or1k: Fix clobbering of _mcount argument if fPIC is enabled

Recently we changed the PROFILE_HOOK _mcount call to pass in the link
register as an argument.  This actually does not work when the _mcount
call uses a PLT because the GOT register setup code ends up getting
inserted before the PROFILE_HOOK and clobbers the link register
argument.

These glibc tests are failing:
  gmon/tst-gmon-pie-gprof
  gmon/tst-gmon-static-gprof

This patch fixes this by saving the instruction that stores the Link
Register to the _mcount argument and then inserts the GOT register setup
instructions after that.

For example:

main.c:

    extern int e;

    int f2(int a) {
      return a + e;
    }

    int f1(int a) {
      return f2 (a + a);
    }

    int main(int argc, char ** argv) {
      return f1 (argc);
    }

Compiled:

    or1k-smh-linux-gnu-gcc -Wall -c -O2 -fPIC -pg -S main.c

Before Fix:

    main:
        l.addi  r1, r1, -16
        l.sw    8(r1), r2
        l.sw    0(r1), r16
        l.addi  r2, r1, 16   # Keeping FP, but not needed
        l.sw    4(r1), r18
        l.sw    12(r1), r9
        l.jal   8            # GOT Setup clobbers r9 (Link Register)
         l.movhi        r16, gotpchi(_GLOBAL_OFFSET_TABLE_-4)
        l.ori   r16, r16, gotpclo(_GLOBAL_OFFSET_TABLE_+0)
        l.add   r16, r16, r9
        l.or    r18, r3, r3
        l.or    r3, r9, r9    # This is not the original LR
        l.jal   plt(_mcount)
         l.nop

        l.jal   plt(f1)
         l.or    r3, r18, r18
        l.lwz   r9, 12(r1)
        l.lwz   r16, 0(r1)
        l.lwz   r18, 4(r1)
        l.lwz   r2, 8(r1)
        l.jr    r9
         l.addi  r1, r1, 16

After the fix:

    main:
        l.addi  r1, r1, -12
        l.sw    0(r1), r16
        l.sw    4(r1), r18
        l.sw    8(r1), r9
        l.or    r18, r3, r3
        l.or    r3, r9, r9    # We now have r9 (LR) set early
        l.jal   8             # Clobbers r9 (Link Register)
         l.movhi        r16, gotpchi(_GLOBAL_OFFSET_TABLE_-4)
        l.ori   r16, r16, gotpclo(_GLOBAL_OFFSET_TABLE_+0)
        l.add   r16, r16, r9
        l.jal   plt(_mcount)
         l.nop

        l.jal   plt(f1)
         l.or    r3, r18, r18
        l.lwz   r9, 8(r1)
        l.lwz   r16, 0(r1)
        l.lwz   r18, 4(r1)
        l.jr    r9
         l.addi  r1, r1, 12

Fixes: 308531d148a ("or1k: Add return address argument to _mcount call")

gcc/ChangeLog:
	* config/or1k/or1k-protos.h (or1k_profile_hook): New function.
	* config/or1k/or1k.h (PROFILE_HOOK): Change macro to reference
	new function or1k_profile_hook.
	* config/or1k/or1k.c (struct machine_function): Add new field
	set_mcount_arg_insn.
	(or1k_profile_hook): New function.
	(or1k_init_pic_reg): Update to inject pic rtx after _mcount arg
	when profiling.
	(or1k_frame_pointer_required): Frame pointer no longer needed
	when profiling.

3 files changed, 42 insertions, 16 deletions

diff --git a/gcc/config/or1k/or1k-protos.h b/gcc/config/or1k/or1k-protos.h
index bbb54c8..56554f2 100644
--- a/gcc/config/or1k/or1k-protos.h
+++ b/gcc/config/or1k/or1k-protos.h
@@ -20,6 +20,7 @@ along with GCC; see the file COPYING3.  If not see
 extern HOST_WIDE_INT or1k_initial_elimination_offset (int, int);
 extern void or1k_expand_prologue (void);
 extern void or1k_expand_epilogue (void);
+extern void or1k_profile_hook (void);
 extern void or1k_expand_eh_return (rtx);
 extern rtx  or1k_initial_frame_addr (void);
 extern rtx  or1k_dynamic_chain_addr (rtx);
diff --git a/gcc/config/or1k/or1k.c b/gcc/config/or1k/or1k.c
index 27d3fa1..bb7270c 100644
--- a/gcc/config/or1k/or1k.c
+++ b/gcc/config/or1k/or1k.c
@@ -73,6 +73,10 @@ struct GTY(()) machine_function
 
