RFA: Fix PR 68028: LTO error when compiling PowerPC binaries with single precision floating point

[Nick Clifton]

Hi Segher,

  OK, here is an official submission of my patch to fix PR 68028.

  I should note that Richard Guenther feels that there is a better way
  to solve the problem - by only initializing the values once - but I
  still like my solution, so I am offering it here.

  OK to apply ?

Cheers
  Nick

gcc/ChangeLog
2018-02-08  Nick Clifton  <ni...@redhat.com>

        * config/rs6000/rs6000.c (rs6000_option_override_internal):
        In LTO mode prefer function attributes over command line -mcpu
        setting.

Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c  (revision 257282)
+++ gcc/config/rs6000/rs6000.c  (working copy)
@@ -4834,12 +4834,25 @@
 
   if (main_target_opt)
     {
-      if (main_target_opt->x_rs6000_single_float != rs6000_single_float)
-       error ("target attribute or pragma changes single precision floating "
-              "point");
-      if (main_target_opt->x_rs6000_double_float != rs6000_double_float)
-       error ("target attribute or pragma changes double precision floating "
-              "point");
+      /* PR 68028: In LTO mode the -mcpu value is passed in as a function
+        attribute rather than on the command line.  So instead of checking
+        for discrepancioes, we enforce the choice determined by the
+        attributes.  */
+        if (in_lto_p)
+          {
+            rs6000_single_float = main_target_opt->x_rs6000_single_float;
+            rs6000_double_float = main_target_opt->x_rs6000_double_float;
+          }
+        /* There could be an 'else' statement here but it is hardly worth
+           it as the compiler will make the optimization anyway, and this
+           way we avoid indenting the code unnecessarily.  */
+
+        if (main_target_opt->x_rs6000_single_float != rs6000_single_float)
+          error ("target attribute or pragma changes single precision floating 
"
+                     "point");
+        if (main_target_opt->x_rs6000_double_float != rs6000_double_float)
+          error ("target attribute or pragma changes double precision floating 
"
+                 "point");
     }
 
   rs6000_always_hint = (rs6000_tune != PROCESSOR_POWER4