Programming Languages explained (funny pic)

Magnum said:
Is there any here who could program in assembler?
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I started on the x86. I also did a lot of dis-assembly on the Siemens telecoms processors in the day, including their massive in-house monsters, especially single-stepping through diagnostic programs to localise faults
 
And then you have python...


[video=youtube_share;g3YiPC91QUk]https://youtu.be/g3YiPC91QUk[/video]
 
BTW, any of you still use assembly?

I still do - primarily via intrinsics and to check compiled code quality for performance. Also for specialized hardware.
 
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No, its been a few years since I really worked on any low level code that required assembly (or even C for that matter).

I had a lot of fun when I was young optimising my line rendering assembly code.
 
cguy said:
BTW, any of you still use assembly?

I still do - primarily via intrinsics and to check compiled code quality for performance. Also for specialized hardware.
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Which software do you use and would you perhaps mind elaborating on the bolded part? Thanks :)
 
mercurial said:
Which software do you use and would you perhaps mind elaborating on the bolded part? Thanks :)
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I typically write this type of code in C or C++ and compile it. I will then use something like objdump or a compilation with the -S option to see the assembler source code that was generated. I will then look at the assembler and see if there are any inefficiencies in the code that was generated.

The kind of thing I would look for may be:
- Short pieces of code not being inlined
- The compiler can't tell that there is no overwrite between two reads of a global variable, so it gets read every time
- The compiler runs out of registers within a loop, and spill to the the stack
- The compiler generates many jumps to early out of a compound condition that I will almost always be true
- The compiler may make incorrect assumptions about the likelihood of a condition being true or false
- The compiler may correctly choose the likelihood of a condition being true or false, however, the unlikely case may be the speed sensitive one (and the one I want the CPU speculate)
- Compares and jumps can perhaps be avoided by conditional moves
- Vectorization may have unintended side effects
- Hand vectorization may accelerate a given piece of code
- The compiler may not be able to make assumptions about loop variable sizes, so it generates unnecessary remainder handling code that bloats the code cache as it gets prefetched.
- etc.
 
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