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I heard Niklaus Wirth would only allow new compiler optimizations (in his compilers for Pascal, Oberson, Modula-2) that proved themselves by speeding up the com

I heard Niklaus Wirth would only allow new compiler optimizations (in his compilers for Pascal, Oberson, Modula-2) that proved themselves by speeding up the compiler itself.

aseipp 7y ago
This is the mandatory rule for Chez Scheme which was only broken once when their entire backend was rewritten, and also (from what I have heard) a large guiding principle for the C# compiler at Microsoft. It's extreme but it's a good idea because it treats compilation time like an actual budget, which it is. You can't just add things endlessly. But it's not easy to achieve in practice.
pizlonator 7y ago
Hahaha that sounds excessive! JavaScriptCore does it differently: many of our benchmarks are either interpreters or compilers written in JavaScript. One of those benchmarks, Air, is just the stack slot coloring phase of JSC’s FTL JIT (that JIT has >90 phases) rewritten in JavaScript instead of C++. It runs like 50x slower in JS than C++ even in JSC, which wins on that test. So, probably it won’t be possible to write a JS VM in JS anytime soon. I mean, surely it’ll be possible, but it’ll also be hilariously shitty.
KMag 7y ago
The specific metric, IIRC, is self-compilation of the compiler. Adding optimizations to the compiler needed to speed up compilation of the compiler more than their added complexity slowed down compilation of the compiler.
bluGill 7y ago
Which might or might not be a good idea. When I'm writing code at my desk the faster it builds the better. I just need my unit tests to finish and they are small. When it the same code running on my embedded system with lots of data being thrown at it in real time and the cpu load is near (sometimes over) 100% I'll take every optimization of the final code I can get no matter how long it takes to build. It would be nice if a gcc replacement compiler made speed of building code the goal. I'll even accept speed of building the compiler after it was compiled with gcc (clang, msvc...) as the benchmark if that is faster.

I heard Niklaus Wirth would only allow new compiler optimizations (in his compilers for Pascal, Oberson, Modula-2) that proved themselves by speeding up the compiler itself.

aseipp 7y ago

This is the mandatory rule for Chez Scheme which was only broken once when their entire backend was rewritten, and also (from what I have heard) a large guiding principle for the C# compiler at Microsoft. It's extreme but it's a good idea because it treats compilation time like an actual budget, which it is. You can't just add things endlessly. But it's not easy to achieve in practice.

pizlonator 7y ago

Hahaha that sounds excessive! JavaScriptCore does it differently: many of our benchmarks are either interpreters or compilers written in JavaScript. One of those benchmarks, Air, is just the stack slot coloring phase of JSC’s FTL JIT (that JIT has >90 phases) rewritten in JavaScript instead of C++. It runs like 50x slower in JS than C++ even in JSC, which wins on that test. So, probably it won’t be possible to write a JS VM in JS anytime soon. I mean, surely it’ll be possible, but it’ll also be hilariously shitty.

KMag 7y ago

The specific metric, IIRC, is self-compilation of the compiler. Adding optimizations to the compiler needed to speed up compilation of the compiler more than their added complexity slowed down compilation of the compiler.

bluGill 7y ago

Which might or might not be a good idea. When I'm writing code at my desk the faster it builds the better. I just need my unit tests to finish and they are small. When it the same code running on my embedded system with lots of data being thrown at it in real time and the cpu load is near (sometimes over) 100% I'll take every optimization of the final code I can get no matter how long it takes to build. It would be nice if a gcc replacement compiler made speed of building code the goal. I'll even accept speed of building the compiler after it was compiled with gcc (clang, msvc...) as the benchmark if that is faster.