[Darwin, PPC] Allow the user to override the use of hard float in kexts.

The default for the kernel is soft-float, however a user writing a kernel
extension might want to make use of hard float.  This change makes
" -mkernel -mhard-float " work as expected.

2019-06-27  Iain Sandoe  <iain@sandoe.co.uk>

	* config/rs6000/rs6000.c (darwin_rs6000_override_options): Honour
	user-specified float mode choice for kernel mode code.

From-SVN: r272760

gcc/ChangeLog

 2019-06-27  Iain Sandoe  <iain@sandoe.co.uk>
 
+	* config/rs6000/rs6000.c (darwin_rs6000_override_options): Honour
+	user-specified float mode choice for kernel mode code.
+
+2019-06-27  Iain Sandoe  <iain@sandoe.co.uk>
+
 	* config/rs6000/darwin.h (ENDFILE_SPEC): Correct whitespace in the
 	spec.
 

gcc/config/rs6000/rs6000.c

@@ -3430,7 +3430,10 @@ darwin_rs6000_override_options (void)
   if (flag_mkernel)
     {
       rs6000_default_long_calls = 1;
-      rs6000_isa_flags |= OPTION_MASK_SOFT_FLOAT;
+
+      /* Allow a kext author to do -mkernel -mhard-float.  */
+      if (! (rs6000_isa_flags_explicit & OPTION_MASK_SOFT_FLOAT))
+        rs6000_isa_flags |= OPTION_MASK_SOFT_FLOAT;
     }
 
   /* Make -m64 imply -maltivec.  Darwin's 64-bit ABI includes