intrinsics

问题 I have the following problem which I need to solve using anything other than AVX2. I have 3 values stored in a m128i variable (the 4th value is not needed ) and need to shift those values by 4,3,5. I need two functions. One for the right logical shift by those values and another for the left logical shift. Does anyone know a solution to the problem using SSE/AVX ? The only thing I could find was _mm_srlv_epi32() which is AVX2. To add a little more information. Here is the code I am trying to

问题 Microsoft released their ARM64 build tools recently as part of Visual Studio 15.9. I'm finishing a port to ARM64. I'm having trouble with polynomial multiplication. The problem I am having is, Microsoft does not provide the expected data types like poly64_t , or casts like vreinterpretq_u64_p128 . Also see arm64_neon.h on GitHub. This fails to compile: #include <arm64_neon.h> poly128_t VMULL_P64(const poly64_t a, const poly64_t b) { return vmull_p64(a, b); } And the result: test.cxx(2): error

问题 I want to use intrinsics to increment the elements of a SIMD vector. The simplest way seems to be to add 1 to each element, like this: (note: vec_inc has been set to 1 before) vec = _mm256_add_epi16 (vec, vec_inc); but is there any special instruction to increment a vector? Like inc in this page ? Or any other easier way ? 回答1: The INC instruction is not a SIMD level instruction, it operates on integer scalars. As you and Paul already suggested, the simplest way is to add 1 to each vector

问题 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 also a block of native code. What is the difference? 回答1: The JIT knows about intrinsics, so it can inline the relevant machine instruction into the code it's JITing, and optimize around it as part of a hot loop. A JNI function is a 100% black box for the compiler, with significant call/return

问题 GCC compiler provides a set of builtins to test some processor features, like availability of certain instruction sets. But, according to this thread we also may know certain cpu features may be not enabled by OS. So the question is: do __builtin_cpu_supports intrinsics also check if OS has enabled certain processor feature? 回答1: No. I disabled AVX on my Skylake system by adding noxsave to the Linux kernel boot options. When I do cat /proc/cpuinfo AVX (and AVX2) no longer appear and when I

问题 My initial attempt looked like this (supposed we want to multiply) __m128 mat[n]; /* rows */ __m128 vec[n] = {1,1,1,1}; float outvector[n]; for (int row=0;row<n;row++) { for(int k =3; k < 8; k = k+ 4) { __m128 mrow = mat[k]; __m128 v = vec[row]; __m128 sum = _mm_mul_ps(mrow,v); sum= _mm_hadd_ps(sum,sum); /* adds adjacent-two floats */ } _mm_store_ss(&outvector[row],_mm_hadd_ps(sum,sum)); } But this clearly doesn't work. How do I approach this? I should load 4 at a time.... The other question

问题 I am currently experimenting with the creation of highly-optimized, reusable functions for a library of mine. For instance, I write the function "is power of 2" the following way: template<class IntType> inline bool is_power_of_two( const IntType x ) { return (x != 0) && ((x & (x - 1)) == 0); } This is a portable, low-maintenance implementation as an inline C++ template. This code is compiled by VC++ 2008 to the following code with branches: is_power_of_two PROC test rcx, rcx je SHORT $LN3@is

问题 There are many methods in the Java API that are intrinsics, but still have code associated with them when looking at the source code. For an example, Integer.bitCount() is an intrinsic, but if you open the Integer class file, you can see code with it. What purposes might this code serve if it is not necessarily used by the compiler/jvm? 回答1: As per wiki, the definition of Intrinsic Function is as follows: In compiler theory, an intrinsic function is a function available for use in a given

问题 I have the following code which compiles with GCC using the flag -msse4 but the problem is that the pop count only gets the last four 8-bits of the converted __m128i type. Basically what I want is to count all 16 numbers inside the __m128i type but I'm not sure what intrinsic function call to make after creating the variable popA . Somehow popA has to be converted into an integer that contains all the 128-bits of information? I suppose theres _mm_cvtsi128_si64 and using a few shuffle few

问题 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 also an attribute in C# that is itself called [Intrinsic] and I'm trying to figure out what exactly it is and how it works. It doesn't exist on the common attributes page of the .NET Documentation, or anywhere else in the documentation as far as I can see. This attribute is used inside of .NET Core in