5 ms·

It is written in other, more general "specification" called physics Computers arent purely abstract, they exist in real world and are affected by it, so lets d

It is written in other, more general "specification" called physics Computers arent purely abstract, they exist in real world and are affected by it, so lets do not try to pretend otherwise

lpapez 2y ago
Yet the compiler writers care only about the language spec, and you can bet that failing to optimize this as dead code would be considered a compiler bug. This goes not only for Java compiler, but many other languages as well.
- hardware2win 2y ago
  Sometimes compiler engineers try to be too smart and they end up creating a mess :) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8537 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8537 >When optimizing code for "dead store removal" the optimizing compiler may remove code necessary for security.
  - guappa 2y ago
    I'm going to point out that the bug is marked " RESOLVED INVALID "
    - hardware2win 2y ago
      Political thing, but bug created by removal is real :)
      - planede 2y ago
        The bug is real, but it isn't the compiler's.
      - guappa 2y ago
        Well you posted the link… next time at least try to post one that supports your idea instead of the opposite.
thfuran 2y ago
What exactly do you expect an optimizing compiler to do?
- hardware2win 2y ago
  Leave code without obvious side effects alone (this is different from dead code)
  - thfuran 2y ago
    But this is code obviously without side effect.
    - hardware2win 2y ago
      There are side effects, but in real world, not abstract
      - dkersten 2y ago
        So non-obvious side effects? You can say that about any code at all, so no optimising would ever be possible. The program running faster is a side effect after all.
      - thfuran 2y ago
        No, that code has no side effects. The implementation is free to produce whatever side effects it wants or needs as part of execution, but that is absolutely none of the compiler's business.
  - dzaima 2y ago
    What would "leave alone" even be? There's no "default" state of performance of Java code; it would be ridiculously stupid for there to be something saying that, say, "a+b" for int type values has to take at least 1 nanosecond or something. And you can't use big O complexity here either - the int type has a maximum of 2 billion, and thus a loop over it is trivially O(1), just with a potentially-big constant factor. (or, alternatively, the loop was sped up by a constant factor of 2 billion, and optimizing compilers should extremely obviously be allowed to optimize code by a constant factor)
funcDropShadow 2y ago
So according to that "specification" no optimization is allowed. Since that would almost always change the "heating behavior" of code. Therefore, it is absurd.
- thfuran 2y ago
  None at all, even out of order execution. For that matter, executing the same code on different hardware is right out. Every program must be implemented on single-purpose hardware, and you can't even manufacture two of them.

It is written in other, more general "specification" called physics Computers arent purely abstract, they exist in real world and are affected by it, so lets do not try to pretend otherwise

lpapez 2y ago

Yet the compiler writers care only about the language spec, and you can bet that failing to optimize this as dead code would be considered a compiler bug. This goes not only for Java compiler, but many other languages as well.

hardware2win 2y ago
Sometimes compiler engineers try to be too smart and they end up creating a mess :) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8537 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8537 >When optimizing code for "dead store removal" the optimizing compiler may remove code necessary for security.
- guappa 2y ago
  I'm going to point out that the bug is marked " RESOLVED INVALID "
  - hardware2win 2y ago
    Political thing, but bug created by removal is real :)
    - planede 2y ago
      The bug is real, but it isn't the compiler's.
    - guappa 2y ago
      Well you posted the link… next time at least try to post one that supports your idea instead of the opposite.

thfuran 2y ago

What exactly do you expect an optimizing compiler to do?

hardware2win 2y ago
Leave code without obvious side effects alone (this is different from dead code)
- thfuran 2y ago
  But this is code obviously without side effect.
  - hardware2win 2y ago
    There are side effects, but in real world, not abstract
    - dkersten 2y ago
      So non-obvious side effects? You can say that about any code at all, so no optimising would ever be possible. The program running faster is a side effect after all.
    - thfuran 2y ago
      No, that code has no side effects. The implementation is free to produce whatever side effects it wants or needs as part of execution, but that is absolutely none of the compiler's business.
- dzaima 2y ago
  What would "leave alone" even be? There's no "default" state of performance of Java code; it would be ridiculously stupid for there to be something saying that, say, "a+b" for int type values has to take at least 1 nanosecond or something. And you can't use big O complexity here either - the int type has a maximum of 2 billion, and thus a loop over it is trivially O(1), just with a potentially-big constant factor. (or, alternatively, the loop was sped up by a constant factor of 2 billion, and optimizing compilers should extremely obviously be allowed to optimize code by a constant factor)

funcDropShadow 2y ago

So according to that "specification" no optimization is allowed. Since that would almost always change the "heating behavior" of code. Therefore, it is absurd.

thfuran 2y ago
None at all, even out of order execution. For that matter, executing the same code on different hardware is right out. Every program must be implemented on single-purpose hardware, and you can't even manufacture two of them.