[LLVMdev] Exception Table Padding Change

Garrison Venn gvenn.cfe.dev at gmail.com
Fri Feb 5 18:27:31 PST 2010


Hi Bill,

Just to verify that I understand correctly, the proposal should not have any affect on pre-existing code since we
already call readULEB128(...) for the call-site table length. High bit set for 3 bytes results in 4 byte read as per
uleb128. This is obvious now that I've taken time to write this, but hey if nothing else it helps the list. :-)

Garrison

PS: Are you still revamping the llvm exception API as you proposed a couple of months ago, or was this effort
ditched? 

On Feb 5, 2010, at 20:44, Bill Wendling wrote:

> On Feb 5, 2010, at 4:00 PM, Duncan Sands wrote:
> 
>> Hi Bill,
>> 
>>> It looks like your goal is to keep the 32-bit pointers in the call-site table 4-byte aligned. Here is another solution, instead of having two labels at the start of the LSDA (with pad bytes between them), have no pad bytes and instead use an unnormalized uleb128 for the call-site table length. By unnormalized, I mean one with leading zeros. For instance, instead of:
>> 
>> this sounds like a good idea to me.
>> 
> Great! Thanks, Duncan. :-)
> 
> -bw
> 
> 
> 
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