[Bug target/93673] New: Fake error given by gcc when compiling for _kshift intrinsics

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93673

            Bug ID: 93673
           Summary: Fake error given by gcc when compiling for _kshift
                    intrinsics
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: crazylht at gmail dot com
  Target Milestone: ---
            Target: i386, x86-64

cat test.c
----
#include<immintrin.h>
#include<assert.h>
__mmask16 i__kshiftli_mask16_KSHIFTLW(__mmask16 arg_0, unsigned int arg_1){
        __mmask16 result;
        switch (arg_1) {
                case 0xFF: // arg_1
                        result = _kshiftli_mask16(arg_0, 0xff);
                        break;
                default: // arg_1
                        assert(false);
                        break;
        }

        return result;
}
---

gcc10_trunk test.c -S -O0 -mavx512f
error:
#1 with x86-64 gcc (trunk)
In file included from
/opt/compiler-explorer/gcc-trunk-20200211/lib/gcc/x86_64-linux-gnu/10.0.1/include/immintrin.h:55,

                 from <source>:1:

<source>: In function '__mmask16 i__kshiftli_mask16_KSHIFTLW(__mmask16,
unsigned int)':

<source>:7:13: error: the last argument must be an 8-bit immediate

    7 |    result = _kshiftli_mask16(arg_0, 0xff);

      |             ^~~~~~~~~~~~~~~~

Compiler returned: 1

But oxFF is already an 8-bit immediate.

Refer to https://godbolt.org/z/xirwxN