   /* Remember where the set_got_placeholder is located.  */
   rtx_insn *set_got_insn;
+
+  /* Remember where mcount args are stored so we can insert set_got_insn
+     after.  */
+  rtx_insn *set_mcount_arg_insn;
 };
 
 /* Zero initialization is OK for all current fields.  */
@@ -415,6 +419,25 @@ or1k_expand_epilogue (void)
 			   EH_RETURN_STACKADJ_RTX));
 }
 
+/* Worker for PROFILE_HOOK.
+   The OpenRISC profile hook uses the link register which will get clobbered by
+   the GOT setup RTX.  This sets up a placeholder to allow injecting of the GOT
+   setup RTX to avoid clobbering.  */
+
+void
+or1k_profile_hook (void)
+{
+  rtx a1 = gen_rtx_REG (Pmode, 3);
+  rtx ra = get_hard_reg_initial_val (Pmode, LR_REGNUM);
+  rtx fun = gen_rtx_SYMBOL_REF (Pmode, "_mcount");
+
+  /* Keep track of where we setup the _mcount argument so we can insert the
+     GOT setup RTX after it.  */
+  cfun->machine->set_mcount_arg_insn = emit_move_insn (a1, ra);
+
+  emit_library_call (fun, LCT_NORMAL, VOIDmode, a1, Pmode);
+}
+
 /* Worker for TARGET_INIT_PIC_REG.
    Initialize the cfun->machine->set_got_insn rtx and insert it at the entry
    of the current function.  The rtx is just a temporary placeholder for
@@ -423,17 +446,25 @@ or1k_expand_epilogue (void)
 static void
 or1k_init_pic_reg (void)
 {
-  start_sequence ();
 
-  cfun->machine->set_got_insn
-    = emit_insn (gen_set_got_tmp (pic_offset_table_rtx));
+  if (crtl->profile)
+    cfun->machine->set_got_insn =
+      emit_insn_after (gen_set_got_tmp (pic_offset_table_rtx),
+		       cfun->machine->set_mcount_arg_insn);
+  else
+    {
+      start_sequence ();
+
+      cfun->machine->set_got_insn =
+	emit_insn (gen_set_got_tmp (pic_offset_table_rtx));
 
-  rtx_insn *seq = get_insns ();
-  end_sequence ();
+      rtx_insn *seq = get_insns ();
+      end_sequence ();
 
-  edge entry_edge = single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun));
-  insert_insn_on_edge (seq, entry_edge);
-  commit_one_edge_insertion (entry_edge);
+      edge entry_edge = single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun));
+      insert_insn_on_edge (seq, entry_edge);
+      commit_one_edge_insertion (entry_edge);
+    }
 }
 
 #undef TARGET_INIT_PIC_REG
@@ -480,7 +511,7 @@ or1k_frame_pointer_required ()
 {
   /* ??? While IRA checks accesses_prior_frames, reload does not.
      We do want the frame pointer for this case.  */
-  return (crtl->accesses_prior_frames || crtl->profile);
+  return (crtl->accesses_prior_frames);
 }
 
 /* Expand the "eh_return" pattern.
diff --git a/gcc/config/or1k/or1k.h b/gcc/config/or1k/or1k.h
index 8a529f4..bea7ba4 100644
--- a/gcc/config/or1k/or1k.h
+++ b/gcc/config/or1k/or1k.h
@@ -392,13 +392,7 @@ do {                                                    \
 
 /* Emit rtl for profiling.  Output assembler code to call "_mcount" for
    profiling a function entry.  */
-#define PROFILE_HOOK(LABEL)						\
-  {									\
-    rtx fun, ra;							\
-    ra = get_hard_reg_initial_val (Pmode, LR_REGNUM);			\
-    fun = gen_rtx_SYMBOL_REF (Pmode, "_mcount");			\
-    emit_library_call (fun, LCT_NORMAL, VOIDmode, ra, Pmode);		\
-  }
+#define PROFILE_HOOK(LABEL)  or1k_profile_hook()
 
 /* All the work is done in PROFILE_HOOK, but this is still required.  */
 #define FUNCTION_PROFILER(STREAM, LABELNO) do { } while (0)