intel

问题 I'm currently trying to figure out the way to produce equivalent assembly code from corresponding c source file. (pardon me for not being able to speak English fluently, I'm new to English.) I've been using C language for several years, but have little experience to assembly language. I was able to output the assembly code using S option in gcc. However, the resulted assembly code contained call instruction which in turn makes a jump to another functions like _exp . This is not what I wanted,

问题 Since OpenMP 4.0, user-defined reduction is supported. So I defined the reduction on std::vector in C++ exactly from here. It works fine with GNU/5.4.0 and GNU/6.4.0, but it returns random values for the reduction with intel/2018.1.163. This is the example: #include <iostream> #include <vector> #include <algorithm> #include "omp.h" #pragma omp declare reduction(vec_double_plus : std::vector<double> : \ std::transform(omp_out.begin(), omp_out.end(), omp_in.begin(), omp_out.begin(), std::plus

问题 I wish to perform integer arithmetic operations on Quad Word elements of the zmm 0-31 register set and preserve the carry bit resulting from those operations. It appears this is only possible if the data were worked on in the general register set. Thus I would like to copy information from one of the zmm 0-31 registers to one of the general purpose registers. After working on the 64 bit data in the general purpose register, I would like to return the data to the original zmm 0-31 register in

问题 I follow this document and using perf record with --intr-regs=ax,bx,r15 , trying to log additional CPU register information with PEBS record. But how do I view those info from perf.data? The original command is perf report , and it only shows a few fields such as overhead, command, shared object and symbol. Is there any way to show CPU regs' value? 回答1: Try perf script data dumping command with the iregs field: perf script -F ip,sym,iregs . All fields -F are documented with source code of

问题 I follow this document and using perf record with --intr-regs=ax,bx,r15 , trying to log additional CPU register information with PEBS record. But how do I view those info from perf.data? The original command is perf report , and it only shows a few fields such as overhead, command, shared object and symbol. Is there any way to show CPU regs' value? 回答1: Try perf script data dumping command with the iregs field: perf script -F ip,sym,iregs . All fields -F are documented with source code of

问题 From the speech Herb Sutter in the figure of the slides on page 2: https://skydrive.live.com/view.aspx?resid=4E86B0CF20EF15AD!24884&app=WordPdf&wdo=2&authkey=!AMtj_EflYn2507c Here are shown separate cache- L1S and Store Buffer ( SB ). 1. In processors Intel x86 cache-L1 and Store Buffer - is the same thing? And next slide: As we see from the next slide in the x86 is only possible following reordering. was: MOV eax, [memory1] / / read MOV [memory2], edx / / write ... / / MOV, MFENCE, ADD ...

问题 This question already has answers here : How to get the CPU cycle count in x86_64 from C++? (4 answers) Closed last year . I have successfully written some inline assembler in gcc to rotate right one bit following some nice instructions: http://www.cs.dartmouth.edu/~sergey/cs108/2009/gcc-inline-asm.pdf Here's an example: static inline int ror(int v) { asm ("ror %0;" :"=r"(v) /* output */ :"0"(v) /* input */ ); return v; } However, I want code to count clock cycles, and have seen some in the

问题 I have done some reading about Spectre v2 and obviously you get the non technical explanations. Peter Cordes has a more in-depth explanation but it doesn't fully address a few details. Note: I have never performed a Spectre v2 attack so I do not have hands on experience. I have only read up about about the theory. My understanding of Spectre v2 is that you make an indirect branch mispredict for instance if (input < data.size) . If the Indirect Target Array (which I'm not too sure of the

问题 I have done some reading about Spectre v2 and obviously you get the non technical explanations. Peter Cordes has a more in-depth explanation but it doesn't fully address a few details. Note: I have never performed a Spectre v2 attack so I do not have hands on experience. I have only read up about about the theory. My understanding of Spectre v2 is that you make an indirect branch mispredict for instance if (input < data.size) . If the Indirect Target Array (which I'm not too sure of the

问题 Concerning the following small code, which was illustrated in another post about the size of structure and all the possibilities to align data correctly : struct { char Data1; short Data2; int Data3; char Data4; } x; unsigned fun ( void ) { x.Data1=1; x.Data2=2; x.Data3=3; x.Data4=4; return(sizeof(x)); } I get the corresponding disassembly (with 64 bits) 0000000000000000 <fun>: 0: 55 push %rbp 1: 48 89 e5 mov %rsp,%rbp 4: c6 05 00 00 00 00 01 movb $0x1,0x0(%rip) # b <fun+0xb> b: 66 c7 05 00