[PATCH/m68k] fix jump table addressing

Roman Zippel zippel@linux-m68k.org
Wed Sep 19 14:01:00 GMT 2007


Hi,

This removes the workaround for some assemblers to address the jump
table with "Lnnn-LInnn-2.b(%pc)" and simply uses "Lnnn(%pc)" now, this
means the code to generate the extra label can go now.
As a side effect it allows gas to generate the best addressing based on
the offset.

The patch had been previously approved here
http://gcc.gnu.org/ml/gcc-patches/2007-02/msg00407.html
but there were conflicts with the ColdFire patches, so this patch is now 
updated and retested.

bye, Roman

200x-xx-xx  Roman Zippel <zippel@linux-m68k.org>

	* config/m68k/m68k.c (output_move_himode): Remove jump table
	recognition.
	config/m68k/m68k.md (lea): Likewise.
	* config/m68k/m68k.c (print_operand_address): Use simple pc
	relative addressing.

---

 gcc/config/m68k/m68k.c  |   33 ++-------------------------------
 gcc/config/m68k/m68k.md |   23 ++---------------------
 2 files changed, 4 insertions(+), 52 deletions(-)

Index: gcc/gcc/config/m68k/m68k.c
===================================================================
--- gcc.orig/gcc/config/m68k/m68k.c
+++ gcc/gcc/config/m68k/m68k.c
@@ -2362,25 +2362,6 @@ output_move_himode (rtx *operands)
     }
   else if (CONSTANT_P (operands[1]))
     return "move%.l %1,%0";
-  /* Recognize the insn before a tablejump, one that refers
-     to a table of offsets.  Such an insn will need to refer
-     to a label on the insn.  So output one.  Use the label-number
-     of the table of offsets to generate this label.  This code,
-     and similar code below, assumes that there will be at most one
-     reference to each table.  */
-  if (GET_CODE (operands[1]) == MEM
-      && GET_CODE (XEXP (operands[1], 0)) == PLUS
-      && GET_CODE (XEXP (XEXP (operands[1], 0), 1)) == LABEL_REF
-      && GET_CODE (XEXP (XEXP (operands[1], 0), 0)) != PLUS)
-    {
-      rtx labelref = XEXP (XEXP (operands[1], 0), 1);
-      if (MOTOROLA)
-	asm_fprintf (asm_out_file, "\t.set %LLI%d,.+2\n",
-		     CODE_LABEL_NUMBER (XEXP (labelref, 0)));
-      else
-	(*targetm.asm_out.internal_label) (asm_out_file, "LI",
-					   CODE_LABEL_NUMBER (XEXP (labelref, 0)));
-    }
   return "move%.w %1,%0";
 }
 
@@ -3822,16 +3803,6 @@ print_operand (FILE *file, rtx op, int l
    It is possible for PIC to generate a (plus (label_ref...) (reg...))
    and we handle that just like we would a (plus (symbol_ref...) (reg...)).
 
-   Some SGS assemblers have a bug such that "Lnnn-LInnn-2.b(pc,d0.l*2)"
-   fails to assemble.  Luckily "Lnnn(pc,d0.l*2)" produces the results
-   we want.  This difference can be accommodated by using an assembler
-   define such "LDnnn" to be either "Lnnn-LInnn-2.b", "Lnnn", or any other
-   string, as necessary.  This is accomplished via the ASM_OUTPUT_CASE_END
-   macro.  See m68k/sgs.h for an example; for versions without the bug.
-   Some assemblers refuse all the above solutions.  The workaround is to
-   emit "K(pc,d0.l*2)" with K being a small constant known to give the
-   right behavior.
-
    They also do not like things like "pea 1.w", so we simple leave off
    the .w on small constants. 
 
@@ -3905,7 +3876,7 @@ print_operand_address (FILE *file, rtx a
 	{
 	  /* Print the "offset(base" component.  */
 	  if (labelno >= 0)
-	    asm_fprintf (file, "%LL%d-%LLI%d.b(%Rpc,", labelno, labelno);
+	    asm_fprintf (file, "%LL%d(%Rpc,", labelno);
 	  else
 	    {
 	      if (address.offset)
@@ -3943,7 +3914,7 @@ print_operand_address (FILE *file, rtx a
 	    {
 	      /* Print the "base@(offset" component.  */
 	      if (labelno >= 0)
-		asm_fprintf (file, "%Rpc@(%LL%d-%LLI%d-2:b", labelno, labelno);
+		asm_fprintf (file, "%Rpc@(%LL%d", labelno);
 	      else
 		{
 		  if (address.base)
Index: gcc/gcc/config/m68k/m68k.md
===================================================================
--- gcc.orig/gcc/config/m68k/m68k.md
+++ gcc/gcc/config/m68k/m68k.md
@@ -7297,30 +7297,11 @@
 
 ;; This should not be used unless the add/sub insns can't be.
 
-(define_insn ""
+(define_insn "*lea"
   [(set (match_operand:SI 0 "nonimmediate_operand" "=a")
 	(match_operand:QI 1 "address_operand" "p"))]
   ""
-{
-  /* Recognize an insn that refers to a table of offsets.  Such an insn will
-     need to refer to a label on the insn.  So output one.  Use the
-     label-number of the table of offsets to generate this label.  This code,
-     and similar code above, assumes that there will be at most one reference
-     to each table.  */
-  if (GET_CODE (operands[1]) == PLUS
-      && GET_CODE (XEXP (operands[1], 1)) == LABEL_REF
-      && GET_CODE (XEXP (operands[1], 0)) != PLUS)
-    {
-      rtx labelref = XEXP (operands[1], 1);
-      if (MOTOROLA)
-        asm_fprintf (asm_out_file, "\\t.set %LLI%d,.+2\\n",
-		     CODE_LABEL_NUMBER (XEXP (labelref, 0)));
-      else
-        (*targetm.asm_out.internal_label) (asm_out_file, "LI",
-		     CODE_LABEL_NUMBER (XEXP (labelref, 0)));
-    }
-  return "lea %a1,%0";
-})
+  "lea %a1,%0")
 
 ;; This is the first machine-dependent peephole optimization.
 ;; It is useful when a floating value is returned from a function call



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