1 files changed, 9 insertions, 0 deletions
diff --git a/llvm/lib/Target/RISCV/RISCVVectorPeephole.cpp b/llvm/lib/Target/RISCV/RISCVVectorPeephole.cpp
index 84ef53985484..c1cc19b503de 100644
--- a/llvm/lib/Target/RISCV/RISCVVectorPeephole.cpp
+++ b/llvm/lib/Target/RISCV/RISCVVectorPeephole.cpp
@@ -434,6 +434,15 @@ bool RISCVVectorPeephole::convertSameMaskVMergeToVMv(MachineInstr &MI) {
   if (!isKnownSameDefs(TrueMask.getReg(), MIMask.getReg()))
     return false;
 
+  // Masked off lanes past TrueVL will come from False, and converting to vmv
+  // will lose these lanes unless MIVL <= TrueVL.
+  // TODO: We could relax this for False == Passthru and True policy == TU
+  const MachineOperand &MIVL = MI.getOperand(RISCVII::getVLOpNum(MI.getDesc()));
+  const MachineOperand &TrueVL =
+      True->getOperand(RISCVII::getVLOpNum(True->getDesc()));
+  if (!RISCV::isVLKnownLE(MIVL, TrueVL))
+    return false;
+
   // True's passthru needs to be equivalent to False
   Register TruePassthruReg = True->getOperand(1).getReg();
   Register FalseReg = MI.getOperand(2).getReg();