On Jul 30, 2013, at 14:31, Ryan Schmidt <[email protected]> wrote:

> 
> On Jul 30, 2013, at 09:49, Landon J Fuller wrote:
> 
>> Without actually measuring the gains, there's no guarantee that these 
>> changes will actually improve performance, and in moving away from the 
>> optimization flags et al selected by the original developers, could very 
>> possibly trigger bugs in code generation output (e.g., compiler bugs, 
>> especially with bleeding-edge clang), or reveal bugs in the project that 
>> aren't apparent at lower optimization levels.
> 
> All ports in MacPorts already move away from the optimization flags selected 
> by the original developers. MacPorts 2.2 sets optflags to -Os, to match what 
> Apple uses to compile the software distributed with OS X; previous versions 
> of MacPorts set optflags to -O2. Most ports don't care what optimization 
> flags are used and respect the values MacPorts provides. Some ports do care 
> and their build systems (or in some cases their portfiles) override what 
> MacPorts sets.

-Os is a much safer default in that its widely tested and a reasonable 
conservative choice. All Xcode projects default to -Os, and as you noted,  
Apple ships most of their code compiled with -Os. The setting is also less 
aggressive than -O2, and unlikely to result in any surprises for the original 
developers.

-landonf
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