chapter3-m2-ziavras

Ziavras exception behavior preserving the exception

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Unformatted text preview: rectness correctness • exception behavior & o • data flow S. Ziavras Exception Behavior Preserving the exception behavior means that any the exception behavior that any 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” DADDU BEQZ LW R2,R3,R4 R2,L1 R1,0(R2) L1: 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 ignores exception when branch is taken) S. Ziavras Data Flow Preserving the data flow th fl • 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...
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This document was uploaded on 02/09/2014.

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