Performance regression

[Dale Johannesen]

On Wednesday, September 25, 2002, at 08:44 AM, Roger Sayle wrote:
> On 25 Sep 2002, Jim Wilson wrote:
>> This has been discussed many times before.  The only way to avoid 
>> performance
>> loss from changing the semantics of LOAD_EXTEND_OP is to add new 
>> optimizer
>> support for sign/zero extend operations.
>>
>> Since we went ahead with the LOAD_EXTEND_OP change to fix optimizer 
>> bugs,
>> it would be useful if someone was looking into the new optimization 
>> support
>> we need.  Maybe it can go on the projects list?  Add support for 
>> optimizing
>> sign/zero extend operations.  Some problems can be fixed by being 
>> careful
>> in the md file, but some problems can be solved only with an 
>> optimization
>> pass that is designed to optimize away redundant sign/zero extend 
>> operations.
>
> I'm more than happy to work on adding some sign/zero extend 
> optimizations
> to the GCC's RTL optimizers.  I just didn't want to clash with Dale, if
> Apple wanted to start work on it straight away.

At the moment this isn't showing up as a big performance hit, so I 
doubt we'll
be working on it soon.  As always that could change.