x86-64 Archives - IT Nursery

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Why would introducing useless MOV instructions speed up a tight loop in x86_64 assembly?

Background: While optimizing some Pascal code with embedded assembly language, I noticed an unnecessary MOV instruction, and removed it. To my surprise, removing ...

May 26, 2022
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Why does GCC use multiplication by a strange number in implementing integer division?

I’ve been reading about div and mul assembly operations, and I decided to see them in action by writing a simple program in ...

May 22, 2022
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Submit to App Store issues: Unsupported Architecture x86

So I am trying to use the Shopify API. When I archive the app and validate it then there are no issues but ...

May 19, 2022
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How can I determine if a .NET assembly was built for x86 or x64?

I’ve got an arbitrary list of .NET assemblies. I need to programmatically check if each DLL was built for x86 (as opposed to ...

May 11, 2022
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Why does GCC generate 15-20% faster code if I optimize for size instead of speed?

I first noticed in 2009 that GCC (at least on my projects and on my machines) have the tendency to generate noticeably faster ...

May 3, 2022
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How do I achieve the theoretical maximum of 4 FLOPs per cycle?

How can the theoretical peak performance of 4 floating point operations (double precision) per cycle be achieved on a modern x86-64 Intel CPU? ...

April 28, 2022
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What’s the purpose of the LEA instruction?

For me, it just seems like a funky MOV. What’s its purpose and when should I use it? 17 s 17

April 21, 2022
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