Re: Xcode 5.1 compiler option -Ofast
Re: Xcode 5.1 compiler option -Ofast
- Subject: Re: Xcode 5.1 compiler option -Ofast
- From: Jens Alfke <email@hidden>
- Date: Mon, 17 Mar 2014 17:43:44 -0700
On Mar 17, 2014, at 12:06 PM, Fritz Anderson < email@hidden> wrote: However, Apple defaults release builds to -Os (size) for a reason. “Fast” optimizations entail inlining functions that aren’t even declared inline, and unwinding loops into serial repetitions of the loop content. Tricks like that inflate the binary, and make overflows of the processor cache more likely and more frequent. Cache memory can keep up with the CPU; RAM can’t. Faulting the cache costs you more speed than “efficient” code.
+1, in general. But IIRC there’s a new-ish optimization level “-Ofast" in Clang that’s supposed to be smarter about not bloating code size so much. There was a WWDC talk about it last year that might help.
—Jens |
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