diff --git a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp index 38331b614bceb..51c56ecea2c96 100644 --- a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp +++ b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp @@ -712,10 +712,15 @@ bool SIFoldOperandsImpl::updateOperand(FoldCandidate &Fold) const { TII->getRegClass(MI->getDesc(), Fold.UseOpNo, TRI)) { const TargetRegisterClass *NewRC = TRI->getRegClassForReg(*MRI, New->getReg()); - const TargetRegisterClass *ConstrainRC = - TRI->findCommonRegClass(OpRC, Old.getSubReg(), NewRC, New->getSubReg()); - if (!ConstrainRC) - return false; + + const TargetRegisterClass *ConstrainRC = OpRC; + if (New->getSubReg()) { + ConstrainRC = + TRI->getMatchingSuperRegClass(NewRC, OpRC, New->getSubReg()); + + if (!ConstrainRC) + return false; + } if (!MRI->constrainRegClass(New->getReg(), ConstrainRC)) { LLVM_DEBUG(dbgs() << "Cannot constrain " << printReg(New->getReg(), TRI)