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[RISCV][VLOPT] Do not optimize VL when isVectorOpUsedAsScalarOp #120291

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Merged
merged 1 commit into from
Dec 17, 2024
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[RISCV][VLOPT] Do not optimize VL when isVectorOpUsedAsScalarOp #120291

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9 changes: 3 additions & 6 deletions llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -887,13 +887,10 @@ bool RISCVVLOptimizer::checkUsers(const MachineOperand *&CommonVL,
// Instructions like reductions may use a vector register as a scalar
// register. In this case, we should treat it like a scalar register which
// does not impact the decision on whether to optimize VL.
// TODO: Treat it like a scalar register instead of bailing out.
if (isVectorOpUsedAsScalarOp(UserOp)) {
[[maybe_unused]] Register R = UserOp.getReg();
[[maybe_unused]] const TargetRegisterClass *RC = MRI->getRegClass(R);
assert(RISCV::VRRegClass.hasSubClassEq(RC) &&
"Expect LMUL 1 register class for vector as scalar operands!");
LLVM_DEBUG(dbgs() << " Use this operand as a scalar operand\n");
continue;
CanReduceVL = false;
break;
}

if (mayReadPastVL(UserMI)) {
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