[gcc r12-2639] MMIX: remove generic placeholders parameters in call insn patterns.

[Hans-Peter Nilsson <hp@gcc.gnu.org>]

https://gcc.gnu.org/g:5b2515f5ae86c21fc13021e1a8728a48e68aa7d6

commit r12-2639-g5b2515f5ae86c21fc13021e1a8728a48e68aa7d6
Author: Hans-Peter Nilsson <hp@bitrange.com>
Date:   Sun Jul 18 04:59:30 2021 +0200

    MMIX: remove generic placeholders parameters in call insn patterns.
    
    I guess the best way to describe these operands, at least for MMIX, is
    "ballast".  Some targets seem to drag along one or two of the incoming
    pattern operands through the rtl passes and not dropping them until
    assembly output.  Let's stop doing that for MMIX.  There really are
    *two* unused parameters: one is a number corresponding to the
    stack-size of arguments as a const_int and the other is whatever the
    target yields for targetm.calls.function_arg (args_so_far,
    function_arg_info::end_marker ()).  There's a mandatory second
    argument to the "call" RTX, but the target doesn't have to keep it a
    variable number; it can be replaced by (const_int 0) early, like this.
    
    Astute readers may object that as the MMIX call-type insns (PUSHJ,
    PUSHGO) have a parameter in addition to the address of the called
    function, so should the emitted RTL.  But, that parameter depends only
    on the local function, not the called function (IOW, it's the same for
    all calls in a function), and its value isn't known until frame layout
    time.  Having it a parameter in the emitted RTL for the call would
    just be confusing.  (Maybe this will be amended later, if/when
    improving "shrink-wrapping".)
    
    gcc:
            * config/mmix/mmix.md ("call", "call_value", "*call_real")
            ("*call_value_real"): Don't generate rtx mentioning the generic
            operands 1 and 2 to "call", and similarly for "call_value".
            * config/mmix/mmix.c (mmix_print_operand_punct_valid_p)
            (mmix_print_operand): Use '!' instead of 'p'.

Diff:
---
 gcc/config/mmix/mmix.c  | 20 +++++++++---------
 gcc/config/mmix/mmix.md | 56 ++++++++++++++++++++-----------------------------
 2 files changed, 33 insertions(+), 43 deletions(-)

diff --git a/gcc/config/mmix/mmix.c b/gcc/config/mmix/mmix.c
index db7af7b75b6..010cd4773ea 100644
--- a/gcc/config/mmix/mmix.c
+++ b/gcc/config/mmix/mmix.c
@@ -1624,6 +1624,12 @@ mmix_print_operand (FILE *stream, rtx x, int code)
       fprintf (stream, "%d", MMIX_POP_ARGUMENT ());
       return;
 
+    case '!':
+      /* The number of registers we want to save.  This was setup by the
+	 prologue.  */
+      fprintf (stream, "%d", cfun->machine->highest_saved_stack_register + 1);
+      return;
+
     case 'B':
       if (GET_CODE (x) != CONST_INT)
 	fatal_insn ("MMIX Internal: Expected a CONST_INT, not this", x);
@@ -1712,15 +1718,6 @@ mmix_print_operand (FILE *stream, rtx x, int code)
 	       (int64_t) (mmix_intval (x) - 1));
       return;
 
-    case 'p':
-      /* Store the number of registers we want to save.  This was setup
-	 by the prologue.  The actual operand contains the number of
-	 registers to pass, but we don't use it currently.  Anyway, we
-	 need to output the number of saved registers here.  */
-      fprintf (stream, "%d",
-	       cfun->machine->highest_saved_stack_register + 1);
-      return;
-
     case 'r':
       /* Store the register to output a constant to.  */
       if (! REG_P (x))
@@ -1830,7 +1827,10 @@ mmix_print_operand_punct_valid_p (unsigned char code)
   /* A '+' is used for branch prediction, similar to other ports.  */
   return code == '+'
     /* A '.' is used for the %d in the POP %d,0 return insn.  */
-    || code == '.';
+    || code == '.'
+    /* A '!' is used for the number of saved registers, like when outputting
+       PUSHJ and PUSHGO. */
+    || code == '!';
 }
 
 /* TARGET_PRINT_OPERAND_ADDRESS.  */
diff --git a/gcc/config/mmix/mmix.md b/gcc/config/mmix/mmix.md
index 33e9c60982d..99be8263a1a 100644
--- a/gcc/config/mmix/mmix.md
+++ b/gcc/config/mmix/mmix.md
@@ -974,11 +974,9 @@ DIVU %1,%1,%2\;GET %0,:rR\;NEGU %2,0,%0\;CSNN %0,$255,%2")
   "%+B%D1 %2,%0")
 \f
 (define_expand "call"
-  [(parallel [(call (match_operand:QI 0 "memory_operand" "")
-		    (match_operand 1 "general_operand" ""))
-	      (use (match_operand 2 "general_operand" ""))
-	      (clobber (match_dup 4))])
-   (set (match_dup 4) (match_dup 3))]
+  [(parallel [(call (match_operand:QI 0 "memory_operand" "") (const_int 0))
+	      (clobber (match_dup 1))])
+   (set (match_dup 1) (match_dup 2))]
   ""
   "
 {
@@ -992,28 +990,24 @@ DIVU %1,%1,%2\;GET %0,:rR\;NEGU %2,0,%0\;CSNN %0,$255,%2")
       = replace_equiv_address (operands[0],
 			       force_reg (Pmode, XEXP (operands[0], 0)));
 
