// duplicate only one, because one branch instruction can be eliminated to
// compensate for the duplication.
unsigned MaxDuplicateCount;
- if (MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize))
+ if (TailDuplicateSize.getNumOccurrences() == 0 &&
+ MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize))
MaxDuplicateCount = 1;
else
MaxDuplicateCount = TailDuplicateSize;
if (PreRegAlloc) {
- // Pre-regalloc tail duplication hurts compile time and doesn't help
- // much except for indirect branches.
- if (TailBB->empty() || !TailBB->back().getDesc().isIndirectBranch())
+ if (TailBB->empty())
+ return false;
+ const TargetInstrDesc &TID = TailBB->back().getDesc();
+ // Pre-regalloc tail duplication hurts compile time and doesn't help
+ // much except for indirect branches and returns.
+ if (!TID.isIndirectBranch() && !TID.isReturn())
return false;
// If the target has hardware branch prediction that can handle indirect
// branches, duplicating them can often make them predictable when there
if (!I->isPHI() && !I->isDebugValue())
InstrCount += 1;
}
- // Heuristically, don't tail-duplicate calls if it would expand code size,
- // as it's less likely to be worth the extra cost.
- if (InstrCount > 1 && HasCall)
+ // Don't tail-duplicate calls before register allocation. Calls presents a
+ // barrier to register allocation so duplicating them may end up increasing
+ // spills.
+ if (InstrCount > 1 && (PreRegAlloc && HasCall))
return false;
DEBUG(dbgs() << "\n*** Tail-duplicating BB#" << TailBB->getNumber() << '\n');