[Bug rtl-optimization/90209] New: codegen regression (x < 0 ? -x : x) results in branch instead of single instruction on x86_64

[vegard.nossum at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90209

            Bug ID: 90209
           Summary: codegen regression (x < 0 ? -x : x) results in branch
                    instead of single instruction on x86_64
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vegard.nossum at oracle dot com
  Target Milestone: ---

This test case:

double abs1(double x) {
    return x < 0 ? -x : x;
}

used to generate just a single "andpd" instruction before r131381
(5921cbdff68):

abs1:
        andpd   .LC2(%rip), %xmm0
        ret

afterward this revision, it generated this:

fabs1:
        movapd  %xmm0, %xmm1
        ucomisd .LC0(%rip), %xmm0
        jb      .L7
.L2:
        movapd  %xmm1, %xmm0
        ret
.L7:
        jp      .L2
        movsd   .LC1(%rip), %xmm0
        xorpd   %xmm0, %xmm1
        movapd  %xmm1, %xmm0
        ret

The branch is still present on trunk, as can be seen here:

https://godbolt.org/z/P4tQMB

Thanks to jakub for narrowing it down to r131375..r131425.

Three related bugs (AFAICT) are #29253, #62055, and #64897.