+  /* Note that we overwrite the generic operands[1] and operands[2]; we
+     don't use those values.  */
+  operands[1] = gen_rtx_REG (DImode, MMIX_INCOMING_RETURN_ADDRESS_REGNUM);
+
   /* Since the epilogue 'uses' the return address, and it is clobbered
      in the call, and we set it back after every call (all but one setting
      will be optimized away), integrity is maintained.  */
-  operands[3]
+  operands[2]
     = mmix_get_hard_reg_initial_val (Pmode,
 				     MMIX_INCOMING_RETURN_ADDRESS_REGNUM);
-
-  /* NULL gets passed as operand[2] when we get out of registers,
-     which later confuses gcc.  Replace it with const_int 0.  */
-  if (operands[2] == NULL_RTX)
-    operands[2] = const0_rtx;
-
-  operands[4] = gen_rtx_REG (DImode, MMIX_INCOMING_RETURN_ADDRESS_REGNUM);
 }")
 
 (define_expand "call_value"
   [(parallel [(set (match_operand 0 "" "")
 		   (call (match_operand:QI 1 "memory_operand" "")
-			 (match_operand 2 "general_operand" "")))
-	      (use (match_operand 3 "general_operand" ""))
-	      (clobber (match_dup 5))])
-   (set (match_dup 5) (match_dup 4))]
+			 (const_int 0)))
+	      (clobber (match_dup 2))])
+   (set (match_dup 2) (match_dup 3))]
   ""
   "
 {
@@ -1027,18 +1021,16 @@ DIVU %1,%1,%2\;GET %0,:rR\;NEGU %2,0,%0\;CSNN %0,$255,%2")
       = replace_equiv_address (operands[1],
 			       force_reg (Pmode, XEXP (operands[1], 0)));
 
+  /* Note that we overwrite the generic operands[2] and operands[3]; we
+     don't use those values.  */
+  operands[2] = gen_rtx_REG (DImode, MMIX_INCOMING_RETURN_ADDRESS_REGNUM);
+
   /* Since the epilogue 'uses' the return address, and it is clobbered
      in the call, and we set it back after every call (all but one setting
      will be optimized away), integrity is maintained.  */
-  operands[4]
+  operands[3]
     = mmix_get_hard_reg_initial_val (Pmode,
 				     MMIX_INCOMING_RETURN_ADDRESS_REGNUM);
-
-  /* See 'call'.  */
-  if (operands[3] == NULL_RTX)
-    operands[3] = const0_rtx;
-
-  operands[5] = gen_rtx_REG (DImode, MMIX_INCOMING_RETURN_ADDRESS_REGNUM);
 }")
 
 ;; Don't use 'p' here.  A 'p' must stand first in constraints, or reload
@@ -1059,25 +1051,23 @@ DIVU %1,%1,%2\;GET %0,:rR\;NEGU %2,0,%0\;CSNN %0,$255,%2")
 (define_insn "*call_real"
   [(call (mem:QI
 	  (match_operand:DI 0 "mmix_symbolic_or_address_operand" "s,rU"))
-	 (match_operand 1 "" ""))
-   (use (match_operand 2 "" ""))
+	 (const_int 0))
    (clobber (reg:DI MMIX_rJ_REGNUM))]
   ""
   "@
-   PUSHJ $%p2,%0
-   PUSHGO $%p2,%a0")
+   PUSHJ $%!,%0
+   PUSHGO $%!,%a0")
 
 (define_insn "*call_value_real"
   [(set (match_operand 0 "register_operand" "=r,r")
 	(call (mem:QI
 	       (match_operand:DI 1 "mmix_symbolic_or_address_operand" "s,rU"))
-	      (match_operand 2 "" "")))
-  (use (match_operand 3 "" ""))
-  (clobber (reg:DI MMIX_rJ_REGNUM))]
+	      (const_int 0)))
+   (clobber (reg:DI MMIX_rJ_REGNUM))]
   ""
   "@
-   PUSHJ $%p3,%1
-   PUSHGO $%p3,%a1")
+   PUSHJ $%!,%1
+   PUSHGO $%!,%a1")
 
 ;; I hope untyped_call and untyped_return are not needed for MMIX.
 ;; Users of Objective-C will notice.