fmt.Fprintf(os.Stderr, "=-= writing counter segment header: %+v", cfw.csh)
	}
	if err := binary.Write(ws, binary.LittleEndian, cfw.csh); err != nil {
		return err
	}
	// ... and finally return to the original offset.
	if _, err := ws.Seek(off, io.SeekStart); err != nil {
		return fmt.Errorf("error seeking in patchSegmentHeader: %v", err)
	}
	return nil
}

TEXT asmtest(SB),DUPOK|NOSPLIT,$0
lable1:
	BFPT	1(PC)			// 00050048
	BFPT	lable1	// BFPT 2	//1ffdff4b

lable2:
	BFPF	1(PC)			// 00040048
	BFPF	lable2	// BFPF 4 	// 1ffcff4b

	// relocation in play so the assembled offset should be 0
	JMP	foo(SB)			// 00000050

	JMP	(R4)			// 8000004c
	JMP	1(PC)			// 00040050
	MOVW	$65536, R4		// 04020014
	MOVW	$4096, R4		// 24000014
	MOVV	$65536, R4		// 04020014
	MOVV	$4096, R4		// 24000014

	}

	for i := range classes {
		computeDivMagic(&classes[i])
	}

	return classes
}

// computeDivMagic checks that the division required to compute object
// index from span offset can be computed using 32-bit multiplication.
// n / c.size is implemented as (n * (^uint32(0)/uint32(c.size) + 1)) >> 32
// for all 0 <= n <= c.npages * pageSize
func computeDivMagic(c *class) {
	// divisor
	d := c.size