fixup! respond to review

Author: michaelmaitland

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -4243,21 +4243,6 @@ bool RISCV::isVLKnownLE(const MachineOperand &LHS, const MachineOperand &RHS) {
   return LHS.getImm() <= RHS.getImm();
 }
 
-/// Given two VL operands, do we know that LHS < RHS?
-bool RISCV::isVLKnownLT(const MachineOperand &LHS, const MachineOperand &RHS) {
-  if (LHS.isReg() && RHS.isReg() && LHS.getReg().isVirtual() &&
-      LHS.getReg() == RHS.getReg())
-    return false;
-  if (RHS.isImm() && RHS.getImm() == RISCV::VLMaxSentinel && LHS.isImm() &&
-      LHS.getImm() != RHS.getImm())
-    return true;
-  if (LHS.isImm() && LHS.getImm() == RISCV::VLMaxSentinel)
-    return false;
-  if (!LHS.isImm() || !RHS.isImm())
-    return false;
-  return LHS.getImm() < RHS.getImm();
-}
-
 namespace {
 class RISCVPipelinerLoopInfo : public TargetInstrInfo::PipelinerLoopInfo {
   const MachineInstr *LHS;

llvm/lib/Target/RISCV/RISCVInstrInfo.h

@@ -356,9 +356,6 @@ static constexpr int64_t VLMaxSentinel = -1LL;
 /// Given two VL operands, do we know that LHS <= RHS?
 bool isVLKnownLE(const MachineOperand &LHS, const MachineOperand &RHS);
 
-/// Given two VL operands, do we know that LHS < RHS?
-bool isVLKnownLT(const MachineOperand &LHS, const MachineOperand &RHS);
-
 // Mask assignments for floating-point
 static constexpr unsigned FPMASK_Negative_Infinity = 0x001;
 static constexpr unsigned FPMASK_Negative_Normal = 0x002;

llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp

@@ -1311,8 +1311,15 @@ bool RISCVVLOptimizer::tryReduceVL(MachineInstr &MI) {
     unsigned VLOpNum = RISCVII::getVLOpNum(MI.getDesc());
     MachineOperand &VLOp = MI.getOperand(VLOpNum);
 
-    if (!RISCV::isVLKnownLT(*CommonVL, VLOp)) {
-      LLVM_DEBUG(dbgs() << "    Abort due to CommonVL not < VLOp.\n");
+    if (!RISCV::isVLKnownLE(*CommonVL, VLOp)) {
+      LLVM_DEBUG(dbgs() << "    Abort due to CommonVL not <= VLOp.\n");
+      continue;
+    }
+
+    if (CommonVL->isIdenticalTo(VLOp)) {
+      LLVM_DEBUG(
+          dbgs()
+          << "    Abort due to CommonVL == VLOp, no point in reducing.\n");
       continue;
     }