http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52890
Pat Haugen <pthaugen at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |NEW
--- Comment #7 from Pat Haugen <pthaugen at gcc dot gnu.org> 2012-04-11
18:34:55 UTC ---
I observed similar behavior on loads (8-byte loads transformed to sequence of
byte loads/shifts/ors) with r185470, unaligned read patch. This caused some
sizable degradation on a few benchmarks also.-fno-tree-sra had no effect on the
unaligned load case.
Reduced testcase:
// g++ -S -m64 -O2 -mcpu=power7 load.cc
typedef int ggBoolean;
class mrSurface
{
};
template < class T > class ggTrain
{
public:ggBoolean Append (T item);
T operator[] (int i) const
{
return data[i];
}
private: T * data;
int nData;
};
class mrSurfaceList:public mrSurface
{
virtual void viewingHit () const;
protected: ggTrain < mrSurface * >surfaces;
};
extern mrSurface *sPtr;
void
mrSurfaceList::viewingHit () const
{
sPtr = surfaces[1];
}
150r.expand:
D.2562_3 = MEM[(const struct ggTrain *)this_1(D) + 8B];
D.2560_11 = MEM[(struct mrSurface * *)D.2562_3 + 8B];
sPtr = D.2560_11;
The first MEM[...] gets expanded to the sequence of lbzs/shifts/ors.
