[RISCV] Add SiFive sf.vqmacc tests to vmv-copy.mir. NFC

[topperc]

The vqmaccu.2x8x2 test is currently being miscompiled. We need to use a whole register move instead of vmv.v.v. The input has VL elements with EEW=8 EMUL=4. The output has VL/4 elements with EEW=32 EMUL=4. We can't use the original VL a vmv.v.v.

[github-actions]

⚠️ undef deprecator found issues in your code. ⚠️

You can test this locally with the following command:

git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef[^a-zA-Z0-9_-]|UndefValue::get)' 1937a36209bc5f3636e7c98a1638ee9f082b4d2b 67f1464b49f91af07e19df5c48f8d91aa3207b2e

The following files introduce new uses of undef:

• llvm/test/CodeGen/RISCV/rvv/vmv-copy.mir

Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields undef. You should use poison values for placeholders instead.

In tests, avoid using undef and having tests that trigger undefined behavior. If you need an operand with some unimportant value, you can add a new argument to the function and use that instead.

For example, this is considered a bad practice:

define void @fn() {
  ...
  br i1 undef, ...
}

Please use the following instead:

define void @fn(i1 %cond) {
  ...
  br i1 %cond, ...
}

Please refer to the Undefined Behavior Manual for more information.

[wangpc-pp]

LGTM.

[preames]

LGTM