[Bug tree-optimization/71347] New: [7 regression] Performance drop after r235513 on x86-64 in 32-bit mode.

["ysrumyan at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71347

            Bug ID: 71347
           Summary: [7 regression] Performance drop after r235513 on
                    x86-64 in 32-bit mode.
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ysrumyan at gmail dot com
  Target Milestone: ---

We noticed significant regression (more then 10%) after this revision whicn can
be illustrated on the following simple test-case )attached) - one additional
instruction in innermost loop (scalar replacement is not recognized):

  before r235513                         r235513
.L6:
        movsd   X.1861+8, %xmm2        movsd   -8(%eax), %xmm2
        addl    $8, %eax               movsd   X.1861+8, %xmm1
.L3:
        mulsd   %xmm2, %xmm0           mulsd   %xmm1, %xmm2
        cmpl    $X.1861+64, %eax       addl    $8, %eax
        movsd   %xmm0, (%eax)          movsd   %xmm2, -8(%eax)
        jne     .L6                    cmpl    $X.1861+72, %eax
                                       jne     .L6