static std::vector<InstructionTemplate> generateSnippetUsingStaticRenaming(
const LLVMState &State, const InstructionTemplate &IT,
const ArrayRef<const Variable *> TiedVariables,
const BitVector *ScratchSpaceAliasedRegs) {
std::vector<InstructionTemplate> Instructions;
// Assign registers to variables in a round-robin manner. This is simple but
// ensures that the most register-constrained variable does not get starved.
std::vector<BitVector> PossibleRegsForVar;
for (const Variable *Var : TiedVariables) {
assert(Var);
const Operand &Op = IT.Instr.getPrimaryOperand(*Var);
assert(Op.isReg());
BitVector PossibleRegs = State.getRATC().emptyRegisters();
if (ScratchSpaceAliasedRegs) {
PossibleRegs |= *ScratchSpaceAliasedRegs;
}
PossibleRegs.flip();
PossibleRegs &= Op.getRegisterAliasing().sourceBits();
PossibleRegsForVar.push_back(std::move(PossibleRegs));
}
SmallVector<int, 2> Iterators(TiedVariables.size(), 0);
while (true) {
InstructionTemplate TmpIT = IT;
// Find a possible register for each variable in turn, marking the
// register as taken.
for (size_t VarId = 0; VarId < TiedVariables.size(); ++VarId) {
const int NextPossibleReg =
PossibleRegsForVar[VarId].find_next(Iterators[VarId]);
if (NextPossibleReg <= 0) {
return Instructions;
}
TmpIT.getValueFor(*TiedVariables[VarId]) =
llvm::MCOperand::createReg(NextPossibleReg);
// Bump iterator.
Iterators[VarId] = NextPossibleReg;
// Prevent other variables from using the register.
for (BitVector &OtherPossibleRegs : PossibleRegsForVar) {
OtherPossibleRegs.reset(NextPossibleReg);
}
}
Instructions.push_back(std::move(TmpIT));
}
}
