[Bug target/84786] New: [miscompilation] vunpcklpd accessing xmm16-22 targeting KNL

[kretz at kde dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84786

            Bug ID: 84786
           Summary: [miscompilation] vunpcklpd accessing xmm16-22
                    targeting KNL
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kretz at kde dot org
  Target Milestone: ---

I see generated code, such as:

  424821:·   vpxord %zmm17,%zmm17,%zmm17
  424827:·   vpxord %zmm18,%zmm18,%zmm18
[...]
  424855:·   vunpcklpd %xmm17,%xmm0,%xmm1
[...]
  424891:·   vunpcklpd %xmm18,%xmm1,%xmm1

when compiling with `-O2 -march=knl`. Apparently the `_mm_unpacklo_pd`
intrinsic is incorrectly translated to an encoding that allows the upper 16
SIMD registers for the first register.

Reducing a test case will take some time.