Re: [PATCH/RFC] PR target/15130 SH: A tail call optimization

[Kaz Kojima <kkojima at rr dot iij4u dot or dot jp>]

amylaar@spamcop.net (Joern Rennecke) wrote:
>> and replacing 7 with temp in output_stack_adjust calls in
>> sh_expand_epilogue together with the push/pop sequence using
>> r4/r5 in output_stack_adjust for temp < 0 might be ok for 3.3.4.
>> Thoughts?
> 
> This seems to make sense, except that for the last output_stack_adjust call -
> the one after restoring the registers - you have to pass -1 in the sibcall_p
> case.

Ah, I've missed it.  How about the patch below?
I'm running make bootstrap on 3.3 with it.

Regards,
	kaz
--
	* config/sh/sh-protos.h (sh_expand_epilogue): Change prototype.
	* config/sh/sh.c (output_stack_adjust): Generate a special
	push/pop sequence when failing to get a temporary register for
	non SHmedia epilogue.
	(sh_expand_epilogue): Add an argument to show whether it's for
	sibcall or not.  Take the sibcall epilogue into account.
	(sh_need_epilogue): Call sh_expand_epilogue with 0.
	* config/sh/sh.md (sibcall_epilogue): Call sh_expand_epilogue
	with 1.
	(epilogue): Call sh_expand_epilogue with 0.

diff -uprN ORIG/gcc-3.3/gcc/config/sh/sh-protos.h LOCAL/gcc-3.3/gcc/config/sh/sh-protos.h
--- ORIG/gcc-3.3/gcc/config/sh/sh-protos.h	2004-01-13 02:03:24.000000000 +0900
+++ LOCAL/gcc-3.3/gcc/config/sh/sh-protos.h	2004-05-11 10:55:52.000000000 +0900
@@ -118,7 +118,7 @@ extern struct rtx_def *get_fpscr_rtx PAR
 extern void output_file_start PARAMS ((FILE *));
 extern int sh_media_register_for_return PARAMS ((void));
 extern void sh_expand_prologue PARAMS ((void));
-extern void sh_expand_epilogue PARAMS ((void));
+extern void sh_expand_epilogue PARAMS ((bool));
 extern int sh_need_epilogue PARAMS ((void));
 extern int initial_elimination_offset PARAMS ((int, int));
 extern int fldi_ok PARAMS ((void));
diff -uprN ORIG/gcc-3.3/gcc/config/sh/sh.c LOCAL/gcc-3.3/gcc/config/sh/sh.c
--- ORIG/gcc-3.3/gcc/config/sh/sh.c	2004-01-15 03:11:36.000000000 +0900
+++ LOCAL/gcc-3.3/gcc/config/sh/sh.c	2004-05-12 20:35:40.000000000 +0900
@@ -4277,7 +4277,55 @@ output_stack_adjust (size, reg, temp, em
 	     register to MACL.  However, there is currently no need
 	     to handle this case, so just abort when we see it.  */
 	  if (temp < 0)
-	    abort ();
+	    {
+	      /* If we reached here, the most likely case is the (sibcall)
+		 epilogue for non SHmedia.  Put a special push/pop sequence
+		 for such case as the last resort.  This looks lengthy but
+		 would not be problem because it seems to be very rare.  */
+	      if (! TARGET_SHMEDIA && (emit_fn != frame_insn))
+		{
+		  rtx adj_reg, tmp_reg, mem;
+
+		  /* ??? There is still the slight possibility that r4 or r5
+		     have been reserved as fixed registers or assigned as
+		     global registers, and they change during an interrupt.
+		     There are possible ways to handle this:
+		     - If we are adjusting the frame pointer (r14), we can do
+		       with a single temp register and an ordinary push / pop
+		       on the stack.
+		     - Grab any call-used or call-saved registers (i.e. not
+		       fixed or globals) for the temps we need.  We might
+		       also grab r14 if we are adjusting the stack pointer.
+		       If we can't find enough available registers, issue
+		       a diagnostic and abort - the user must have reserved
+		       way too many registers.
+		     But since all this is rather unlikely to happen and
+		     would require extra testing, we just abort if r4 / r5
+		     are not available.  */
+		  if (fixed_regs[4] || fixed_regs[5]
+		      || global_regs[4] || global_regs[5])
+		    abort ();
+
+		  adj_reg = gen_rtx_REG (GET_MODE (reg), 4);
+		  tmp_reg = gen_rtx_REG (GET_MODE (reg), 5);
+		  emit_move_insn (gen_rtx_MEM (Pmode, reg), adj_reg);
+		  emit_insn (GEN_MOV (adj_reg, GEN_INT (size)));
+		  emit_insn (GEN_ADD3 (adj_reg, adj_reg, reg));
+		  mem = gen_rtx_MEM (Pmode, gen_rtx_PRE_DEC (Pmode, adj_reg));
+		  emit_move_insn (mem, tmp_reg);
+		  emit_move_insn (tmp_reg, gen_rtx_MEM (Pmode, reg));
+		  mem = gen_rtx_MEM (Pmode, gen_rtx_PRE_DEC (Pmode, adj_reg));
+		  emit_move_insn (mem, tmp_reg);
+		  emit_move_insn (reg, adj_reg);
+		  mem = gen_rtx_MEM (Pmode, gen_rtx_POST_INC (Pmode, reg));
+		  emit_move_insn (adj_reg, mem);
+		  mem = gen_rtx_MEM (Pmode, gen_rtx_POST_INC (Pmode, reg));
+		  emit_move_insn (tmp_reg, mem);
+		  return;
+		}
+	      else
+		abort ();
+	    }
 	  const_reg = gen_rtx_REG (GET_MODE (reg), temp);
 
