[Cisc662010_fa08] An interrupt or exception is imprecise if ...
taufer at cis.udel.edu
Sun Sep 28 16:04:33 EDT 2008
Last time we discussed in class when an interrupt or exception is
precise and we saw this definition:
An interrupt or exception is considered precise if there is a single
instruction (or interrupt point) for which:
- All instructions before that have committed their state
- No following instructions (including the interrupting instruction)
have modified any state.
Alternatively, to define the same concept we can also explain when an
interrupt or exception is NOT precise, e.g.:
An interrupt or exception is imprecise if the processor state when an
exception is raised does not look exactly as if the instructions were
executed sequentially in strict program order:
- The pipeline may have already completed instructions that are later
in program order than the instruction causing the exception (we may
have div.d raising an exception but have sub.d completed already).
- The pipeline may have not yet completed some instructions that are
earlier in program order than the instruction causing the exception.
Department of Computer and Information Sciences
University of Delaware
Phone: (302) 831 0071
Fax: (302) 831 8458
E-Mail: taufer at acm.org
D at H: http://docking.cis.udel.edu
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