[whopr] Design/implementation alternatives for the driver and WPA

Chris Lattner clattner@apple.com
Thu Jun 5 21:47:00 GMT 2008


On Jun 5, 2008, at 2:03 PM, Ian Lance Taylor wrote:

> Nick Kledzik <kledzik@apple.com> writes:
>
>>> How does the linker tell LTO that a symbol may be inlined, but must
>>> also be externally visible?
>> The linker just tells LTO which symbols must remain.  The LTO engine
>> is free to inline anything that would improve codegen, with the
>> exception
>> that any weak definition that must remain (preserved) cannot be  
>> inlined.
>
> I'll just note that that isn't optimal for ELF when producing an
> executable.

Why? Because you have to touch (worst case) every symbol?  The cost of  
doing LTO *dramatically* dwarfs the cost of touching symbols  
once.  :)  You're right this could be improved, and we're actively  
working on it... but it seems like a strange thing to worry about vs  
correctness in all cases.

-Chris



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