According to the latests documentation from Intel, the kmovw instruction
zeros the higher part of a GP register:

    KMOVW
    IF *destination is a memory location*
        DEST[15:0] <- SRC[15:0]
    IF *destination is a mask register or a GPR *
        DEST <- ZeroExtension(SRC[15:0])

GCC adds superfluous movzwl after kmovw:

Program:

    #include <stdint.h>
    #include <immintrin.h>

    uint32_t test(__m512i a, __m512i b) {
        
        uint32_t c = _mm512_cmpeq_epi32_mask(a, b);
        return c;
    }

Invocation:

$ gcc-5 --version
gcc-5 (Debian 5.3.1-13) 5.3.1 20160323
$ gcc-5 -O3 -S -mavx512f report.cpp

Assembly output:

	vpcmpeqd	%zmm1, %zmm0, %k1
	kmovw	%k1, %eax
	movzwl	%ax, %eax <<<< HERE
	ret