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Rules to avoid common extended inline assembly mistakes

(nullprogram.com)
73 points ingve | 1 comments | 20 Dec 24 20:03 UTC | HN request time: 0.208s | source
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tom_ ◴[21 Dec 24 02:52 UTC] No.42477165[source]▶
It's always been a mystery to me why people put up with this stuff. Adding strings to the assembler output is fine if you want to assemble some unsupported instruction, and a useful getout clause. But as the only option, it sucks, and it's no fun if you want to insert more than 1 instruction.

I used CodeWarrior for PowerPC about 15 years ago, and its inline assembler was very easy to use. No markup required, and you didn't even have to really understand the ABI. Write a C function, add "register" to the parameters, put register variables inside the function, add an asm block inside it, then do your worst. It'd track variable liveness to allocate registers, and rearrange instructions to lengthen dependency chains. Any problems, you'd get an error. Very nice.

replies(4): >>42477331 #>>42477671 #>>42477682 #>>42479166 #
1. Conscat ◴[21 Dec 24 05:07 UTC] No.42477671[source]▶
Raw multi-line R"()" strings in C++ reduce some of the tedium. I wrote myself an Emacs tree sitter pattern to highlight asm syntax nicer than a string normally would, which helps. There is also the stasm library (which I haven't used) that looks like a pleasant syntax. https://github.com/stasinek/stasm

Clang (but not GCC) also supports the MSVC assembly syntax which is derived from Borland inline assembly. Unlike MSVC, Clang supports it in 64-bit mode and also for arm.