On Mon, 30 Jan 2017, Jakub Jelinek wrote: > On Mon, Jan 30, 2017 at 11:47:51AM +0100, Richard Biener wrote: > > On Mon, 30 Jan 2017, Uros Bizjak wrote: > > > > > > 2017-01-30 Richard Biener <rguent...@suse.de> > > > > > > > > PR target/79277 > > > > * config/i386/i386-modes.def: Align DFmode properly. > > > > > > Index: gcc/config/i386/i386-modes.def > > > =================================================================== > > > --- gcc/config/i386/i386-modes.def (revision 245021) > > > +++ gcc/config/i386/i386-modes.def (working copy) > > > @@ -33,6 +33,7 @@ ADJUST_FLOAT_FORMAT (XF, (TARGET_128BIT_ > > > : &ieee_extended_intel_96_format)); > > > ADJUST_BYTESIZE (XF, TARGET_128BIT_LONG_DOUBLE ? 16 : 12); > > > ADJUST_ALIGNMENT (XF, TARGET_128BIT_LONG_DOUBLE ? 16 : 4); > > > +ADJUST_ALIGNMENT (DF, !TARGET_64BIT ? 4 : 8); > > > > > > Please avoid negative logic, just swap arms of the conditional around. > > > > It was just meant as an example fix. I don't think this is appropriate > > at this stage nor is it complete. A full fix would basically make > > x86_field_alignment unnecessary which limits most modes alignment > > to 32bit (but not vector or 128bit float modes). And the conditional > > needs updating to honor TARGET_ALIGN_DOUBLE. > > Yeah, at least for GCC 7 that change (quite major ABI change) is too > dangerous IMHO.
Yes, __alignof__ (double) would change. But I think for correctness at least __alignof__ (*(double *)p) needs to change. So another way to fix this would be to change the FE to use a differently aligned double type in contexts where the default one is wrong (but we do have too many == double_type_node checks everywhere...). Btw, we should eventually change ADJUST_FIELD_ALIGN to take the type of the field instead of the FIELD_DECL (as said, only frv.c looks at the field, all others just look at its type). Richard.
