[Bug middle-end/110148] [14 Regression] TSVC s242 regression between g:c0df96b3cda5738afbba3a65bb054183c5cd5530 and g:e4c986fde56a6248f8fbe6cf0704e1da34b055d8

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110148

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Lili Cui <cuilili@gcc.gnu.org>:

https://gcc.gnu.org/g:4633e38cd22c5e51fac984124c7627be912d0999

commit r14-2185-g4633e38cd22c5e51fac984124c7627be912d0999
Author: Lili Cui <lili.cui@intel.com>
Date:   Thu Jun 29 06:51:56 2023 +0000

    Avoid adding loop-carried ops to long chains

    Avoid adding loop-carried ops to long chains, otherwise the whole chain
will
    have dependencies across the loop iteration. Just keep loop-carried ops in
a
    separate chain.
       E.g.
       x_1 = phi(x_0, x_2)
       y_1 = phi(y_0, y_2)

       a + b + c + d + e + x1 + y1

       SSA1 = a + b;
       SSA2 = c + d;
       SSA3 = SSA1 + e;
       SSA4 = SSA3 + SSA2;
       SSA5 = x1 + y1;
       SSA6 = SSA4 + SSA5;

    With the patch applied, these test cases improved by 32%~100%.

    S242:
    for (int i = 1; i < LEN_1D; ++i) {
        a[i] = a[i - 1] + s1 + s2 + b[i] + c[i] + d[i];}

    Case 1:
    for (int i = 1; i < LEN_1D; ++i) {
        a[i] = a[i - 1] + s1 + s2 + b[i] + c[i] + d[i] + e[i];}

    Case 2:
    for (int i = 1; i < LEN_1D; ++i) {
        a[i] = a[i - 1] + b[i - 1] + s1 + s2 + b[i] + c[i] + d[i] + e[i];}

    The value is the execution time
    A: original version
    B: with FMA patch g:e5405f065bace0685cb3b8878d1dfc7a6e7ef409(base on A)
    C: with current patch(base on B)

              A       B       C     B/A             C/A
    s242    2.859   5.152   2.859   1.802028681     1
    case 1  5.489   5.488   3.511   0.999818        0.64
    case 2  7.216   7.499   4.885   1.039218        0.68

    gcc/ChangeLog:

            PR tree-optimization/110148
            * tree-ssa-reassoc.cc (rewrite_expr_tree_parallel): Handle
loop-carried
            ops in this function.