[RISCV] Xqci with Short Forward Branches (#161407)

This change implements support for the combination of Xqci and the Short
Forward Branch optimisation.

In particular, we want to prioritise `Branch+ALU` (short forward
branches) over the equivalent `ALU+CMov`, when the compared values are
both registers, and the selected values come from registers (as this is
what `PseudoCCMOVGPR` supports).

However, when expanding `PseudoCCMOVGPR` (i.e., `Branch+MV`), we instead
want to expand it to a conditional move (for code size reasons), so I
have added `RISCVExpandPseudo::expandCCOpToCMov` to try to do so. This
mostly works, except if `PseudoCCMOVGPR` is comparing against zero and
gets commuted - as can be seen in one example in `foo` in
`select-cc.ll`.

This change:
- updates the attributes used for the XQCI RUN lines for the select
tests.
- modifies the CodeGen patterns and predicates to prioritise selecting
the SFB Pseudo.
- adds CodeGen patterns for MVLTI/MVLTUI/MVGEI/MVGEUI with imm=zero, to
prioritise over the equivalent `Select_GPR_Using_CC_GPR` patterns for
rhs=X0.
- adds a hook to attempt to turn the predicated-mov Pseudo back into a
Conditional Move from Xqcicm (which matches the pseudo in terms of tied
register operands).

0 files changed, 0 insertions, 0 deletions