llvm dev - Jul 2007 - [LLVMdev] For the avoidance of doubt...

... can *any* instruction(s) other than load and store cause memory 
reads or writes?

This is pretty important, because I need to be able to track (at least) 
writes, and ideally also reads in order to be able to make 
explicit-state model checking work efficiently.

(I don't really care about reads or writes to spilled registers added by 
the code generator).


Sarah

Sarah Thompson wrote:
> ... can *any* instruction(s) other than load and store cause memory 
> reads or writes?
Not that I know of, but some intrinsic functions do.
> 
> This is pretty important, because I need to be able to track (at least) 
> writes, and ideally also reads in order to be able to make 
> explicit-state model checking work efficiently.
I specifically know that the atomic intrinsic functions I am adding will
write to memory by definition. There may be others that I am not fully
aware of. The LangRef.html has been updated with fairly detailed
information about these intrinsics, but please let me know if there are
unanswered questions.

-Chandler Carruth
> 
> (I don't really care about reads or writes to spilled registers added
by
> the code generator).
> 
> 
> Sarah
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On Mon, 30 Jul 2007, Sarah Thompson wrote:
> ... can *any* instruction(s) other than load and store cause memory
> reads or writes?
Functions calls can (transitively), intrinsics can, and the vaarg 
instruction can (it updates the pointed to list to point to the next 
argument).

-Chris

-- 
http://nondot.org/sabre/
http://llvm.org/

Chris Lattner wrote:
> On Mon, 30 Jul 2007, Sarah Thompson wrote:
>   
>> ... can *any* instruction(s) other than load and store cause memory
>> reads or writes?
>>     
>
> Functions calls can (transitively), 
This isn't a problem because I'll be picking up those reads and writes 
as the function executes anyway.
> intrinsics can, 
Would it be feasible to lower all intrinsics (other than, say, debugging 
intrinsics) as an opt pass, in a similar way to the intrinsic lowering 
that was in the non-JITted interpreter? I don't really care too much 
about the performance hit that this would cause because of the added 
'correctness' it would give, if you see what I
mean.
> and the vaarg 
> instruction can (it updates the pointed to list to point to the next 
> argument).
>   
Useful to know. Thanks.

Sarah

Hi Chandler,
> I specifically know that the atomic intrinsic functions I am adding will
> write to memory by definition. There may be others that I am not fully
> aware of. The LangRef.html has been updated with fairly detailed
> information about these intrinsics, but please let me know if there are
> unanswered questions.
>   
Are these new intrinsics subclasses of MemIntrinsic like the existing 
memmove/memcpy/etc. intrinsics?

[s]