RFA: Fix ICE compiling gcc.dg/lto/pr55113_0.c for x86/x86_64

[Richard Biener]

On December 18, 2015 6:29:10 PM GMT+01:00, Nick Clifton <nickc@redhat.com> wrote:
>Hi Guys,
>
>  The gcc test gcc.dg/lto/pr55113_0.c is currently generating an ICE
>  when compiled for x86 and x86_64 targets using the mainline sources
>  (revision 231805):
>
><built-in>: internal compiler error: in layout_type, at
>stor-layout.c:2212
>0xaee2c9 layout_type(tree_node*)
>	/work/sources/gcc/current/gcc/stor-layout.c:2211
>0xd9637b make_vector_type
>	/work/sources/gcc/current/gcc/tree.c:9858
>0xde6cbd ix86_get_builtin_type
>	/work/sources/gcc/current/gcc/config/i386/i386.c:29504
>0xde6d90 ix86_get_builtin_func_type
>
>  The problem is that the test enables -fshort-doubles, but the
>  ix86_get_builtin_func_type still uses the long doubles for the vector
>  modes of the builtin types.  These long doubles have a larger
>  alignment requirement than their short double equivalents, which
>  eventually results in the assertion in stor-layout.c being triggered.
>
>  The patch below is a fix for this problem, although I am not sure if
>  it is the correct fix.  The patch selects the corresponding SFmode
>  variant of the DFmode vector type when flag_short_doubles is enabled.
> Maybe a better patch would be to disallow these builtins when using an
>  ABI breaking option ?
>
>  Checked with no regressions on an x86_64-pc-linux-gnu toolchain.
>
>  OK to apply ?

I think the option should be simply removed...

>Cheers
>  Nick
>
>gcc/ChangeLog
>2015-12-18  Nick Clifton  <nickc@redhat.com>
>
>	* config/i386/i386.c (ix86_get_builtin_type): Use SFmode variant
>	of DFmode vector types when -fshort-doubles is enabled.
>
>Index: gcc/config/i386/i386.c
>===================================================================
>--- gcc/config/i386/i386.c	(revision 231805)
>+++ gcc/config/i386/i386.c	(working copy)
>@@ -29501,6 +29501,17 @@
>    itype = ix86_get_builtin_type (ix86_builtin_type_vect_base[index]);
>       mode = ix86_builtin_type_vect_mode[index];
> 
>+      if (flag_short_double)
>+	{
>+	  switch (mode)
>+	    {
>+	    case V2DFmode: mode = V2SFmode; break;
>+	    case V4DFmode: mode = V4SFmode; break;
>+	    case V8DFmode: mode = V8SFmode; break;
>+	    default: break;
>+	    }
>+	}
>+	    
>       type = build_vector_type_for_mode (itype, mode);
>     }
>   else