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From: Julian S. <js...@ac...> - 2012-03-02 12:17:34
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On Thursday, February 23, 2012, Florian Krohm wrote: > On 02/23/2012 03:28 AM, Julian Seward wrote: > > So .. apart from the curiosity value, I am not sure what this will buy > > you in the general case. Maybe you are doing some bizarre experiment > > with your handwritten assembly version of _start? > > Yeah...to satisfy your curiosity here's the story. > Long time ago when I did the 128-bit floating point implementation for > s390 I wrote some testing machinery that made sure memcheck propagated > the undefinedness through the new IROps properly. Basically > - load an undefined value into a register > - AND it with a one-hot bit-pattern (leaving a single bit undefined) > - perform the operation we're interested in > - do a conditional branch on the result > - depending on the operation the conditional branch would test > a specific bit or all of them > - check for reported error This all seems an excellent thing to do (I wish we had more of it). However .. wouldn't it be a bit easier by wrapping each insn up in a bit of inline assembly, and feeding it data from some uninitialised block? Then you could do a whole bunch at once rather than creating one executable per insn. Just my Eur 0.02. [Am sure you've already thought of this, btw ..] J |