llvm dev - Sep 2011 - [LLVMdev] readnone

Nick Lewycky wrote:
> I was sure that I remember "opt -functionattrs" being taught to
do this,
> but I just tried it out and it doesn't. This is a missed optz'n
> opportunity, testcase:
>
>     @x = constant i32 0
>     define void @foo() {
>       load i32* @x
>       ret void
>     }
>
> is only marked readonly when it should be readnone. Could I interest you
> in fixing that? :)
Never mind, it's because the default AA is no-aa, which answers no to 
everything. "opt -basicaa -functionattrs" gets this testcase right
(and
the one that stores, too!)

Nick

Thanks for the answer Nick. Now you got me on a chase through FunctionAttrs.cpp
trying to find out what analysis passes "... which answers no to
everything", means. :-)

Garrison

On Sep 10, 2011, at 13:52, Nick Lewycky wrote:
> Nick Lewycky wrote:
>> I was sure that I remember "opt -functionattrs" being taught
to do this,
>> but I just tried it out and it doesn't. This is a missed optz'n
>> opportunity, testcase:
>> 
>>    @x = constant i32 0
>>    define void @foo() {
>>      load i32* @x
>>      ret void
>>    }
>> 
>> is only marked readonly when it should be readnone. Could I interest
you
>> in fixing that? :)
> 
> Never mind, it's because the default AA is no-aa, which answers no to
everything. "opt -basicaa -functionattrs" gets this testcase right
(and the one that stores, too!)
> 
> Nick

Reading the comments for:

	AliasAnalysis::onlyAccessesArgPointees(...) and
	AliasAnalysis::doesAccessArgPointees(...)

And uses of these signatures in FunctionAttrs.cpp such as:

	if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
          // If the call does access argument pointees, check each argument.
          if (AliasAnalysis::doesAccessArgPointees(MRB))

Wouldn't AliasAnalysis::onlyAccessesArgPointees(...) being renamed something
like:

AliasAnalysis::atMostAccessesArgPointees(...), be clearer?

The "only" prefix throws me off at least.

Sorry if this is noise.

Garrison

On Sep 10, 2011, at 14:26, Garrison Venn wrote:
> Thanks for the answer Nick. Now you got me on a chase through
FunctionAttrs.cpp
> trying to find out what analysis passes "... which answers no to
everything", means. :-)
> 
> Garrison
> 
> On Sep 10, 2011, at 13:52, Nick Lewycky wrote:
> 
>> Nick Lewycky wrote:
>>> I was sure that I remember "opt -functionattrs" being
taught to do this,
>>> but I just tried it out and it doesn't. This is a missed
optz'n
>>> opportunity, testcase:
>>> 
>>>   @x = constant i32 0
>>>   define void @foo() {
>>>     load i32* @x
>>>     ret void
>>>   }
>>> 
>>> is only marked readonly when it should be readnone. Could I
interest you
>>> in fixing that? :)
>> 
>> Never mind, it's because the default AA is no-aa, which answers no
to everything. "opt -basicaa -functionattrs" gets this testcase right
(and the one that stores, too!)
>> 
>> Nick
> 
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