[Bug tree-optimization/100173] telecom/viterb00data_1 has 16.92% regression compared O2 -ftree-vectorize -fvect-cost-model=very-cheap to O2 on CLX/ICX, 9% regression on znver3

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100173

--- Comment #4 from Hongtao.liu <crazylht at gmail dot com> ---

> but yes, cselim will also sink the first store, moving it across the

Can we also sink loads? assign pointer to another temp pointer in both if and
else bb, and then load val from this temp pointer. those assignments that in if
and else branch would be finially transformed to conditional mov. 

performance can benifit 100% with below change.

 for (i = 0; i < (1<<5)/2; i++) {

    esMetricIn = *pBranchMetric++;

    esMetric1 = pIn1->m_esPathMetric - esMetricIn;
    esMetric2 = pIn2->m_esPathMetric + esMetricIn;

    e_s16 *t1p = (esMetric1 >= esMetric2) ? &(pIn1->m_esState) :
&(pIn2->m_esState);
    e_s16 t1  = (esMetric1 >= esMetric2) ? esMetric1 : esMetric2;
    pOut->m_esPathMetric = t1;
    pOut->m_esState = *t1p << 1;
    pOut++;

    esMetric1 = pIn1->m_esPathMetric + esMetricIn;
    esMetric2 = pIn2->m_esPathMetric - esMetricIn;

    e_s16 *t2p = (esMetric1 >= esMetric2) ? &(pIn1->m_esState) :
&(pIn2->m_esState);
    e_s16 t2  = (esMetric1 >= esMetric2) ? esMetric1 : esMetric2;
    pOut->m_esPathMetric = t2;
    pOut->m_esState = *t2p << 1;
    pOut++;

    pIn1++;
    pIn2++;
  }