如何在x86(32位)程序集中将无符号整数转换为浮点数? [英] How to convert an unsigned integer to floating-point in x86 (32-bit) assembly?

问题描述

我需要将32位和64位无符号整数都转换为xmm寄存器中的浮点值.有x86指令可将有符号整数转换为单精度和双精度浮点值，但对于无符号整数则没有任何说明.

I need to convert both 32-bit and 64-bit unsigned integers into floating-point values in xmm registers. There are x86 instructions to convert signed integers into single and double precision floating-point values, but nothing for unsigned integers.

奖金:如何将xmm寄存器中的浮点值转换为32位和64位无符号整数?

Bonus: How to convert float-point values in xmm registers to 32-bit and 64-bit unsigned integers?

推荐答案

无耻地将Janus答案用作模板(毕竟我真的很喜欢C ++):

Shamelessly using Janus answer as a template (after all I really like C++):

在i7上使用gcc -march=native -O3生成，因此最多包含-mavx. uint2float相反，反之亦然，对于大于2 ⁶³ -1的数字，长转换只是一种特殊情况.

Generate with gcc -march=native -O3 on a i7, so this is with up to and including -mavx. uint2float and vice versa are as expected, the long conversions just have a special case for numbers greater than 2⁶³-1.

0000000000000000 <ulong2double>:
   0:   48 85 ff                test   %rdi,%rdi
   3:   78 0b                   js     10 <ulong2double+0x10>
   5:   c4 e1 fb 2a c7          vcvtsi2sd %rdi,%xmm0,%xmm0
   a:   c3                      retq   
   b:   0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
  10:   48 89 f8                mov    %rdi,%rax
  13:   83 e7 01                and    $0x1,%edi
  16:   48 d1 e8                shr    %rax
  19:   48 09 f8                or     %rdi,%rax
  1c:   c4 e1 fb 2a c0          vcvtsi2sd %rax,%xmm0,%xmm0
  21:   c5 fb 58 c0             vaddsd %xmm0,%xmm0,%xmm0
  25:   c3                      retq   

0000000000000030 <ulong2float>:
  30:   48 85 ff                test   %rdi,%rdi
  33:   78 0b                   js     40 <ulong2float+0x10>
  35:   c4 e1 fa 2a c7          vcvtsi2ss %rdi,%xmm0,%xmm0
  3a:   c3                      retq   
  3b:   0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
  40:   48 89 f8                mov    %rdi,%rax
  43:   83 e7 01                and    $0x1,%edi
  46:   48 d1 e8                shr    %rax
  49:   48 09 f8                or     %rdi,%rax
  4c:   c4 e1 fa 2a c0          vcvtsi2ss %rax,%xmm0,%xmm0
  51:   c5 fa 58 c0             vaddss %xmm0,%xmm0,%xmm0
  55:   c3                      retq   

0000000000000060 <uint2double>:
  60:   89 ff                   mov    %edi,%edi
  62:   c4 e1 fb 2a c7          vcvtsi2sd %rdi,%xmm0,%xmm0
  67:   c3                      retq   

0000000000000070 <uint2float>:
  70:   89 ff                   mov    %edi,%edi
  72:   c4 e1 fa 2a c7          vcvtsi2ss %rdi,%xmm0,%xmm0
  77:   c3                      retq 

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