I happened to be single stepping through this function and noticed the cursor skipping over this particular test.  gcc had optimized it out even though I had compiled gdb with -O0.  Looking at the test it's easy to see why: it can never succeed.

      else if ((op & 0xfc1f016a) == 0x7c01016e) // <<<< can never succeed
        {       		/* stwux rX,r1,rY */
          /* No way to figure out what r1 is going to be.  */
          fdata->frameless = 0;
          offset = fdata->offset;
          continue;
        }