... continuing with a different compiler (SDCC)

Here are the programs:

1.  c=c/2&85|c*2&170;c=c/4&51|c*4&204;RT c>>4|c<<4;       // (47 bytes)
2.  UC r,i=8;WH(i--){r>>=1;r|=c&128;c*=2;}RT r;           // (43 bytes)
3.  UC r,i=8;WH(i--){r*=2;r|=c&1;c/=2;}RT r;              // (40 bytes)
4.  UC r,i=8;WH(i--){r=r*2|c&1;c/=2;}RT r;                // (38 bytes)
5.  UC r,i=8;WH(i--)r=r*2|c&1,c/=2;RT r;                  // (36 bytes)
6.  UC r,i=1;WH(r+=c&i?r++:r,i+=i);RT r;                  // (36 bytes)
7.  IN r=1;WH(r<256)r=r*2|c&1,c/=2;RT r;                  // (36 bytes)
8.  UC r,i=1;WH(r+=r+c/i%2,i+=i);RT r;                    // (34 bytes)

And here is a summary of the results

Program   Length of generated code

   1               38
   2               27
   3               27
   4               27
   5               27
   6               27
   7               43
   8               22

Here's the generated code for #8:

   00E7                     306 _TestFlip:
   00E7 AA 82               307         mov     r2,dpl
                            308 ;       testflip.c:138: UC r,i=1;WH(r+=r+c/i%2,i+=i);RT r;
   00E9 7B 01               309         mov     r3,#0x01
   00EB                     310 00101$:
   00EB 8B F0               311         mov     b,r3
   00ED EA                  312         mov     a,r2
   00EE 84                  313         div     ab
   00EF 54 01               314         anl     a,#0x01
   00F1 2D                  315         add     a,r5
   00F2 2D                  316         add     a,r5
   00F3 FD                  317         mov     r5,a
   00F4 EB                  318         mov     a,r3
   00F5 2B                  319         add     a,r3
   00F6 FC                  320         mov     r4,a
   00F7 FB                  321         mov     r3,a
   00F8 70 F1               322         jnz     00101$
   00FA 8D 82               323         mov     dpl,r5
   00FC 22                  324         ret

As for assembly versions of the code I think one need not look further than this one by Peter Dannegger:)
http://home.tiscali.de/peterd/ap.../index.htm