Peter Cordes

Halifax, Canada

GNU/Linux hacker and command line junkie.

(profile pic is from https://xkcd.com/386/)

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Why is the loop instruction slow? Couldn't Intel have implemented it efficiently?

performance assembly x86 intel cpu-architecture asked Mar 2 '16 at 9:01

stackoverflow.com

59 votes

What happens if you use the 32-bit int 0x80 Linux ABI in 64-bit code?

linux assembly x86-64 system-calls abi asked Sep 7 '17 at 4:20

stackoverflow.com

44 votes

How exactly do partial registers on Haswell/Skylake perform? Writing AL seems to have a false dependency on RAX, and AH is inconsistent

assembly x86 intel cpu-architecture micro-optimization asked Aug 13 '17 at 12:05

stackoverflow.com

30 votes

What are the best instruction sequences to generate vector constants on the fly?

assembly x86 sse simd avx asked Jan 29 '16 at 12:52

stackoverflow.com

22 votes

Per-element atomicity of vector load/store and gather/scatter?

x86 atomic sse avx avx512 asked Sep 2 '17 at 9:56

stackoverflow.com

16 votes

In GNU C inline asm, what are the size-override modifiers for xmm/ymm/zmm for a single operand?

c gcc sse inline-assembly avx512 asked Dec 25 '15 at 3:35

stackoverflow.com

15 votes

Vectorizing with unaligned buffers: using VMASKMOVPS: generating a mask from a misalignment count? Or not using that insn at all

gcc assembly x86 sse avx asked Dec 16 '15 at 8:16

stackoverflow.com

15 votes

Which 2's complement integer operations can be used without zeroing high bits in the inputs, if only the low part of the result is wanted?

assembly binary x86 integer twos-complement asked Dec 20 '15 at 3:34

stackoverflow.com

14 votes

Does modern PC video hardware support VGA text mode in HW, or does the BIOS emulate it (with System Management Mode)?

performance assembly x86-16 bios vga asked Apr 30 '20 at 10:57

stackoverflow.com

13 votes

ffmpeg: explicitly tag h.264 as bt.601, rather than leaving unspecified?

ffmpeg h.264 colorspace metadata asked Nov 7 '15 at 21:36

video.stackexchange.com

Top Answers

2010

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224

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219

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Can x86's MOV really be "free"? Why can't I reproduce this at all?

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Peter Cordes

Why is the loop instruction slow? Couldn't Intel have implemented it efficiently?

What happens if you use the 32-bit int 0x80 Linux ABI in 64-bit code?

How exactly do partial registers on Haswell/Skylake perform? Writing AL seems to have a false dependency on RAX, and AH is inconsistent

What are the best instruction sequences to generate vector constants on the fly?

Per-element atomicity of vector load/store and gather/scatter?

In GNU C inline asm, what are the size-override modifiers for xmm/ymm/zmm for a single operand?

Vectorizing with unaligned buffers: using VMASKMOVPS: generating a mask from a misalignment count? Or not using that insn at all

Which 2's complement integer operations can be used without zeroing high bits in the inputs, if only the low part of the result is wanted?

Does modern PC video hardware support VGA text mode in HW, or does the BIOS emulate it (with System Management Mode)?

ffmpeg: explicitly tag h.264 as bt.601, rather than leaving unspecified?