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Subject: [Bug middle-end/47990] Missed promotion of double precision constants to single precision for -funsafe-math-optimizations
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47990

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-08-01 13:07:00 UTC ---
The intel compiler does not perform this optimization even at -fast.  It does
perform the demotion on

float foo (float x, float y)
{
  return (int)((float)(x/y + 0.5)) * y;
}

though, even with default optimization (also with the conversion to
int removed or associated to apply to the first operand of the
multiplication only).

So they leave alone what looks like a usual "rounding" pattern.

My original idea was to fold (int)((double)(x/y) + 0.5) to (int)(x/y + 0.5f),
similar to (float)((double)(x/y) + 0.5) to (x/y + 0.5f) which we already
do (at -O0, in convert_to_real).