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Post Ap6REj8VDZHCL86dDE by [email protected] |
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More posts by [email protected] |
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Post #Ap6Lgv25yqYbcVAWp6 by [email protected] |
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today in completely normal codegen: this code divides by 0x32 |
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Post #Ap6LiCUWYVEo3Y4qbQ by [email protected] |
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multiplicative identity! |
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Post #Ap6NLbEyZXQU3w9hiq by [email protected] |
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@whitequark dividing by 50 never looked so hard. |
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Post #Ap6P11eXNPlro1Qem0 by [email protected] |
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@whitequark Just glancing over it makes my head hurt 😣 |
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Post #Ap6PBvX8T7WA0pAI5Y by [email protected] |
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@whitequark I understand multiplying by 2^x/50 and taking the result from RDX (… |
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Post #Ap6PvLfg8TZM6mosMa by [email protected] |
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@whitequark try using different constants to suicide by; this is a special case… |
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Post #Ap6Q84cQqamYzCMvLM by [email protected] |
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@robryk i have no idea, i'm just reverse-engineering this |
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Post #Ap6QFusWwgQr5rdduS by [email protected] |
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@whitequark of I remember by the time I'm home in the evening I will get go… |
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Post #Ap6QKOsTLrZJIBkWPo by [email protected] |
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@whitequark oh wow modular arithmetic trickery. I've also seen versions of… |
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Post #Ap6QpcK1PqLfxyWLVA by [email protected] |
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@robryk fwiw this was emitted by msvc |
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Post #Ap6REj8VDZHCL86dDE by [email protected] |
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@whitequark I'll add this to my collection. I like to remind my students th… |
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Post #Ap6Yf1JYx8u5vYlQWG by [email protected] |
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@pointingdevice @whitequark That's pretty much what this is? Or, at least, … |
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Post #Ap6Yf1TUMEqMQLPLzU by [email protected] |
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@sabik @whitequark Yes, but I don’t understand the significance of that numbe… |
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Post #Ap6Yf1cLpHvsrpYQnw by [email protected] |
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@sabik @whitequark On a second look, the fact that the result is 32 bits (and m… |
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Post #Ap6Yf1jnNbt5Ev2NPM by [email protected] |
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@pointingdevice @sabik should be unsigned as this is a count/length |
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Post #Ap6jlIAUIsC7QniEN6 by [email protected] |
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@whitequark @pointingdevice @sabik Compilers will use a multiplicative inverse … |
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Post #Ap6klEkl6GrunIDQ24 by [email protected] |
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@whitequark I think this unintentionally explains some disassembly I see in 809… |
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Post #Ap6muYacuwHCpZ32qe by [email protected] |
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@pkhuong @whitequark @pointingdevice @sabik Yep, this is it! And in this case t… |
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Post #Ap6muYhiUZwpBYMhto by [email protected] |
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@typeswitch @pkhuong @pointingdevice @sabik you might be amused by knowing that… |
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Post #Ap6qTK0lPYl9c9XgJs by [email protected] |
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@whitequark Divide A (0-255) by 50:lsr asta templsr alsr alsr aadc tempror alsr… |
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Post #Ap72gGLJYqBPS25krw by [email protected] |
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@whitequark All compilers I've seen can do this optimization. See for examp… |
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Post #Ap79jqn1CyVz2Lhxdg by [email protected] |
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@0x10f aaaaaa i'm getting 8051 flashbacks |
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Post #Ap7HdJsdS1fErkjS76 by [email protected] |
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@whitequark writing code like this is called job security |
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Post #Ap7HgcOb4ERZ9xFrFo by [email protected] |
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@chx this code was written by a compiler |
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Post #Ap7PVewk2i0pWCVkW0 by [email protected] |
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@whitequark this doesn’t seem cursed at all to me. I guess I’m too close to… |
