[Bug target/52642] New: SH Target: libstdc++ failures due to call insn swapped before prologue frame insns

["olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52642

             Bug #: 52642
           Summary: SH Target: libstdc++ failures due to call insn swapped
                    before prologue frame insns
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: olegendo@gcc.gnu.org
                CC: kkojima@gcc.gnu.org
            Target: sh*-*-*


Carry over from PR 51244 comment #33 ...

Looking into the libstdc++ failures for sh4-unknown-linux-gnu,
it seems that the call insn was swapped before prologue frame insns
and then it makes unwinder confused.  -fno-delayed-branch also stops
that swapping for these failing cases.  The patch below works for me.

    * config/sh/sh.c (sh_expand_prologue): Emit blockage at the end
    of prologue for unwinder and profiler.

--- ORIG/trunk/gcc/config/sh/sh.c    2012-03-06 10:28:32.000000000 +0900
+++ trunk/gcc/config/sh/sh.c    2012-03-14 20:22:15.000000000 +0900
@@ -7234,6 +7234,13 @@ sh_expand_prologue (void)
       emit_insn (gen_shcompact_incoming_args ());
     }

+  /* If we are profiling, make sure no instructions are scheduled before
+     the call to mcount.  Similarly if some call instructions are swapped
+     before frame related insns, it'll make unwinder confused because
+     currently SH has no unwind info for function epilogues.  */
+  if (crtl->profile || flag_exceptions || flag_unwind_tables)
+    emit_insn (gen_blockage ());
+
   if (flag_stack_usage_info)
     current_function_static_stack_size = stack_usage;
 }