[cfe-dev] adding FileSkipped() to PPCallbacks
clattner at apple.com
Fri Apr 16 16:41:20 PDT 2010
On Apr 16, 2010, at 2:38 PM, Zhanyong Wan (λx.x x) wrote:
> On Fri, Apr 16, 2010 at 2:14 PM, Chris Lattner <clattner at apple.com> wrote:
>> On Apr 16, 2010, at 2:09 PM, Zhanyong Wan (λx.x x) wrote:
>>> Thanks for the review, Chris. Please see the new patch. I kept the
>>> signature of FileSkipped() unchanged to be consistent with
>> Keeping the interfaces consistent is nice, but is it really worth it? This will punish other PPCallbacks that don't care about this, like -MM mode and friends. SourceMgr.createFileID isn't hyper-expensive, but it is good to avoid work that no other client at all needs. Sinking this work into the implementation that cares makes sense to me.
> If createFileID() is called here, the file being skipped has already
> been processed earlier, which is a much more expensive operation. So
> do we really want to sacrifice the cleanness of the API for it?
I'm pushing back because the preprocessor is a particularly performance sensitive part of the compiler, and this adds no value for any current clients. I think the cost should be sunk into your client, even if it makes its implementation a little less elegant.
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