Add support for remaining pseudos in RISCVVLOptimizer

[lukel97]

Based off this list by @mikhailramalho in #146692 (comment)_, there are a few remaining pseudos that we could potentially support pending whether or not it's correct to reduce their VL:

• VFCLASS_V
• VFMV_F_S
• VFMV_S_F
• VMADC_VIM
• VMADC_VVM
• VMADC_VXM
• VMSBC_VVM
• VMSBC_VXM
• VMV_S_X
• VMV_X_S
• VRGATHEREI16_VV
• VRGATHER_VI
• VRGATHER_VV
• VRGATHER_VX
• VSBC_VVM
• VSBC_VXM
• VANDN_VX
• VANDN_VV
• VBREV_V
• VBREV8_V
• VREV8_V
• VCLZ_V
• VCPOP_V
• VCTZ_V
• VCLMUL_VV
• VCLMUL_VX
• VCLMULH_VV
• VCLMULH_VX
• VROR_VI
• VROR_VX
• VROR_VV
• VROL_VX
• VROL_VV

Once we're happy that we support everything we can and have tests, we should remove isSupportedInstr and replace it with RISCVII::elementsDependOnVL

[llvmbot]

@llvm/issue-subscribers-backend-risc-v

Author: Luke Lau (lukel97)

Based off this list by @mikhailramalho in https://github.com//issues/146692#issuecomment-3028026599_, there are a few remaining pseudos that we could potentially support pending whether or not it's correct to reduce their VL:

VFCLASS_V
VFMV_F_S
VFMV_S_F
VFREC7_V
VMADC_VIM
VMADC_VVM
VMADC_VXM
VMSBC_VVM
VMSBC_VXM
VMV1R_V
VMV2R_V
VMV4R_V
VMV8R_V
VMV_S_X
VMV_X_S
VRGATHEREI16_VV
VRGATHER_VI
VRGATHER_VV
VRGATHER_VX
VSBC_VVM
VSBC_VXM

Once we're happy that we support everything we can and have tests, we should remove isSupportedInstr and replace it with RISCVII::elementsDependOnVL

[mikhailramalho]

Once #153234 lands, only vfmv and vmv will remain, but landing those will require extra work to prevent regressions on SPEC, as I mentioned in #149562