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0 pointsathrun3y ago0 comments

Would it not be in Intel's best interest to have popular compilers be able to squeeze the most performance out of its own line of CPUs?

I'm wondering how the incentives play out to keep this stuff private?

0 comments

userbinator3y ago

Intel sells a compiler. I've only used it briefly a long time ago, but its code generation was well ahead of MSVC at the time even for scalar (non-SIMD) stuff, and I remember GCC was far behind too (it would generate roughly the same performance in microbenchmarks, but far more bloated.)

bee_rider3y ago

Intel has released at least some of their software suite for free (as in beer, not as in speech).

https://www.intel.com/content/www/us/en/developer/articles/n...

I think software is not a huge profit center for them.

The original comment presents:

> The actual details there are [1] too secret for Intel to want to accurately describe them in gcc, [2] they’re different across different CPUs, [3] and compilers just aren’t as good as you think they are.

2 and 3 could just be the whole story. Although we haven't actually accumulated any evidence here for 3, given that the original story was about surprisingly getting beat by a compiler, despite performing a seemingly obvious optimization.

astrange3y ago

You can just look at gcc and llvm source. GCC’s x86 backend is maintained by an Intel employee and it doesn’t have especially detailed descriptions of any cpu in -mtune.

Actually, compiler optimizations like scheduling tend to be neutral to negative on x86 because they increase register pressure. You’d probably want to do “anti-scheduling” and hope the CPU decoder takes care of it if anything.

projektfu3y ago

https://en.wikipedia.org/wiki/Intel_C%2B%2B_Compiler

Interesting that it generates suboptimal code for non-Intel processors.

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