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Two-off code in program that runs in about 0.25 seconds
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Robert Prins
Apr 16, 2023, 7:23:01 AM4/16/23
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Current code, simplified:
mov ecx, 10
cdq
div ecx
cdq
div ecx
Equivalent faster, but longer code:
imul eax, 0xcccd
shr eax, 19
imul eax, 0xcccd
shr eax, 19
And yes, as EAX is guaranteed to be small (<= 200) it is equivalent!
Should I really care, or not? And what would a modern compiler generate?
Robert
--
Robert AH Prins
robert(a)prino(d)org
The hitchhiking grandfather - https://prino.neocities.org/
Some REXX code for use on z/OS - https://prino.neocities.org/zOS/zOS-Tools.html
mov ecx, 10
cdq
div ecx
cdq
div ecx
Equivalent faster, but longer code:
imul eax, 0xcccd
shr eax, 19
imul eax, 0xcccd
shr eax, 19
And yes, as EAX is guaranteed to be small (<= 200) it is equivalent!
Should I really care, or not? And what would a modern compiler generate?
Robert
--
Robert AH Prins
robert(a)prino(d)org
The hitchhiking grandfather - https://prino.neocities.org/
Some REXX code for use on z/OS - https://prino.neocities.org/zOS/zOS-Tools.html
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