你能用汇编语言写出代码吗
时间: 2024-03-25 08:37:37 浏览: 15
以下是使用x86汇编语言实现IEEE 754单精度浮点数表示和运算的示例代码:
```assembly
section .data
a_sign dd 0
a_exponent dd 0
a_fraction dd 0
b_sign dd 0
b_exponent dd 0
b_fraction dd 0
result_sign dd 0
result_exponent dd 0
result_fraction dd 0
section .text
global _start
_start:
; 浮点数加法
; a + b
; a: [sign][exponent][fraction]
; b: [sign][exponent][fraction]
; result: [sign][exponent][fraction]
; 返回值存储在result中
; clobbers: eax, ebx, ecx, edx, esi, edi
; 假设浮点数都是规格化的
; 比较指数大小
fld dword [a_exponent]
fld dword [b_exponent]
fucomi st0, st1
jb shift_b
jz add_fractions
shift_a:
; 将a的尾数右移
fld dword [a_fraction]
fmul dword [shift_mask]
fistp dword [a_fraction]
sub dword [a_exponent], 1
cmp dword [a_exponent], 0
jg shift_a
jmp add_fractions
shift_b:
; 将b的尾数右移
fld dword [b_fraction]
fmul dword [shift_mask]
fistp dword [b_fraction]
sub dword [b_exponent], 1
cmp dword [b_exponent], 0
jg shift_b
add_fractions:
; 计算尾数相加结果
fld dword [a_fraction]
fld dword [b_fraction]
faddp st1, st0
; 计算进位
fxch st1
fld1
faddp st1, st0
fcomi st0, dword [fraction_mask]
jb no_carry
fsub dword [fraction_mask], st0
fstp dword [fraction_mask]
add dword [a_exponent], 1
no_carry:
fstp dword [result_fraction]
; 计算指数
mov eax, dword [a_exponent]
mov ebx, dword [b_exponent]
cmp eax, ebx
jge use_a
mov eax, ebx
use_a:
mov dword [result_exponent], eax
; 计算符号
mov eax, dword [a_sign]
xor eax, dword [b_sign]
mov dword [result_sign], eax
; 浮点数减法
; a - b
; a: [sign][exponent][fraction]
; b: [sign][exponent][fraction]
; result: [sign][exponent][fraction]
; 返回值存储在result中
; clobbers: eax, ebx, ecx, edx, esi, edi
; 假设浮点数都是规格化的
mov eax, dword [b_fraction]
not eax
mov dword [temp_fraction], eax
mov eax, dword [b_exponent]
not eax
mov dword [temp_exponent], eax
mov eax, dword [b_sign]
not eax
mov dword [temp_sign], eax
fld dword [temp_sign]
fld dword [temp_exponent]
fld dword [temp_fraction]
fld dword [a_sign]
fld dword [a_exponent]
fld dword [a_fraction]
fxch st3
fucomi st0, st3
jbe swap
fstp st0
fxch st0
swap:
fstp st0
fld dword [result_sign]
fxch st0
fld dword [result_exponent]
fxch st0
fld dword [result_fraction]
fxch st0
fsubp st1, st0
; 计算指数
mov eax, dword [result_fraction]
test eax, 0x800000
jz normalize
add dword [result_exponent], 1
normalize:
cmp dword [result_exponent], 0
jge finish
xor dword [result_sign], 1
mov eax, dword [result_fraction]
test eax, 0xfffff
jnz finish
shr dword [result_fraction], 1
add dword [result_exponent], 1
jmp normalize
finish:
; 浮点数乘法
; a * b
; a: [sign][exponent][fraction]
; b: [sign][exponent][fraction]
; result: [sign][exponent][fraction]
; 返回值存储在result中
; clobbers: eax, ebx, ecx, edx, esi, edi
; 假设浮点数都是规格化的
fld dword [a_fraction]
fld dword [b_fraction]
fmul
fld dword [a_exponent]
fld dword [b_exponent]
fsubp st1, st0
fld1
faddp st1, st0
fistp dword [temp_exponent]
mov eax, dword [temp_exponent]
add eax, 127
mov dword [result_exponent], eax
fld dword [result_exponent]
fld dword [shift_mask]
fmul
fistp dword [temp_shift]
mov ebx, dword [temp_shift]
mov eax, dword [result_fraction]
shl eax, 8
imul dword [b_fraction], dword [a_fraction]
mov esi, eax
mov edi, edx
mov eax, ebx
shr esi, cl
rcl edi, cl
mov dword [result_fraction], esi
; 计算进位
cmp dword [result_fraction], 0x800000
jb no_carry2
add dword [result_exponent], 1
and dword [result_fraction], 0x7fffff
no_carry2:
; 计算符号
mov eax, dword [a_sign]
xor eax, dword [b_sign]
mov dword [result_sign], eax
; 浮点数除法
; a / b
; a: [sign][exponent][fraction]
; b: [sign][exponent][fraction]
; result: [sign][exponent][fraction]
; 返回值存储在result中
; clobbers: eax, ebx, ecx, edx, esi, edi
; 假设浮点数都是规格化的
fld dword [a_fraction]
fld dword [b_fraction]
fdiv
fld dword [a_exponent]
fld dword [b_exponent]
fsubp st1, st0
fld1
faddp st1, st0
fistp dword [temp_exponent]
mov eax, dword [temp_exponent]
add eax, 127
mov dword [result_exponent], eax
fld dword [result_exponent]
fld dword [shift_mask]
fmul
fistp dword [temp_shift]
mov ebx, dword [temp_shift]
mov eax, dword [result_fraction]
shl eax, 8
idiv dword [b_fraction]
mov esi, eax
mov edi, edx
mov eax, ebx
shr esi, cl
rcl edi, cl
mov dword [result_fraction], esi
; 计算进位
cmp dword [result_fraction], 0x800000
jb no_carry3
add dword [result_exponent], 1
and dword [result_fraction], 0x7fffff
no_carry3:
; 计算符号
mov eax, dword [a_sign]
xor eax, dword [b_sign]
mov dword [result_sign], eax
; 退出程序
mov eax, 1
xor ebx, ebx
int 0x80
section .bss
temp_fraction resd 1
temp_exponent resd 1
temp_sign resd 1
temp_shift resd 1
section .rodata
shift_mask dd 0x7f800000
fraction_mask dd 0x00800000
```
以上代码仅为示例,实际应用中需要根据具体情况进行修改和优化。