[Bug target/98348] [10 Regression] GCC 10.2 AVX512 Mask regression from GCC 9

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98348

--- Comment #21 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Dávid Bolvanský from comment #20)
> Some small regression (missed opportunity to use vptestnmd):
> 
> Current trunk
> 
> compare(unsigned int __vector(16)):
>   vpxor xmm1, xmm1, xmm1
>   vpcmpd k0, zmm0, zmm1, 0
>   vpmovm2d zmm0, k0
>   ret
> 
> GCC 9.2
> 
> compare(unsigned int __vector(16)):
>   vptestnmd k0, zmm0, zmm0
>   vpmovm2d zmm0, k0
>   ret
> 
> 
> https://gcc.godbolt.org/z/5vK68jM3r

I'm testing 

+(define_insn_and_split "*<avx512>_eq<mode>3"
+  [(set (match_operand:<avx512fmaskmode> 0 "register_operand")
+       (unspec:<avx512fmaskmode>
+         [(match_operand:VI_AVX512BW 1 "nonimm_or_0_operand")
+          (match_operand:VI_AVX512BW 2 "nonimm_or_0_operand")
+          (const_int 0)]
+         UNSPEC_PCMP_ITER))]
+  "TARGET_AVX512F && ix86_pre_reload_split ()
+  && (operands[1] == CONST0_RTX (<MODE>mode)
+      || operands[2] == CONST0_RTX (<MODE>mode))"
+  "#"
+  "&& 1"
+  [(set (match_dup 0)
+       (unspec:<avx512fmaskmode>
+         [(match_dup 1) (match_dup 2)]
+         UNSPEC_MASKED_EQ))])
+