http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53094
--- Comment #9 from vincenzo Innocente <vincenzo.innocente at cern dot ch> 2012-12-03 19:15:09 UTC --- adding it "helps" t = build_constructor (TREE_TYPE (t), n); + if (TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE) + t = fold (t); TREE_CONSTANT (t) = true; unfortunately generates ICE for the class constructor at cp/tree.c:2712 struct Rot3 { typedef float T; typedef V4 Vec; Vec axis[3]; constexpr Rot3( V4 ix, V4 iy, V4 iz) : axis{ix,iy,iz}{} constexpr Rot3(T xx, T xy, T xz, T yx, T yy, T yz, T zx, T zy, T zz) : Rot3( (Vec){xx,xy,xz,0}, (Vec){yx,yy,yz,0}, (Vec){zx,zy,zz,0} ){} }; constexpr Rot3 r2( (V4){0, 1 ,0,0}, (V4){0, 0, 1,0},(V4){1, 0, 0,0}); constexpr Rot3 r1( 0, 1 ,0, 0, 0, 1, 1, 0, 0); ceVec.cc:26:46: in constexpr expansion of ‘((Rot3*)(& r1))->Rot3::Rot3(0.0, 1.0e+0, 0.0, 0.0, 0.0, 1.0e+0, 1.0e+0, 0.0, 0.0)’ ceVec.cc:21:4: in constexpr expansion of ‘((Rot3*)this)->Rot3::Rot3(Rot3::Vec{xx, xy, xz, 0.0f}, Rot3::Vec{yx, yy, yz, 0.0f}, Rot3::Vec{zx, zy, zz, 0.0f})’ ceVec.cc:26:46: internal compiler error: in cp_tree_equal, at cp/tree.c:2712 constexpr Rot3 r1( 0, 1 ,0, 0, 0, 1, 1, 0, 0);