diff --git a/llvm/lib/CodeGen/IfConversion.cpp b/llvm/lib/CodeGen/IfConversion.cpp index 5b133a627c4f..64f2faf09de0 100644 --- a/llvm/lib/CodeGen/IfConversion.cpp +++ b/llvm/lib/CodeGen/IfConversion.cpp @@ -615,29 +615,41 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) { BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; bool FalseBBDead = false; bool IterIfcvt = true; - if (!HasEarlyExit && FalseBBI.BB->pred_size() == 2) { - MergeBlocks(TrueBBI, FalseBBI); - FalseBBDead = true; - } else if (!isNextBlock(TrueBBI.BB, FalseBBI.BB)) { - InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII); - TrueBBI.hasFallThrough = false; - if (BBI.ModifyPredicate || TrueBBI.ModifyPredicate) - // Now ifcvt'd block will look like this: - // BB: - // ... - // t, f = cmp - // if t op - // b BBf - // - // We cannot further ifcvt this block because the unconditional branch will - // have to be predicated on the new condition, that will not be available - // if cmp executes. + bool isFallThrough = isNextBlock(TrueBBI.BB, FalseBBI.BB); + if (!isFallThrough) { + // Only merge them if the true block does not fallthrough to the false + // block. By not merging them, we make it possible to iteratively + // ifcvt the blocks. + if (!HasEarlyExit && FalseBBI.BB->pred_size() == 2) { + MergeBlocks(TrueBBI, FalseBBI); + FalseBBDead = true; + // Mixed predicated and unpredicated code. This cannot be iteratively + // predicated. IterIfcvt = false; + } else { + InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII); + TrueBBI.hasFallThrough = false; + if (BBI.ModifyPredicate || TrueBBI.ModifyPredicate) + // Now ifcvt'd block will look like this: + // BB: + // ... + // t, f = cmp + // if t op + // b BBf + // + // We cannot further ifcvt this block because the unconditional branch will + // have to be predicated on the new condition, that will not be available + // if cmp executes. + IterIfcvt = false; + } } // Now merge the entry of the triangle with the true block. BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); MergeBlocks(BBI, TrueBBI); + // Remove entry to false edge. + if (BBI.BB->isSuccessor(FalseBBI.BB)) + BBI.BB->removeSuccessor(FalseBBI.BB); std::copy(BBI.BrCond.begin(), BBI.BrCond.end(), std::back_inserter(BBI.Predicate));