This is a secondary account that sees the most usage. My first account is listed below. The main will have a list of all the accounts that I use.

henfredemars@lemmy.world

Personal website:

https://henfred.me/

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  • 110 Comments
Joined 1 year ago
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Cake day: July 4th, 2023

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  • Call it a difference of opinion that I don’t believe it should try to be bit-accurate for floating point. But, it’s a valid position to take. There are many use cases for QEMU. In this case where we emit some host instructions I do believe it’s still within the helper function instead of inline which is not ideal. The guest code using floating point in the first place to me implies some degree of inaccuracy is permissible and this is the position that some cross architecture game emulators take. But again, I suppose it can depend what code you wish to run.


  • Yes indeed. I develop QEMU at work mainly implementation of new hardware as needed for my employer. It has a software emulator, but it’s not very good. It’s acceptable.

    The instruction generation backend does not seem to prioritize performance. Instead, it prioritizes accuracy and ease of maintenance. There is low-hanging fruit for making it faster but there isn’t much interest in doing so for the TCG backend. The attitude seems to be that it’s good enough.

    For a small example, you may find it interesting that QEMU does not implement floating point acceleration. It’s done in software even though the host has floating point instructions. It usually doesn’t attempt to use those floating point hardware facilities on the host and instead execute many hundreds of instructions to do floating point using the Berkeley software implementation. Almost never does this matter but it costs a lot of performance. Compare this to the translation performed by projects like FEX and Box64 which do and blow QEMU out of the water for specific use cases.

    Another place in the emulator that could be improved is handling of executable pages or cached output of the backend code generator. The executable code caching mechanism is very simple and could probably be much more aggressive on today’s systems.

    If you examine change logs, TCG really doesn’t get much TLC last time I checked. It could be a better emulator but performance outside of KVM use case is not as important to the project.





  • I’d like to add that there’s a difference between unsafe and unspecified behavior. Sometimes I’d like the compiler to produce my unsafe code that has specified behavior. In this case, I want the compiler to produce exactly that unsafe behavior that was specified according to the language semantics.

    Especially when developing a kernel or in an embedded system, an example would be code that references a pointer from a hardcoded constant address. Perhaps this code then performs pointer arithmetic to access other addresses. It’s clear what the code should literally do, but it’s quite an unsafe thing to do unless you as the developer have some special knowledge that you know the address is accessible and contains data that makes sense to be processed in such a manner. This can be the case when interacting directly with registers representing some physical device or peripheral, but of course, there’s nothing in the language that would suggest doing this is safe. It’s making dangerous assumptions that are not enforced as part of the program. Those assumptions are only true in the program is running on the hardware that makes this a valid thing to do, where that magical address and offsets to that address do represent something I can read in memory.

    Of course, pointer arithmetic can be quite dangerous, but I think the point still stands that behavior can be specified and unsafe in a sense.






  • So they support widespread access to free birth control and contraception resources, especially to disadvantaged women everywhere, right? Because if your problem is the abortion itself wouldn’t you want to do everything in your power to prevent it, including preventing pregnancy in the first place as an alternative to what you perceive as murder? Why wouldn’t you fight the same battle through compassion instead of oppression?

    Are you telling me that you’re all in for extensive social programs to support single mothers and provide a strong viable alternative in situations where the mother feels financially incapable of supporting her child? Free childcare perhaps? Reducing the cost of childbearing? There are many peaceful options that are quite thoroughly documented to reduce the number of abortions that could be deployed immediately at a reasonable cost. Yet, you’re not interested in using any of these.

    Alas, these same organizations also seem to be against contraception, childcare, or generally anything that supports the health of the mother and child. This is where you can see their true colors; they don’t want to prevent abortions. That’s a lie, else they would’ve taken many alternative actions that can achieve the same goal. Instead, they choose the course that oppresses women.

    This is the epitome of a bad faith argument. Those who would tell you that abortion is genocide do not believe in their own claim.