LFSR in 386 assembly

Don't hold it against me. This is with the x^32+x^31+x^29+x+1 poly from the wikipedia page on linear feedback shift registers.

do {
  lfsr = (lfsr >> 1) ^ (unsigned int)(0 - (lfsr & 1u) & 0xd0000001u); 
} while(lfsr != 1u);

cute trick, but compiles to this:

        movl    $1, %ebx
L2:
        movl    %ebx, %edx
        andl    $1, %ebx
        negl    %ebx
        shrl    %edx
        andl    $-805306367, %ebx
        xorl    %edx, %ebx
        cmpl    $1, %ebx
        jne     L2

The carry flag will be set from the shift, so we can use sub with borrow to set eax to 0 or -1. With my not-very-accurate measurements, 7 seconds (down from 9) to go through 2^32:

        mov     edx, 1
L2:
        shr     edx
        sbb     eax, eax
        and     eax, 0xd0000001
        xor     edx, eax
        cmp     edx, 1
        jne     L2

Thanks Phil for the idea!