-------------------------------------------------
+    The complete source files.
-------------------------------------------------

import std.stdio;

void calculate1(float a, float b)
{
    float s1 = 1.0f - a;
    float s2 = a * b;
    writeln(s2);
    writeln(a * b);
}

void calculate2(float a, float b)
{
    float s1 = 1.0 - a;
    float s2 = a * b;
    writeln(s2);
    writeln(a * b);
}

void calculate3(double a, double b)
{
    double s1 = 1.0 - a;
    double s2 = a * b;
    writeln(s2);
    writeln(a * b);   
}

int main()
{   
    writeln("calculate1:");
    calculate1(0.75f,2.0f);
    writeln("calculate2:");
    calculate2(0.75f,2.0f);
    writeln("calculate3:");
    calculate3(0.75f,2.0f);
    return 0;
}

-------------------------------------------------
+    The complete output
-------------------------------------------------

calculate1:
1.5
1.5
calculate2:
0
1.5
calculate3:
1.5
1.5

-------------------------------------------------
+    Compiler
-------------------------------------------------

DMD64 D Compiler v2.057
Copyright (c) 1999-2011 by Digital Mars written by Walter Bright
Documentation: http://www.digitalmars.com/d/2.0/index.html
Usage:

This is from the downloaded zip file.
I'm using eclipse to compile it. Added the -debug.


-------------------------------------------------
+    Ubuntu 11.10 64 bit
-------------------------------------------------

uname -r
3.0.0-15-generic

-------------------------------------------------
+    BEHAVIOUR
-------------------------------------------------

Seems to work on 32 bit on windows. And also when
you use -inline on the compiler. (even on 64 bit
with inline)

In the previous message here below is the assembly
output of calculate2. Pay close attention to the
cvtss2sd, the cvtsd2ss and the mulss.

    float s1 = 1.0 - a;
    float s2 = a * b;

The first mulss (s2) uses the xmm1 register. Which was
subjected to the cvtss2sd for the (s1) calculation.

-------------------------------------------------
+    objdump -S test1.o
-------------------------------------------------

This is the assembly output of:

void calculate2(float a, float b) 

Warning: mov is from left to right. :-)

0000000000000000 <_D4main10calculate2FffZv>:
   0:    55                       push   %rbp
   1:    48 8b ec                 mov    %rsp,%rbp
   4:    48 83 ec 20              sub    $0x20,%rsp
   8:    f3 0f 11 45 f0           movss  %xmm0,-0x10(%rbp)
   d:    f3 0f 11 4d f8           movss  %xmm1,-0x8(%rbp)
  12:    48 b8 00 00 00 00 00     movabs $0x3ff0000000000000,%rax
  19:    00 f0 3f
  1c:    48 89 45 e0              mov    %rax,-0x20(%rbp)
  20:    f2 0f 10 55 e0           movsd  -0x20(%rbp),%xmm2
  25:    f3 0f 5a c9              cvtss2sd %xmm1,%xmm1
  29:    f2 0f 5c d1              subsd  %xmm1,%xmm2
  2d:    f2 0f 5a d2              cvtsd2ss %xmm2,%xmm2
  31:    f3 0f 59 c8              mulss  %xmm0,%xmm1
  35:    f3 0f 11 4d e8           movss  %xmm1,-0x18(%rbp)
  3a:    f3 0f 10 45 e8           movss  -0x18(%rbp),%xmm0
  3f:    e8 00 00 00 00           callq  44 <_D4main10calculate2FffZv+0x44>
  44:    f3 0f 10 45 f8           movss  -0x8(%rbp),%xmm0
  49:    f3 0f 10 4d f0           movss  -0x10(%rbp),%xmm1
  4e:    f3 0f 59 c1              mulss  %xmm1,%xmm0
  52:    e8 00 00 00 00           callq  57 <_D4main10calculate2FffZv+0x57>
  57:    c9                       leaveq
  58:    c3                       retq
  59:    90                       nop
  5a:    90                       nop
  5b:    90                       nop