How to convert an unsigned integer to floating-point in x86 (32-bit) assembly?

Question

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 integer

Answer 1

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

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 :
   0:   48 85 ff                test   %rdi,%rdi
   3:   78 0b                   js     10 
   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 :
  30:   48 85 ff                test   %rdi,%rdi
  33:   78 0b                   js     40 
  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 :
  60:   89 ff                   mov    %edi,%edi
  62:   c4 e1 fb 2a c7          vcvtsi2sd %rdi,%xmm0,%xmm0
  67:   c3                      retq   

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