[llvm-commits] [llvm] r55638 - /llvm/trunk/include/llvm/Function.h

[Devang Patel]

On Sep 3, 2008, at 4:09 AM, Anton Korobeynikov wrote:

> Hello, Devang
>
>> +typedef unsigned FunctionNotes;
>> +const FunctionNotes FP_None            = 0;
>> +const FunctionNotes FP_NoInline        = 1<<0;
>> +const FunctionNotes FP_AlwaysInline    = 1<<1;
>> +const FunctionNotes FP_OptimizeForSize = 1<<2;
> I don't see, how this differs from attribute applied to result of
> function. Also, how this is connected with your proposal? From your
> proposal I thought, that notes should allow users to pass arbitrary
> strings to differents parts of their code,  allowing them to parse and
> use them accordingly.

No, that was not the goal. These notes are not a replacement for  
annotation instructions.

> Are we planning to add new "type" of note here each time we need it?
> This seems to be pretty inconvenient. What will happen, when we'll
> have > 64 different notes, or, "variadic" notes, say "foo=N", where N
> can be any integer (for example, some threshold, etc)?

The idea is to encode the reason that impacts some threshold instead  
of directly encoding threshold. Because the threshold is usually  
specific to a transformation where the reason behind the threshold may  
impact other passes also, for example encoding optimize-for-size is a  
better then encoding inline-threshold=200.

<offtopic> IMO, thresholds are implementation details that never  
should be exposed to end users. We, llvm developers, should fine tune  
them to meet developers' needs. The magic numbers associated with a  
threshold usually confuses developers and restricts llvm developers.  
For example, keep meaning of -inline-threshold=200 consistent even  
though you fixed a bug in how inline costs are calculated! </offtopic>

> Are we planning
> to drop "custom" notes? If yes - them now I'm just seeing duplicating
> existing paramattrs functionality.

paramattrs are associated with parameter, this is associated with the  
definition. Some of the paramattrs can be used with call/invoke  
instructions, e.g. nounwind. Where as notes are never associated with  
call/invoke instruction.

-
Devang