IBM zSystems: Make stack_tie to work with hard frame pointer

With this patch a scheduling barrier is created to prevent the insn
setting up the frame-pointer and instructions which save GPRs to the
stack to be swapped.  Otherwise broken CFI information would be
generated since the stack save insns would use a base register which
is not currently declared as holding the CFA.

Without -mpreserve-args this did not happen because the store multiple
we used for saving the GPRs would also cover the frame-pointer
register and therefore creates a dependency on the frame-pointer
hardreg. However, with this patch the stack_tie is emitted regardless
of -mpreserve-args since this in general appears to be the safer
approach.

	* config/s390/s390.cc (save_gprs): Use gen_frame_mem.
	(restore_gprs): Likewise.
	(s390_emit_stack_tie): Make the stack_tie to be dependent on the
	frame pointer if a frame-pointer is used.
	(s390_emit_prologue): Emit stack_tie when frame-pointer is needed.
	* config/s390/s390.md (stack_tie): Add a register operand and
	rename to ...
	(@stack_tie<mode>): ... this.

diff --git a/gcc/config/s390/s390.cc b/gcc/config/s390/s390.cc
index a9bb610..4db5677 100644 (file)
--- a/gcc/config/s390/s390.cc
+++ b/gcc/config/s390/s390.cc
@@ -10898,9 +10898,7 @@ save_gprs (rtx base, int offset, int first, int last)
   int i;
 
   addr = plus_constant (Pmode, base, offset);
-  addr = gen_rtx_MEM (Pmode, addr);
-
-  set_mem_alias_set (addr, get_frame_alias_set ());
+  addr = gen_frame_mem (Pmode, addr);
 
   /* Special-case single register.  */
   if (first == last)
@@ -11012,8 +11010,7 @@ restore_gprs (rtx base, int offset, int first, int last)
   rtx addr, insn;
 
   addr = plus_constant (Pmode, base, offset);
-  addr = gen_rtx_MEM (Pmode, addr);
-  set_mem_alias_set (addr, get_frame_alias_set ());
+  addr = gen_frame_mem (Pmode, addr);
 
   /* Special-case single register.  */
   if (first == last)
@@ -11062,10 +11059,11 @@ s390_load_got (void)
 static void
 s390_emit_stack_tie (void)
 {
-  rtx mem = gen_frame_mem (BLKmode,
-                          gen_rtx_REG (Pmode, STACK_POINTER_REGNUM));
-
-  emit_insn (gen_stack_tie (mem));
+  rtx mem = gen_frame_mem (BLKmode, stack_pointer_rtx);
+  if (frame_pointer_needed)
+    emit_insn (gen_stack_tie (Pmode, mem, hard_frame_pointer_rtx));
+  else
+    emit_insn (gen_stack_tie (Pmode, mem, stack_pointer_rtx));
 }
 
 /* Copy GPRS into FPR save slots.  */
@@ -11676,6 +11674,7 @@ s390_emit_prologue (void)
 
   if (frame_pointer_needed)
     {
+      s390_emit_stack_tie ();
       insn = emit_move_insn (hard_frame_pointer_rtx, stack_pointer_rtx);
       RTX_FRAME_RELATED_P (insn) = 1;
     }

diff --git a/gcc/config/s390/s390.md b/gcc/config/s390/s390.md
index 4828aa0..00d3960 100644 (file)
--- a/gcc/config/s390/s390.md
+++ b/gcc/config/s390/s390.md
@@ -11590,9 +11590,10 @@
 ; This is used in s390_emit_prologue in order to prevent insns
 ; adjusting the stack pointer to be moved over insns writing stack
 ; slots using a copy of the stack pointer in a different register.
-(define_insn "stack_tie"
+(define_insn "@stack_tie<mode>"
   [(set (match_operand:BLK 0 "memory_operand" "+m")
-        (unspec:BLK [(match_dup 0)] UNSPEC_TIE))]
+        (unspec:BLK [(match_dup 0)
+                    (match_operand:P 1 "register_operand" "r")] UNSPEC_TIE))]
   ""
   ""
   [(set_attr "length" "0")])