llvm-project

5e54c923 - [VPlan] Fix crash when unrolling in-loop reduction chains (#129840)

[VPlan] Fix crash when unrolling in-loop reduction chains (#129840) If an in-loop reduction is chained e.g. WIDEN-REDUCTION-PHI ir<%rdx> = phi ir<0>, ir<%add2> REDUCE ir<%add1> = ir<%rdx> + reduce.add (ir<%x>) REDUCE ir<%add2> = ir<%add1> + reduce.add (ir<%y>) When we try to unroll the second add reduction, we crash because we currently expect the chain to be a VPReductionPHIRecipe, when in fact it's the previous reduction. This relaxes the cast to a dyn_cast, so we end up unrolling to: WIDEN-REDUCTION-PHI ir<%rdx> = phi ir<0>, ir<%add2> WIDEN-REDUCTION-PHI ir<%rdx>.1 = phi ir<0>, ir<%add2>.1, ir<1> WIDEN-REDUCTION-PHI ir<%rdx>.2 = phi ir<0>, ir<%add2>.2, ir<2> WIDEN-REDUCTION-PHI ir<%rdx>.3 = phi ir<0>, ir<%add2>.3, ir<3> REDUCE ir<%add1> = ir<%rdx> + reduce.add (ir<%x>) REDUCE ir<%add1>.1 = ir<%rdx>.1 + reduce.add (ir<%x>.1) REDUCE ir<%add1>.2 = ir<%rdx>.2 + reduce.add (ir<%x>.2) REDUCE ir<%add1>.3 = ir<%rdx>.3 + reduce.add (ir<%x>.3) REDUCE ir<%add2> = ir<%add1> + reduce.add (ir<%y>) REDUCE ir<%add2>.1 = ir<%add1>.1 + reduce.add (ir<%y>.1) REDUCE ir<%add2>.2 = ir<%add1>.2 + reduce.add (ir<%y>.2) REDUCE ir<%add2>.3 = ir<%add1>.3 + reduce.add (ir<%y>.3) This fixes a crash when building 525.x264_r from SPEC CPU 2017 on AArch64 with -mllvm -prefer-inloop-reductions