[Bug c++/45221] New: missed optimization on casting pointers even under -O3

[navin dot kumar at gmail dot com]

Even under -O3, the assembly generated for foo1 and foo2 is vastly inferior to
the one generated for foo3, even though code-wise all three are identical.


class Base1 { int data; };
class Base2 { int data; };
class Derived : public Base1, public Base2 { public: int data; };

int foo1(Base2* x) {
    return static_cast<Derived&>(*x).data;
}

int foo2(Base2* x) {
    return static_cast<Derived*>(x)->data;
}

int foo3(Base2* x) {
    Base2& y = *x;
    return static_cast<Derived&>(y).data;
}


-- 
           Summary: missed optimization on casting pointers even under -O3
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: navin dot kumar at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45221