x86

问题 I got these GCC flags from the GNU GCC compiler Manual. But when I tried to use those flags ( -mpc32 , -mpc64 and -mpc80 ) I couldn't observe the behavior. So I need help on how to use these flags with a sample code. sample code I tried: test.cpp #include<stdio.h> #include<iomanip> #include<math.h> int main() { double weight = 1.0f; double roiSize = 137.142364501953125f; double thresholdValue = 5400.0f; double alpha = weight / (roiSize * thresholdValue * thresholdValue); std::cout<<std:

问题 I got these GCC flags from the GNU GCC compiler Manual. But when I tried to use those flags ( -mpc32 , -mpc64 and -mpc80 ) I couldn't observe the behavior. So I need help on how to use these flags with a sample code. sample code I tried: test.cpp #include<stdio.h> #include<iomanip> #include<math.h> int main() { double weight = 1.0f; double roiSize = 137.142364501953125f; double thresholdValue = 5400.0f; double alpha = weight / (roiSize * thresholdValue * thresholdValue); std::cout<<std:

问题 I got these GCC flags from the GNU GCC compiler Manual. But when I tried to use those flags ( -mpc32 , -mpc64 and -mpc80 ) I couldn't observe the behavior. So I need help on how to use these flags with a sample code. sample code I tried: test.cpp #include<stdio.h> #include<iomanip> #include<math.h> int main() { double weight = 1.0f; double roiSize = 137.142364501953125f; double thresholdValue = 5400.0f; double alpha = weight / (roiSize * thresholdValue * thresholdValue); std::cout<<std:

问题 I am developing my Operating System. I got error on booting my OS. The error was: KERNEL.BIN not found! Here are the Codes: Boot.asm ; The Aqua_Seven_OS Operating System bootloader ; ================================================================== BITS 16 jmp short bootloader_start ; Jump past disk description section nop ; Pad out before disk description ; ------------------------------------------------------------------ ; Disk description table, to make it a valid floppy ; Note: some of

问题 In assmebly the square brackets seem to have the same meaning as * in C. They are used to dereference a pointer. Dereferencing a pointer means going to refer to a specific memory location to read or write it. So it is quite logical to use square brackets in the case of a MOV. But what is the logical reason why they also use it for LEA. LEA EAX, [EBP -4], looks like dereferencing a pointer, ebp - 4, to refer to the pointed memory location but it will not read the value contained in the

问题 I'm wondering why the instruction FYL2XP1 on x86-architecture computes exactly the mathematical formula y · log 2 ( x + 1). What's special with this formula? 回答1: The y operand is usually a compile time constant, for the moment forget about the x + 1 . Since log_b(x) = log_b(2) * log_2(x) the instruction allows to compute the logarithm in any base of x + 1 . Note that log_b(2) is a constant since it is seldom necessary to compute the logarithm with a degree of freedom in the base. FYL2XP1 and

问题 I want to find the minimum/maximum value into an array of byte using SIMD operations. So far I was able to go through the array and store the minimum/maximum value into a __m128i variable, but it means that the value I am looking for is mixed among others (15 others to be exact). I've found these discussions here and here for integer, and this page for float, but I don't understand how works _mm_shuffle*. So my questions are: What SIMD operations do I have to perform in order to extract the

问题 I want to find the minimum/maximum value into an array of byte using SIMD operations. So far I was able to go through the array and store the minimum/maximum value into a __m128i variable, but it means that the value I am looking for is mixed among others (15 others to be exact). I've found these discussions here and here for integer, and this page for float, but I don't understand how works _mm_shuffle*. So my questions are: What SIMD operations do I have to perform in order to extract the

问题 I've been searching all over for an explanation of how exactly BIOS works now for quite some time. I have designed a bootloader and have jumped to 32-bit mode with it while successfully initializing the IDT as well as the GDT, but in doing so, I have found "operating systems" seeming to be quite simple, and the feeling as if "BIOS" IS the actual operating system of every computer. So now I have took on a new challenge of trying to discover how BIOS actually initializes itself, discovers how

问题 I've been searching all over for an explanation of how exactly BIOS works now for quite some time. I have designed a bootloader and have jumped to 32-bit mode with it while successfully initializing the IDT as well as the GDT, but in doing so, I have found "operating systems" seeming to be quite simple, and the feeling as if "BIOS" IS the actual operating system of every computer. So now I have took on a new challenge of trying to discover how BIOS actually initializes itself, discovers how