RE: [GD-Windows] forcing value to bool 'true' or 'false' (performance warning)

[Jon W. <hp...@mi...>]

It's more than that. The problem is that any bytes in the int must 
count towards a "true" value. The re-write you propose will generate 
a branch, which will not predict well, which is a REALLY bad thing.

Perhaps MSVC7 generates CMOV for this; I've never gotten MSVC 6 to 
do it unfortunately :-( Another branchless alternative (assuming 
they're OK with any non-0 value for "true" inside a bool, which may 
not be true) is to do some shifts and ors.

  int i; bool b;

  unsigned short temp16 = (i>>16) | i;
  *(unsigned char *)&b = (temp16>>8) | temp16; // horrible!

Cheers,

				/ h+

> Well, the compiler will generate code to convert an int (4 bytes) to a
> bool (usually 1 byte), whether or not it matters for performance is
> dubious.
> 
> You can eliminate the warning by doing 'bool p = i ? true : false;'