内联汇编AT&T

#include<stdio.h>

double x = 1.2345678;
double y = 2.3456789;
double z;
double fun(double *a, double *b){
    return *a + *b;
}

int main(){

    __asm__ (
        "movq %1, %%rdi;"
        "movq %2, %%rsi;"
        "call fun;"
        "movq %%xmm0, %0;" 
        // The arguments of fun are not double but double *and return is double,so the xmm0 is return register.
        :"=r"(z)
        :"r"(&x),"r"(&y) //address of x and y are reference arguments.
        : "rax","rdi","rsi"
    );
    printf("%lf\n",z);

}

#include<stdio.h>
/*
double fun(double x, double y){
    double retur;
    __asm__ (
        "movsd %1, %%xmm0\n\t"
        "movsd %2, %%xmm1\n\t"
        "addsd %%xmm1, %%xmm0\n\t"
        "movsd %%xmm0, %0\n\t"
        :"=m"(retur)       
        :"m"(x),"m"(y)    
        :"%xmm0","%xmm1","memory"
    );
    return retur;
} */

double fun(double x, double y){
    double z;
    __asm__ (
        "movsd %1, %%xmm0\n\t"
        "movsd %2, %%xmm1\n\t"
        "addsd %%xmm1, %%xmm0\n\t"
        "movsd %%xmm0, %0\n\t"
        "movq  %0, %%rax\n\t"
        :"=m"(z)       
        :"m"(x),"m"(y)
        :"%xmm0","%xmm1","memory"
    );
}

int main(){
    double x =1.11111;
    double y =2.22222;
    double z=fun(x,y);
    printf("%lf\n",z);
    return 0;   
}
/*
The instruction set "movss or movsd" only move data between xmm and memory, 
but cannot between xmm and general purpose register.
so constraint condition must be"
:"m"(x),"m"(y)
:"=m"(retur)
*/

#include<stdio.h>
/*  method one.
long long fun(long long a, long long b){
    long long result;
    __asm__ (
        "movq %1, %%rax;"
        "movq %2, %%rbx\n\t"
        "addq %%rbx, %%rax;"
        "movq %%rax, %0\n\t"
        : "=r"(result)
        : "r"(a), "r"(b)
        : "%rax", "%rbx"
    );
    return result;
} */
// method two.
long long fun(long long a, long long b){
    __asm__ (
        "movq %1, %%rax;" //both ; and \n\t are Ok for endl.
        "movq %2, %%rbx;"
        "addq %%rbx, %%rax\n\t"
        : "=r"(a)     // this line is only for defining constraint condition completely!
        : "r"(a), "m"(b)
        : "%rax", "%rbx"
    );
}

int main(){
    long long x = 10343434400L;
    long long y = 300454544545L;
    long long z = fun(x, y);
    printf("%lld\n",z);
    return 0;
}

makefile

# 定义编译器和链接器
CXX := g++
CC := gcc
AS := as
LD_GOLD := gold

# 定义编译选项
CXXFLAGS := -Wall -O2
CFLAGS := -Wall -O2
ASFLAGS :=

# 定义链接选项
LDFLAGS :=

# 自动寻找所有的源文件
CPP_SRCS := $(wildcard *.cpp)
C_SRCS := $(wildcard *.c)
S_SRCS := $(wildcard *.s)

# 生成目标文件名
CPP_ELFS := $(patsubst %.cpp,%.elf,$(CPP_SRCS))
C_ELFS := $(patsubst %.c,%.elf,$(C_SRCS))
S_ELFS := $(patsubst %.s,%.elf,$(S_SRCS))

# 默认目标
all: $(CPP_ELFS) $(C_ELFS) $(S_ELFS)

# C++ 文件的编译和链接规则
%.elf: %.cpp
	$(CXX) $(CXXFLAGS) $< -c -o $(patsubst %.elf,%.o,$@)
	$(CXX) $(patsubst %.elf,%.o,$@) -o $@

# C 文件的编译和链接规则
%.elf: %.c
	$(CC) $(CFLAGS) $< -c -o $(patsubst %.elf,%.o,$@)
	$(CC) $(patsubst %.elf,%.o,$@) -o $@

# 汇编文件的编译和链接规则，使用gold
%.elf: %.s
	$(AS) $(ASFLAGS) $< -o $(patsubst %.elf,%.o,$@)
	$(LD_GOLD) $(patsubst %.elf,%.o,$@) -o $@

# 清理构建产物
clean:
	rm -f *.o *.elf

.PHONY: all clean