 	  /* If SIZE is negative, subtract the positive value.
@@ -4843,7 +4891,7 @@ sh_expand_prologue ()
 }
 
 void
-sh_expand_epilogue ()
+sh_expand_epilogue (bool sibcall_p)
 {
   HOST_WIDE_INT live_regs_mask[(FIRST_PSEUDO_REGISTER + 31) / 32];
   int d, i;
@@ -4851,9 +4899,22 @@ sh_expand_epilogue ()
 
   int save_flags = target_flags;
   int frame_size;
+  int temp;
 
   calc_live_regs (&d, live_regs_mask);
 
+  if (! sibcall_p)
+    temp = 7;
+  else if (TARGET_SHMEDIA)
+    temp = 1;
+  else
+    {
+      for (i = FIRST_GENERAL_REG; i <= LAST_GENERAL_REG; i++)
+	if (TEST_HARD_REG_BIT (live_regs_mask, i))
+	  break;
+      temp = (i <= LAST_GENERAL_REG) ? i : -1;
+    }
+
   if (TARGET_SH5 && d % (STACK_BOUNDARY / BITS_PER_UNIT))
     d_rounding = ((STACK_BOUNDARY / BITS_PER_UNIT)
 		  - d % (STACK_BOUNDARY / BITS_PER_UNIT));
@@ -4862,7 +4923,7 @@ sh_expand_epilogue ()
 
   if (frame_pointer_needed)
     {
-      output_stack_adjust (frame_size, frame_pointer_rtx, 7, emit_insn);
+      output_stack_adjust (frame_size, frame_pointer_rtx, temp, emit_insn);
 
       /* We must avoid moving the stack pointer adjustment past code
 	 which reads from the local frame, else an interrupt could
@@ -4878,7 +4939,7 @@ sh_expand_epilogue ()
 	 occur after the SP adjustment and clobber data in the local
 	 frame.  */
       emit_insn (gen_blockage ());
-      output_stack_adjust (frame_size, stack_pointer_rtx, 7, emit_insn);
+      output_stack_adjust (frame_size, stack_pointer_rtx, temp, emit_insn);
     }
 
   if (SHMEDIA_REGS_STACK_ADJUST ())
@@ -5054,7 +5115,7 @@ sh_expand_epilogue ()
   output_stack_adjust (extra_push + current_function_pretend_args_size
 		       + d + d_rounding
 		       + current_function_args_info.stack_regs * 8,
-		       stack_pointer_rtx, 7, emit_insn);
+		       stack_pointer_rtx, (sibcall_p ? -1 : temp), emit_insn);
 
   /* Switch back to the normal stack if necessary.  */
   if (sp_switch)
@@ -5078,7 +5139,7 @@ sh_need_epilogue ()
       rtx epilogue;
 
       start_sequence ();
-      sh_expand_epilogue ();
+      sh_expand_epilogue (0);
       epilogue = get_insns ();
       end_sequence ();
       sh_need_epilogue_known = (epilogue == NULL ? -1 : 1);
diff -uprN ORIG/gcc-3.3/gcc/config/sh/sh.md LOCAL/gcc-3.3/gcc/config/sh/sh.md
--- ORIG/gcc-3.3/gcc/config/sh/sh.md	2004-01-13 02:03:25.000000000 +0900
+++ LOCAL/gcc-3.3/gcc/config/sh/sh.md	2004-05-11 10:55:52.000000000 +0900
@@ -6414,7 +6414,7 @@
   ""
   "
 {
-  sh_expand_epilogue ();
+  sh_expand_epilogue (1);
   if (TARGET_SHCOMPACT)
     {
       rtx insn, set;
@@ -7158,7 +7158,7 @@
   ""
   "
 {
-  sh_expand_epilogue ();
+  sh_expand_epilogue (0);
   emit_jump_insn (gen_return ());
   DONE;
 }")