[Bug target/77403] New: [7 Regression] assemble failure of vinserti64x4 with -masm=intel

["zsojka at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77403

            Bug ID: 77403
           Summary: [7 Regression] assemble failure of vinserti64x4 with
                    -masm=intel
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: assemble-failure
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu
             Build: x86_64-pc-linux-gnu

Created attachment 39511
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39511&action=edit
reduced testcase

Output:
$ x86_64-pc-linux-gnu-gcc -O -mavx512f -masm=intel testcase.c
/tmp/cc6ywLFg.s: Assembler messages:
/tmp/cc6ywLFg.s:44: Error: operand size mismatch for `vinserti64x4'

$ grep vinserti64x4 testcase.s 
        vinserti64x4    zmm0, zmm3, ymm0, $0x0

The correct form would be:
        vinserti64x4    zmm0, zmm3, ymm0, 0x0

gcc-6 produces correct assembly.