[Bug rtl-optimization/53533] [10/11/12/13 regression] vectorization causes loop unrolling test slowdown as measured by Adobe's C++Benchmark

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53533

--- Comment #50 from Hongtao.liu <crazylht at gmail dot com> ---
> 
> On the RTL level likely simplify-rtx (or the variants used by combine)
> only have limited support for vector operations.

Instruction sequence window(more than 20 shift instructions) is too big for
combine, hard to fix it in rtl.