Review-C language Inline compilation-Beginner (1)

Print Hello World and change the value of the variable i

1# include <stdio.h>2 3 intMain ()4 {5         inti =0;6 __asm__ (7                 "mov%0, #4 \ n"8:"=r"(i)//Output9://inputTen:"R0"           //Protection One         ); Aprintf"Hello world!%d\n", i); -}

Note: mov can upload an immediate number to the register, you can pass the value of one register to another register, but you cannot deal with memory, dealing with memory generally with LDR,STR.

The eighth line explains: "=r"-----------------> Register with the output portion, the output is also available.

"=&r"------------------> only use the output section, input is not for anyone.

"+r"---------------------> Input and output are used, for beginners generally use this.

The Tenth Line of Protection section: First __asm__ (...); This statement is embedded in the C language and is treated as an instruction; protection is the state before the R0, that is, the state before the __asm__, and the program is ultimately to be run by the Assembly, __asm__ (); R0 before? The protection is this R0, but __asm__ (...); It can also be used, such as before the R0 is 100,asm instructions or 100, midway with can be used casually.

Simple subtraction.

1#include <stdio.h>2 3 intMain ()4 {5         inti =Ten;6         intj = -;7         intsum =0;8         //sum = i + j;9 __asm__ (Ten                 "add%0,%1,%2\n" One:"=r"(sum)//Output A:"R"(i),"R"(j)//input -         ); -         //Sub%0,%2,%1 the         //Mul%0,%1,%2 -printf"sum%d\n", sum); -}

Simply do a comparison

1#include <stdio.h>2 3 intMain ()4 {5         inti = the;6         intj = -;7         intsum =0;8 #if09         if(I >j)Tensum =i; One         Else Asum =J; - #endif - __asm__ ( the                 "cmp%1,%2\n" -                 "movgt%0,%1\n" -                 "Movle%0,%2\n" -:"=r"(sum)//Output +:"R"(i),"R"(j)//input -         ); +printf"sum%d\n", sum); A}

Description: GT---------------->

Lt----------------<

GE---------------->=

Le----------------<=

EQ----------------= =

ne! ----------------      !=

Simple accumulation and

1#include <stdio.h>2 3 intMain ()4 {5         inti =1;6         intsum =0;7 8 #if09 Bunfly:Tensum = sum +i; Onei++; A         if(i = = -) -                 Gotohaha; -         GotoBunfly; the haha: -          - #else - __asm__ ( +                 "mov%0, #0 \ n" -                 "mov%1, #1 \ n" +                 "bunfly:\n" A                 "add%0,%0,%1\n" at                 "add%1,%1, #1 \ n" -                 "cmp%1, #100 \ n" -                 "beq haha\n" -                 "bne bunfly\n" -                 "haha:\n" -  in:"=&r"(sum)//Output -:"R"(i)//input to         ); + #endif -  theprintf"sum%d\n", sum); *}

Description: Assembler function can refer to the above C language is easy to understand the meaning of the Assembly, it should be noted that 19, 202 lines of initialization and 29 lines of "=&r".

These programs are re-tiny4412 the board running, of course using cross-compiling, example: ARM-NONE-LINUX-GNUEABI-GCC 4.c-o 4

Review-C language Inline compilation-Beginner (1)