http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56355
Bug #: 56355
Summary: abs and multiplication
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: gli...@gcc.gnu.org
#include <cmath>
#include <cstdlib>
typedef double T;
// typedef int T;
T f(T a, T b){
return std::abs(a)*std::abs(b);
}
T g(T a){
return std::abs(a)*std::abs(a);
}
T h(T a){
return std::abs(a*a);
}
Compiled with g++ -O3 (-ffast-math doesn't help), g is properly optimized to
a*a but only at the RTL level, and the other 2 are not optimized at all. If I
make T a typedef for int, nothing is optimized.
For the first one, I would expect abs(a*b), and for the others just a*a.
Related to PR 31548.
