects the masked version of
the intrinsics without a policy suffix. The masked-off operand is removed. Due
to the removal, masked version of `vid` and `viota` intrinsics are no longer
available for overloading.

[15/15] is a final commit to set data members of `Policy` as constants. Through
the refactoring the class `Policy` is now correct-by-construction.

The next patch-set will be to remove redundant intrinsics with a policy suffix
`_ta` and `_tama` intrinsics are redundant and will be removed. Other policy
suffix will be renamed to adapt to the general assumption that policy is
generally agnostic.

[0] https://gist.github.com/nick-knight/6cb0b74b351a25323dfb1821d3a269b9

Pull Request: riscv-non-isa/rvv-intrinsic-doc#186

Reviewed By: craig.topper, kito-cheng

Differential Revision: https://reviews.llvm.org/D141573