• http://booksite.mkp.com/9780123838728/references/appendix_h.pdf (Hardware and Software for VLIW and EPIC)

• Book

  Hennessy, Patterson: Computer Architecture: A Quantitative Approach, 5th Edition

• Page 29:

    There are four methods that have been investigated for supporting more
    ambitious speculation without introducing erroneous exception behavior:

    [...]

    1. The hardware and operating system cooperatively ignore exceptions for
       speculative instructions. As we will see later, this approach preserves
       exception behavior for correct programs, but not for incorrect ones. This
       approach may be viewed as unacceptable for some programs, but it has been
       used, under program control, as a “fast mode” in several processors.

    2. Speculative instructions that never raise exceptions are used, and checks
       are introduced to determine when an exception should occur

    3. A set of status bits, called _poison bits_, are attached to the result
       registers written by speculated instructions when the instructions cause
       exceptions. The _poison bits_ cause a fault when a normal instruction
       attempts to use the register.

    4. A mechanism is provided to indicate that an instruction is speculative,
       and the hardware buffers the instruction result until it is certain that
       the instruction isno longer speculative.

• More details on how it's implemented on Page 31 and Page 32.