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

[Nick Clifton]

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 ?

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