mmx

问题 I am contemplating an implementation of SHA3 in pure assembly. SHA3 has an internal state of 17 64 bit unsigned integers, but because of the transformations it uses, the best case could be achieved if I had 44 such integers available in the registers. Plus one scratch register possibly. In such a case, I would be able to do the entire transform in the registers. But this is unrealistic, and optimisation is possible all the way down to even just a few registers. Still, more is potentially

问题 In AT&T syntax instructions often have to be suffixed with the appropriate operand size, with q for operations on 64-bit operands. However in MMX and SSE there is also movq instruction, with the q being in the original Intel mnemonic and not an additional suffix. So how will this be represented in AT&T? Is another q suffix needed like movqq %mm1, %mm0 movqq %xmm1, %xmm0 or not? And if there are any other instructions that end like AT&T suffixes (like paddd , slld ), do they work the same way?

问题 In AT&T syntax instructions often have to be suffixed with the appropriate operand size, with q for operations on 64-bit operands. However in MMX and SSE there is also movq instruction, with the q being in the original Intel mnemonic and not an additional suffix. So how will this be represented in AT&T? Is another q suffix needed like movqq %mm1, %mm0 movqq %xmm1, %xmm0 or not? And if there are any other instructions that end like AT&T suffixes (like paddd , slld ), do they work the same way?

问题 I have an inline assembler loop that cumulatively adds elements from an int32 data array with MMX instructions. In particular, it uses the fact that the MMX registers can accommodate 16 int32s to calculate 16 different cumulative sums in parallel. I would now like to convert this piece of code to MMX intrinsics but I am afraid that I will suffer a performance penalty because one cannot explicitly intruct the compiler to use the 8 MMX registers to accomulate 16 independent sums. Can anybody

问题 I have an inline assembler loop that cumulatively adds elements from an int32 data array with MMX instructions. In particular, it uses the fact that the MMX registers can accommodate 16 int32s to calculate 16 different cumulative sums in parallel. I would now like to convert this piece of code to MMX intrinsics but I am afraid that I will suffer a performance penalty because one cannot explicitly intruct the compiler to use the 8 MMX registers to accomulate 16 independent sums. Can anybody

问题 I understand converting MMX 32bit mmx intrinsics no longer allows the __m64. So I was having great trouble upgrading this piece of code to SSE. I was told on another stack-Overflow post to post my code. Perhaps this exercise will help others as well. I commented out '_mm_empty' thinking that was the right thing to do. I found like functions in the emmintrin.h for all the other __m128i opertions, but something is still wrong. original 32-bit function code: DWORD CSumInsideHorizontalTask:

问题 I have a use case, where I have array of bits each bit is represented as 8 bit integer for example uint8_t data[] = {0,1,0,1,0,1,0,1}; I want to create a single integer by extracting only lsb of each value. I know that using int _mm_movemask_pi8 (__m64 a) function I can create a mask but this intrinsic only takes a msb of a byte not lsb. Is there a similar intrinsic or efficient method to extract lsb to create single 8 bit integer? 回答1: There is no direct way to do it, but obviously you can

问题 I've been working on something and run into another couple of problems. First off: ROR64 macro a, rot ; Result := (A shl (64-rot)) xor (A shr rot); MOV EAX, 64 SUB EAX, rot PSLLQ a, EAX MOVQ mm6, a PSRLQ mm6, rot PXOR a, mm6 endm I've been attempting the process using QWords per the last question (I'll probably attempt it with DWords to learn, too). All I have access to on the dev machine I'm using is MMX instructions, so I've been going there. The problem has been handling the values that

问题 I'm trying to create C# app which uses dll library which contains C++ code and inline assembly. In function test_MMX I want to add two arrays of specific length. extern "C" __declspec(dllexport) void __stdcall test_MMX(int *first_array,int *second_array,int length) { __asm { mov ecx,length; mov esi,first_array; shr ecx,1; mov edi,second_array; label: movq mm0,QWORD PTR[esi]; paddd mm0,QWORD PTR[edi]; add edi,8; movq QWORD PTR[esi],mm0; add esi,8; dec ecx; jnz label; } } After run app it's

问题 While I was looking for MMX functions, I noticed that two of them, _m_empty and _mm_empty , have exactly the same definition. So why do they both exist ? Is one of them older than the other ? Is there a difference that is not mentioned in the manual ? 回答1: Differences would/should be pointed out in the documentation. The MSDN is more precise. They explicitly mention this: A synonym for _mm_empty is _m_empty . 来源： https://stackoverflow.com/questions/32413644/what-is-the-difference-between-m