This preview shows page 1. Sign up to view the full content.
Unformatted text preview: rectness
• exception behavior &
• data flow
S. Ziavras Exception Behavior
Preserving the exception behavior means that any
the exception behavior
changes in ordering of instr. execution must not
change how exceptions are raised in program
– Often this is relaxed to mean: “the reordering of
this is relaxed to mean: the reordering of
instr. execution must not cause any new
exceptions in program”
If we move the load instr. before the branch, the load may
cause a memory protection exception (HW technique
to be introduced later: speculation
to be introduced later: speculation that ignores exception
when branch is taken)
S. Ziavras Data Flow
Preserving the data flow
Data flow: actual flow of data values among instrs.
that produce results those that consume them
that produce results & those that consume them
Branches make the data flow dynamic, since they
allow the source of data for a given instr. to come
from many points
– Not sufficient to just main...
View Full Document
This document was uploaded on 02/09/2014.
- Fall '09