[RISCV] Rematerialize vmv.s.x and vfmv.s.f (#108012)

Continuing with #107993 and #108007, this handles the last of the main
rematerializable vector instructions.

There's an extra spill in one of the test cases, but it's likely noise
from the spill weights and isn't an issue in practice.

Author: lukel97

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -172,6 +172,8 @@ bool RISCVInstrInfo::isReallyTriviallyReMaterializable(
   case RISCV::VMV_V_X:
   case RISCV::VFMV_V_F:
   case RISCV::VMV_V_I:
+  case RISCV::VMV_S_X:
+  case RISCV::VFMV_S_F:
   case RISCV::VID_V:
     if (MI.getOperand(1).isUndef() &&
         /* After RISCVInsertVSETVLI most pseudos will have implicit uses on vl

llvm/lib/Target/RISCV/RISCVInstrInfoVPseudos.td

@@ -6764,7 +6764,7 @@ let mayLoad = 0, mayStore = 0, hasSideEffects = 0 in {
     Pseudo<(outs GPR:$rd), (ins VR:$rs2, ixlenimm:$sew), []>,
     Sched<[WriteVMovXS, ReadVMovXS]>,
     RISCVVPseudo;
-  let HasVLOp = 1, HasSEWOp = 1, BaseInstr = VMV_S_X,
+  let HasVLOp = 1, HasSEWOp = 1, BaseInstr = VMV_S_X, isReMaterializable = 1,
       Constraints = "$rd = $rs1" in
   def PseudoVMV_S_X: Pseudo<(outs VR:$rd),
                             (ins VR:$rs1, GPR:$rs2, AVL:$vl, ixlenimm:$sew),
@@ -6787,7 +6787,7 @@ let mayLoad = 0, mayStore = 0, hasSideEffects = 0 in {
              (ins VR:$rs2, ixlenimm:$sew), []>,
       Sched<[WriteVMovFS, ReadVMovFS]>,
       RISCVVPseudo;
-    let HasVLOp = 1, HasSEWOp = 1, BaseInstr = VFMV_S_F,
+    let HasVLOp = 1, HasSEWOp = 1, BaseInstr = VFMV_S_F, isReMaterializable = 1,
         Constraints = "$rd = $rs1" in
     def "PseudoVFMV_S_" # f.FX :
       Pseudo<(outs VR:$rd),