intrinsics Questions
2
Solved
In a simd-tutorial i found the following code-snippet.
void simd(float* a, int N)
{
// We assume N % 4 == 0.
int nb_iters = N / 4;
__m128* ptr = reinterpret_cast<__m128*>(a); // (...
Affirmatory asked 18/11, 2019 at 8:59
1
Solved
According to https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html, there's:
type __atomic_load_n (type *ptr, int memorder)
and (the "generic"):
void __atomic_load (type *ptr, type ...
Aglitter asked 29/10, 2019 at 23:46
4
Solved
I've got some code that works with __m128 values. I'm using x86-64 SSE intrinsics on these values and I find that if the values are unaligned in memory I get a crash. This is due to my compiler (cl...
Wealth asked 24/11, 2015 at 9:4
1
Solved
Calling _mm_load_ps returns an __m128. In the Intel intrinsics guide it says:
Load 128-bits (composed of 4 packed single-precision (32-bit) floating-point elements) from memory into dst. mem_add...
Glassman asked 17/10, 2019 at 19:36
2
I was trying to use AVX512 intrinsics to vectorize my loop of matrix multiplication (tiled). I used __mm256d as variables to store intermediate results and store them in my results. However, ...
Demarco asked 30/9, 2019 at 2:40
3
Solved
How does one efficiently perform horizontal addition with floats in a 512-bit AVX register (ie add the items from a single vector together)? For 128 and 256 bit registers this can be done using _mm...
Hardej asked 12/11, 2014 at 20:58
3
Solved
I have a section of code which is a bottleneck in a C++ application running on x86 processors, where we take double values from two arrays, cast to float and store in an array of structs. The reaso...
Bindweed asked 12/7, 2019 at 20:22
3
Solved
Java intrinsic functions are mentioned in various places (e.g. here). My understanding is that these are methods that handled with special native code. This seems similar to a JNI method which is a...
Kliment asked 21/6, 2019 at 7:28
2
Solved
I'm trying to create a minimal reproducer for this issue report. There seems to be some problems with AVX-512, which is shipping on the latest Apple machines with Skylake processors.
According to ...
Tiflis asked 4/12, 2018 at 2:47
1
Solved
I'm pretty new to intrinsics and i faced with different behavior of my code with GCC-7.4 and GCC-8.3
My code is pretty simple
b.cpp:
#include <iostream>
#include <xmmintrin.h>
void ...
Thymelaeaceous asked 10/6, 2019 at 8:47
2
Solved
I was browsing .NET source code and saw this attribute. It says,
An attribute that can be attached to JIT Intrinsic methods/properties
and according to MSDN:
Indicates that a modified metho...
Osteoma asked 13/11, 2014 at 7:58
3
Solved
The code i want to optimize is basically a simple but large arithmetic formula, it should be fairly simple to analyze the code automatically to compute the independent multiplications/additions in ...
Acidify asked 19/9, 2012 at 13:13
2
Solved
I have some code written that uses AVX intrinsics when they are available on the current CPU. In GCC and Clang, unlike Visual C++, in order to use intrinsics, you must enable them on the command li...
Manion asked 11/9, 2017 at 23:37
2
Solved
A quick Google search for "instrinsic attribute c#" only returns articles about other attributes, such as [Serializable]. Apparently these are called "intrinsic attributes".
However, there is als...
Norvol asked 31/5, 2019 at 4:27
1
Solved
I know how to test if an _m128i register is all zero with the _mm_test_all_zeros intrinsic.
What is the AVX2 / __m256i version of this intrinsic? If one isn't available, what is the fastest way to...
Redo asked 28/5, 2019 at 16:24
1
Solved
I need a way to compare values of type __m128i in C++ for a total order between any values of type __m128i. The type of order doesn't matter as long as it establishes a total order between all valu...
Glossal asked 28/5, 2019 at 11:39
1
Solved
If my understanding is correct,
_mm_movehdup_ps(a)
gives the same result as
_mm_shuffle_ps(a, a, _MM_SHUFFLE(1, 1, 3, 3))?
Is there a performance difference the two?
Awash asked 21/5, 2019 at 12:21
1
I'm playing around with .NET Core 3.0's new support for hardware intrinsics, in the System.Runtime.Intrinsics namespace.
I have some code where I perform 4 XOR operations in a loop - below is a si...
Workmanship asked 8/5, 2019 at 8:52
2
Solved
I have some code using the AVX2 intrinsic _mm256_permutevar8x32_epi32 aka vpermd to select integers from an input vector by an index vector. Now I need the same thing but for 4x32 instead of 8x32. ...
Windom asked 8/5, 2019 at 3:58
1
I'm writing some performance sensitive code, where multiplication of unsigned 64-bit integers (ulong) is a bottleneck.
.NET Core 3.0 beings access to hardware intrinsics with the System.Runtime.In...
Perfection asked 7/5, 2019 at 9:23
2
Solved
I wonder how does a Compiler treats Intrinsics.
If one uses SSE2 Intrinsics (Using #include <emmintrin.h>) and compile with -mavx flag. What will the compiler generate? Will it generate AVX ...
Dehumidifier asked 18/4, 2019 at 14:6
1
Solved
AVX512 provide us with intrinsics to sum all cells in a __mm512 vector. However, some of their counterparts are missing: there is no _mm512_reduce_add_epi8, yet.
_mm512_reduce_add_ps //horizontal ...
Alidus asked 22/3, 2019 at 9:41
1
Solved
I'm learning how to use SIMD intrinsics and autovectorization. Luckily, I have a useful project I'm working on that seems extremely amenable to SIMD, but is still tricky for a newbie like me.
I'm...
Salina asked 8/3, 2019 at 6:36
1
I am trying to do a SIMD division in an AVX machine and getting a compilation error.
Here is my code:
__m256i help;
int arr[8];
int arr2[8];
help = _mm256_load_si256((__m256i*)arr);
__m256i ...
Jacqui asked 26/2, 2019 at 16:19
1
Solved
I am testing some of intrinsic operations' behaviors. I got surprised when I noticed that _mm_mfence() issues load instruction from user space, but it does not count in L1 data cache - miss, hit or...
Biestings asked 25/2, 2019 at 23:36
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