Rebase, carry over the EEW check added in llvm#101152

Since we don't have access to the MVTs, we can also do the same thing by checking the VLMAXs are the same (i.e. the sew/lmul ratio)

Author: lukel97

llvm/lib/Target/RISCV/RISCVVectorPeephole.cpp

@@ -373,6 +373,12 @@ lookupActiveElementsAffectsResult(const MachineInstr &MI) {
   return Info->ActiveElementsAffectResult;
 }
 
+static unsigned getSEWLMULRatio(const MachineInstr &MI) {
+  RISCVII::VLMUL LMUL = RISCVII::getLMul(MI.getDesc().TSFlags);
+  unsigned Log2SEW = MI.getOperand(RISCVII::getSEWOpNum(MI.getDesc())).getImm();
+  return RISCVVType::getSEWLMULRatio(1 << Log2SEW, LMUL);
+}
+
 /// If a PseudoVMV_V_V is the only user of its input, fold its passthru and VL
 /// into it.
 ///
@@ -399,6 +405,10 @@ bool RISCVVectorPeephole::foldVMV_V_V(MachineInstr &MI) {
       !RISCVII::hasVecPolicyOp(Src->getDesc().TSFlags))
     return false;
 
+  // Src needs to have the same VLMAX as MI
+  if (getSEWLMULRatio(MI) != getSEWLMULRatio(*Src))
+    return false;
+
   // Src needs to have the same passthru as VMV_V_V
   if (Src->getOperand(1).getReg() != RISCV::NoRegister &&
       Src->getOperand(1).getReg() != Passthru.getReg())