https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109088
--- Comment #7 from JuzheZhong <juzhe.zhong at rivai dot ai> --- Update the analysis: We failed to recognize it as reduction because, the PHI result has 2 uses: # result_20 = PHI <result_9(8), 0(18)> ... _11 = result_20 + 10; --------> first use result_17 = _4 + _11; _23 = _4 > _7; result_9 = _23 ? result_17 : result_20; -----> second use It seems that it is the if-conversion issue which makes loop vectorizer failed to vectorize it. I have checked LLVM implementation, their "result" ssa always has single use no matter how I modify the codes (for example, result += a[i] + b[i] + c[i]).
