MacPorts clang performance (and arm_runtime)

Craig Treleaven ctreleaven at
Sat Dec 20 11:01:41 PST 2014

At 7:17 PM +0100 12/20/14, René J.V. Bertin wrote:
>Some of you may remember that I've wondered 
>aloud in the past why MacPorts clang (3.4) was 
>considerably slower than all other compilers, 
>while the Apple-provided almost-the-same clang 
>3.4 was considerably faster, in line with claims 
>about clang performance. Same for clang-3.4 on 
>Linux (i.e. not Apple provided): it is faster 
>than gcc.
>Just now I noticed a possible explanation:
>>   port variants llvm-3.6
>>  llvm-3.6 has the variants:
>>  [+]assertions: Enable assertions for error detection (has performance
>>  impacts, especially on JIT)
>So the default variant, and the only one 
>available as a binary package, is built to be 
>slow and crash upon certain errors.

Re the speed impact, it would be easy enough to 
install with -assertions and do A-B tests to 
quantitfy the difference.

Related, but an aside...the ability to have 
multiple versions installed and switch among them 
with port activate/deactivate is brilliant.  :)


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