Stack Exchange

Peter Cordes

Halifax, Canada

GNU/Linux hacker and command line junkie.

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

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Top Questions
48 votes

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

30 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

29 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

22 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

14 votes

In GNU C inline asm, what're the modifiers for xmm/ymm/zmm for a single operand?

c gcc assembly sse avx512 asked Dec 25 '15 at 3:35
stackoverflow.com

12 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

11 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

11 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

11 votes

Is vxorps-zeroing on AMD Jaguar/Bulldozer/Zen faster with xmm registers than ymm?

assembly x86 avx micro-optimization amd-processor asked May 1 '17 at 1:53
stackoverflow.com

10 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

1 2 3

Top Answers
1829
C++ code for testing the Collatz conjecture faster than hand-written assembly - why?
stackoverflow.com

396
Deoptimizing a program for the pipeline in Intel Sandybridge-family CPUs
stackoverflow.com

271
Does the C++ standard allow for an uninitialized bool to crash a program?
stackoverflow.com

192
What is the best way to set a register to zero in x86 assembly: xor, mov or and?
stackoverflow.com

180
Can num++ be atomic for 'int num'?
stackoverflow.com

121
Why does this delay-loop start to run faster after several iterations with no sleep?
stackoverflow.com

94
Why does my browser think that https://1.1.1.1 is secure?
superuser.com

84
What Every Programmer Should Know About Memory?
stackoverflow.com

68
Boolean values as 8 bit in compilers. Are operations on them inefficient?
stackoverflow.com

68
How to remove “noise” from GCC/clang assembly output?
stackoverflow.com

65
Fastest way to do horizontal float vector sum on x86
stackoverflow.com

62
Why are leap seconds needed so often?
physics.stackexchange.com

61
Where is the lock for a std::atomic?
stackoverflow.com

46
Efficient integer floor function in C++
stackoverflow.com

44
INC instruction vs ADD 1: Does it matter?
stackoverflow.com

43
C loop optimization help for final assignment
stackoverflow.com

43
Why is the Linux kernel 15+ million lines of code?
unix.stackexchange.com

41
Is `~/Documents` a relative or an absolute path?
unix.stackexchange.com

39
Why is std::fill(0) slower than std::fill(1)?
stackoverflow.com

38
Why is pow(int, int) so slow?
stackoverflow.com

37
What is the efficient way to count set bits at a position or lower?
stackoverflow.com

37
Is this floating-point optimization allowed?
stackoverflow.com

36
Where is the x86-64 System V ABI documented?
stackoverflow.com

36
What happens if you use the 32-bit int 0x80 Linux ABI in 64-bit code?
stackoverflow.com

35
Why don't compilers merge redundant std::atomic writes?
stackoverflow.com

34
Fastest way to compute absolute value using SSE
stackoverflow.com

34
Why is 'The Chinese have invented the printer' wrong?
ell.stackexchange.com

34
The start of x86: Intel 8080 vs Intel 8086?
retrocomputing.stackexchange.com

33
Is there anything special about -1 (0xFFFFFFFF) regarding ADC?
stackoverflow.com

33
Fastest way to sort 10 numbers? (numbers are 32 bit)
stackoverflow.com

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