Patch to document STACK_PUSH_CODE, deal with it, and other things.

[Geoffrey Keating <geoffk at thief dot cygnus dot com>]

This deals with two issues in emit_move_insn_1 in the same (rarely
used) chunk of code.  The code operates only when a push insn is
generated but there is no mov* expander for the appropriate mode,
and it was wrong in a number of ways.

I'm also taking this opportunity to commit Toshi's patch.

Bootstrapped and tested on x86-linux, and also tested on the internal
Red Hat tree with a currently-confidential port.

-- 
Geoff Keating <geoffk@redhat.com>

===File ~/patches/gcc-stackpushcode.patch===================
2001-07-02  Geoffrey Keating  <geoffk@redhat.com>

	* doc/tm.texi (Frame Layout): Document STACK_PUSH_CODE.

	* expr.c (emit_move_insn_1): Deal with non-default
	STACK_PUSH_CODE.

	* expr.c (emit_single_push_insn): Fix warning.

2001-07-02  Toshiyasu Morita  <toshiyasu.morita@hsa.hitachi.com>

	* expr.c (emit_move_insn_1): Avoid modifying
	cfun->expr->x_stack_pointer when PUSH_ROUNDING is defined.

Index: expr.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/expr.c,v
retrieving revision 1.331
diff -p -u -p -r1.331 expr.c
--- expr.c	2001/07/01 20:49:58	1.331
+++ expr.c	2001/07/02 19:56:54
@@ -2973,8 +2973,39 @@ emit_move_insn_1 (x, y)
 	 X with a reference to the stack pointer.  */
       if (push_operand (x, GET_MODE (x)))
 	{
-	  anti_adjust_stack (GEN_INT (GET_MODE_SIZE (GET_MODE (x))));
-	  x = change_address (x, VOIDmode, stack_pointer_rtx);
+	  rtx temp;
+	  enum rtx_code code;
+	  
+	  /* Do not use anti_adjust_stack, since we don't want to update
+	     stack_pointer_delta.  */
+	  temp = expand_binop (Pmode,
+#ifdef STACK_GROWS_DOWNWARD
+			       sub_optab,
+#else
+			       add_optab,
+#endif
+			       stack_pointer_rtx,
+			       GEN_INT
+				 (PUSH_ROUNDING (GET_MODE_SIZE (GET_MODE (x)))),
+			       stack_pointer_rtx,
+			       0,
+			       OPTAB_LIB_WIDEN);
+          if (temp != stack_pointer_rtx)
+            emit_move_insn (stack_pointer_rtx, temp);
+
+	  code = GET_CODE (XEXP (x, 0));
+	  /* Just hope that small offsets off SP are OK.  */
+	  if (code == POST_INC)
+	    temp = gen_rtx_PLUS (Pmode, stack_pointer_rtx, 
+				GEN_INT (-(HOST_WIDE_INT)
+					   GET_MODE_SIZE (GET_MODE (x))));
+	  else if (code == POST_DEC)
+	    temp = gen_rtx_PLUS (Pmode, stack_pointer_rtx, 
+				GEN_INT (GET_MODE_SIZE (GET_MODE (x))));
+	  else
+	    temp = stack_pointer_rtx;
+
+	  x = change_address (x, VOIDmode, temp);
 	}
 #endif
 
@@ -3142,7 +3173,7 @@ emit_single_push_insn (mode, x, type)
 {
 #ifdef PUSH_ROUNDING
   rtx dest_addr;
-  int rounded_size = PUSH_ROUNDING (GET_MODE_SIZE (mode));
+  unsigned rounded_size = PUSH_ROUNDING (GET_MODE_SIZE (mode));
   rtx dest;
 
   if (GET_MODE_SIZE (mode) == rounded_size)
@@ -3151,7 +3182,7 @@ emit_single_push_insn (mode, x, type)
     {
 #ifdef STACK_GROWS_DOWNWARD
       dest_addr = gen_rtx_PLUS (Pmode, stack_pointer_rtx,
-				GEN_INT (-rounded_size));
+				GEN_INT (-(HOST_WIDE_INT)rounded_size));
 #else
       dest_addr = gen_rtx_PLUS (Pmode, stack_pointer_rtx,
 				GEN_INT (rounded_size));
Index: doc/tm.texi
===================================================================
RCS file: /cvs/gcc/gcc/gcc/doc/tm.texi,v
retrieving revision 1.20
diff -p -u -p -r1.20 tm.texi
--- tm.texi	2001/07/01 23:21:11	1.20
+++ tm.texi	2001/07/02 19:56:56
@@ -2507,6 +2507,23 @@ When we say, ``define this macro if @dot
 compiler checks this macro only with @code{#ifdef} so the precise
 definition used does not matter.
 
+@findex STACK_PUSH_CODE
+@item STACK_PUSH_CODE
+
+This macro defines the operation used when something is pushed
+on the stack.  In RTL, a push operation will be
+@code{(set (mem (STACK_PUSH_CODE (reg sp))) ...)}
+
+The choices are @code{PRE_DEC}, @code{POST_DEC}, @code{PRE_INC},
+and @code{POST_INC}.  Which of these is correct depends on
+the stack direction and on whether the stack pointer points
+to the last item on the stack or whether it points to the
+space for the next item on the stack.
+
+The default is @code{PRE_DEC} when @code{STACK_GROWS_DOWNWARD} is
+defined, which is almost always right, and @code{PRE_INC} otherwise,
+which is often wrong.
+
 @findex FRAME_GROWS_DOWNWARD
 @item FRAME_GROWS_DOWNWARD
 Define this macro if the addresses of local variable slots are at negative
============================================================