The following Fortran program
program test
complex :: z
real :: r
r = abs(z)**2
print *, r
end program test
produces the following tree:
D.1352 = __builtin_cabsf (z);
D.1353 = D.1352 * D.1352;
r = D.1353;
The complex value is naively calculated as:
sqrt( (_Real_ z)*(_Real_ z) + (_Imag_ z)*(_Imag_ z) )
However, since the value is squared afterwards, the square root can be simply
removed.
Calculating |...|^2 is not that uncommon in some codes.
--
Summary: __builtin_cabsf(z) squared should be optimized
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: burnus at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31548
