[llvm-commits] annotate known function declarations in SimplifyLibCalls pass

[Nick Lewycky]

Duncan Sands wrote:
> Hi Nick,
>
>   
>> +  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
>> +    Function &F = *I;
>> +    const FunctionType *FTy = F.getFunctionType();
>>     
>
> probably you only want to consider function declarations, not those
> with bodies.
>
>   
Done.
>> +        if (NameLen == 6 && !strcmp(NameStr, "strlen")) {
>> +          if (FTy->getNumParams() == 0 ||
>>     
>
> Shouldn't this be "FTy->getNumParams() != 1"?
>
>   
>> +          if (!F.paramHasAttr(1, Attribute::NoCapture)) {
>>     
>
> How about adding a "doesNotCapture" convenience method?
>
>   
Done.
>> +            F.addAttribute(1, Attribute::NoCapture);
>>     
>
> How about adding setDoesNotCapture too.
>
>   
>> +          if (FTy->getNumParams() < 2 ||
>>     
>
> Shouldn't this be != 2?  OK, I guess some take an extra argument.
> But then shouldn't the type of the extra argument be checked?
>
>   
When this pass is run, we're allowed to assume that the functions are 
meant to be the well-known ones. The point of the test is to prevent 
crashes if somebody forgets their #include and we end up with a .ll like:

  declare i32 @strlen(...)

and we'd crash trying to mark the first parameter as nocapture. There's 
no need to test any parameters we aren't modifying, so I happily merge 
cases where functions have different number of parameters so long as 
we're doing the same thing with them.
> Otherwise looks good, except for the lack of a testcase.
>
>   
Right! I'll write one and submit.

Thanks!

Nick