https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77644
Bug ID: 77644
Summary: missed optimization with sqrt in comparison
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: Joost.VandeVondele at mat dot ethz.ch
Target Milestone: ---
> cat t.f90
LOGICAL FUNCTION F1(A,B)
REAL :: A,B
F1=(abs(A)<sqrt(B))
END FUNCTION
LOGICAL FUNCTION F2(A,B)
REAL :: A,B
F2=(A*A<B)
END FUNCTION
LOGICAL FUNCTION F3(A,B)
REAL :: A,B
F3=sqrt(A*A)<sqrt(B*B)
END FUNCTION
LOGICAL FUNCTION F4(A,B)
REAL :: A,B
F4=(A*A)<(B*B)
END FUNCTION
In the testcase above F1 could be optimized as F2, F3 as F4, at least with
-ffast-math, getting rid of a sqrt. a<b -> a*a < b*b if a>0 and b>0.
