[cfe-commits] r62475 - in /cfe/trunk: Driver/PrintParserCallbacks.cpp include/clang/Parse/Action.h lib/Parse/ParseExpr.cpp lib/Parse/ParseStmt.cpp lib/Sema/Sema.h lib/Sema/SemaChecking.cpp lib/Sema/SemaExpr.cpp lib/Sema/SemaOverload.cpp

[Douglas Gregor]

On Jan 21, 2009, at 11:52 AM, Daniel Dunbar wrote:

> My performance tester is pointing at this for a 2.5% regression in
> syntax only time.  Is this inherent and the price we have to pay for
> cleanup, or unexpected?
>
> It would be nice if someone could inspect the code generation for the
> smart pointers to see if there is any performance we can reclaim.

Now that the low-level optimizations for DISABLE_SMART_POINTERS in  
r63061are in, I went back to revisit r62475 to see if it's hurting us.

When smart pointers are *enabled*, parsing Cocoa.h (with PTH, -disable- 
free, and -fsyntax-only) is 3% slower due to r62475. So smart pointers  
have some cost when they're enabled (as we'd expect).

When smart pointers are *disabled*, parsing Cocoa.h (with PTH, - 
disable-free, and -fsyntax-only) is .2% slower due to r62475. That's  
in the noise on my system, so smart pointers have a negligible cost  
when they're disabled (as we'd hoped).

I've attached a patch that can be used to roll back r62475 for this  
kind of performance testing (if anyone else wants to try to duplicate  
my results), but I have no intent on ever applying it.  
DISABLE_SMART_POINTERS seems to do the job for our purposes.

We've inspected the code generated by smart pointers and raw pointers  
with the smart pointer functionality disabled (i.e.,  
DISABLE_SMART_POINTERS is defined) in a micro-benchmark of pointer- 
passing through the Action interface, and GCC is producing relatively  
good code. In the micro-benchmark, use of the smart pointer classes  
when the smart-pointer functionality is disabled only results in a 2%  
slowdown.

The micro-benchmark itself is attached; apply it to Clang and run  
Clang on a file containing a single integer to get some simple  
measurements, e.g.,

Smart pointer time = 0.021950s
Raw pointer+ExprResult time = 0.025072s
Raw pointer time = 0.021499s

	- Doug


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> - Daniel
>
> On Sun, Jan 18, 2009 at 4:08 PM, Sebastian Redl
> <sebastian.redl at getdesigned.at> wrote:
>> Author: cornedbee
>> Date: Sun Jan 18 18:08:26 2009
>> New Revision: 62475
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=62475&view=rev
>> Log:
>> Convert more expression actions to smart pointers.
>> Fix type of logical negation for C++.
>>
>> Modified:
>>   cfe/trunk/Driver/PrintParserCallbacks.cpp
>>   cfe/trunk/include/clang/Parse/Action.h
>>   cfe/trunk/lib/Parse/ParseExpr.cpp
>>   cfe/trunk/lib/Parse/ParseStmt.cpp
>>   cfe/trunk/lib/Sema/Sema.h
>>   cfe/trunk/lib/Sema/SemaChecking.cpp
>>   cfe/trunk/lib/Sema/SemaExpr.cpp
>>   cfe/trunk/lib/Sema/SemaOverload.cpp