Chris Jones wrote:

>> GCC vs. clang comparisons on sites like Phoronix suggest that GCC still has
>> the upper hand compared even to clang 4.0 in computation-intensive tasks so
>> it would make a lot of sense to get it to support the full instruction set.
> Please provide links to support such a claim. 

Ok, I should have written "seems to have the upper hand ... in many computation-
intensive tasks".

> My reading is the
> comparison is far from as clear cut as you make out. For instance
> OK, thats from january, with a prelease gcc 7 version. Its the newest I
> have found though...

I've seen the same test, and yes, it's not a clear-cut situation. Those 
tests usually seem to lack a comprehensive summary that doesn't require staring 
hard at a table like 

Clang 3.9.1:         12  [25.0%]
Clang 4.0 SVN:       9   [18.8%]
GCC 4.9.4:           7   [14.6%]
GCC 7.0.0 20170108:  7   [14.6%]
GCC 5.4.0:           7   [14.6%]
GCC 6.3.0:           6   [12.5%]

Clang 3.9.1:         13  [27.1%]
GCC 5.4.0:           12  [25.0%]
GCC 4.9.4:           7   [14.6%]
GCC 7.0.0 20170108:  7   [14.6%]
Clang 4.0 SVN:       7   [14.6%]
GCC 6.3.0:           2   [4.2%]

Either way, benchmarks like these are rarely representative of real-world 
performance in *[y]our* workloads. My own experience over the years has been 
that GCC gives measurably better performance and that in cases where every last 
drop doesn't count you were better off using clang because it compiled so much 
faster. The differences have been disappearing but clang still doesn't win 
across the board with a clear advance.

That's enough for me in itself as an argument to try to make GCC integrate and 
perform as well as possible on Mac, because some users might benefit. Hence my 
interest in support for the AVX (and newer) instruction sets.


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