[s390] Fix some epilogue CFA notes

[Richard Sandiford]

This patch fixes the CFA notes used when an epilogue restores a GPR from
an FPR.  It also makes sure that s390_optimize_prologue preserves the
CFA information.

Tested in the same way as the previous patch.  OK to install?

Thanks,
Richard


gcc/
        * config/s390/s390.c (s390_restore_gprs_from_fprs): Add REG_CFA_RESTORE
        notes to each restore.  Also add REG_CFA_DEF_CFA when restoring %r15.
        (s390_optimize_prologue): Don't clear RTX_FRAME_RELATED_P.  Update the
        REG_CFA_RESTORE list when deciding not to restore a register.

Index: gcc/config/s390/s390.c
===================================================================
--- gcc/config/s390/s390.c      2014-01-31 17:20:31.582196663 +0000
+++ gcc/config/s390/s390.c      2014-02-04 11:15:41.085329442 +0000
@@ -8603,11 +8603,11 @@ s390_restore_gprs_from_fprs (void)
            emit_move_insn (gen_rtx_REG (DImode, i),
                            gen_rtx_REG (DImode, cfun_gpr_save_slot (i)));
          df_set_regs_ever_live (i, true);
-         /* The frame related flag is only required on the save
-            operations.  We nevertheless set it also for the restore
-            in order to recognize these instructions in
-            s390_optimize_prologue.  The flag will then be
-            deleted.  */
+         add_reg_note (insn, REG_CFA_RESTORE, gen_rtx_REG (DImode, i));
+         if (i == STACK_POINTER_REGNUM)
+           add_reg_note (insn, REG_CFA_DEF_CFA,
+                         plus_constant (Pmode, stack_pointer_rtx,
+                                        STACK_POINTER_OFFSET));
          RTX_FRAME_RELATED_P (insn) = 1;
        }
     }
@@ -10847,12 +10847,6 @@ s390_optimize_prologue (void)
              || call_really_used_regs[gpr_regno])
            continue;
 
-         /* For restores we have to revert the frame related flag
-            since no debug info is supposed to be generated for
-            these.  */
-         if (dest_regno == gpr_regno)
-           RTX_FRAME_RELATED_P (insn) = 0;
-
          /* It must not happen that what we once saved in an FPR now
             needs a stack slot.  */
          gcc_assert (cfun_gpr_save_slot (gpr_regno) != -1);
@@ -10935,8 +10929,6 @@ s390_optimize_prologue (void)
          if (GET_CODE (base) != REG || off < 0)
            continue;
 
-         RTX_FRAME_RELATED_P (insn) = 0;
-
          if (cfun_frame_layout.first_restore_gpr != -1
              && (cfun_frame_layout.first_restore_gpr < first
                  || cfun_frame_layout.last_restore_gpr > last))
@@ -10954,8 +10946,19 @@ s390_optimize_prologue (void)
                                              - first) * UNITS_PER_LONG,
                                       cfun_frame_layout.first_restore_gpr,
                                       cfun_frame_layout.last_restore_gpr);
-             RTX_FRAME_RELATED_P (new_insn) = 0;
+
+             /* Remove REG_CFA_RESTOREs for registers that we no
+                longer need to save.  */
+             REG_NOTES (new_insn) = REG_NOTES (insn);
+             for (rtx *ptr = &REG_NOTES (new_insn); *ptr; )
+               if (REG_NOTE_KIND (*ptr) == REG_CFA_RESTORE
+                   && ((int) REGNO (XEXP (*ptr, 0))
+                       < cfun_frame_layout.first_restore_gpr))
+                 *ptr = XEXP (*ptr, 1);
+               else
+                 ptr = &XEXP (*ptr, 1);
              new_insn = emit_insn_before (new_insn, insn);
+             RTX_FRAME_RELATED_P (new_insn) = 1;
              INSN_ADDRESSES_NEW (new_insn, -1);
            }
 
@@ -10977,8 +10980,6 @@ s390_optimize_prologue (void)
          if (GET_CODE (base) != REG || off < 0)
            continue;
 
-         RTX_FRAME_RELATED_P (insn) = 0;
-
          if (REGNO (base) != STACK_POINTER_REGNUM
              && REGNO (base) != HARD_FRAME_POINTER_REGNUM)
            continue;