200x-xx-xx Kazu Hirata <kazu@codesourcery.com> Richard Sandiford <richard@codesourcery.com>

gcc/
200x-xx-xx  Kazu Hirata  <kazu@codesourcery.com>
	    Richard Sandiford  <richard@codesourcery.com>

	* doc/tm.texi (TARGET_FUNCTION_VALUE): Expand documentation of
	parallels.
	* calls.c (expand_call): If the return value is a PARALLEL,
	extract its first member.
	* config/m68k/linux.h (FUNCTION_EXTRA_EPILOGUE): Remove.
	* config/m68k/m68k.c (m68k_output_function_epilogue): Don't
	use FUNCTION_EXTRA_EPILOGUE.
	(m68k_function_value): Return a PARALLEL if the return value
	is of a pointer type.
	* config/m68k/netbsd-elf.h (current_function_returns_pointer)
	(FUNCTION_EXTRA_EPILOGUE): Remove.
	* config/m68k/m68k.md (D0_REG): New constant.

Co-Authored-By: Richard Sandiford <richard@codesourcery.com>

From-SVN: r120929

7 files changed, 58 insertions, 42 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 102078d..f433dc5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,4 +1,20 @@
 2007-01-18  Kazu Hirata  <kazu@codesourcery.com>
+	    Richard Sandiford  <richard@codesourcery.com>
+
+	* doc/tm.texi (TARGET_FUNCTION_VALUE): Expand documentation of
+	parallels.
+	* calls.c (expand_call): If the return value is a PARALLEL,
+	extract its first member.
+	* config/m68k/linux.h (FUNCTION_EXTRA_EPILOGUE): Remove.
+	* config/m68k/m68k.c (m68k_output_function_epilogue): Don't
+	use FUNCTION_EXTRA_EPILOGUE.
+	(m68k_function_value): Return a PARALLEL if the return value
+	is of a pointer type.
+	* config/m68k/netbsd-elf.h (current_function_returns_pointer)
+	(FUNCTION_EXTRA_EPILOGUE): Remove.
+	* config/m68k/m68k.md (D0_REG): New constant.
+
+2007-01-18  Kazu Hirata  <kazu@codesourcery.com>
 
 	* config/m68k/m68k.c (m68k_output_function_epilogue): Don't
 	output a NOP for empty epilogues.
diff --git a/gcc/calls.c b/gcc/calls.c
index c0d1f8c..0ca03f8 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -2566,6 +2566,19 @@ expand_call (tree exp, rtx target, int ignore)
 	  else
 	    valreg = hard_function_value (TREE_TYPE (exp), fndecl, fntype,
 					  (pass == 0));
+
+	  /* If VALREG is a PARALLEL whose first member has a zero
+	     offset, use that.  This is for targets such as m68k that
+	     return the same value in multiple places.  */
+	  if (GET_CODE (valreg) == PARALLEL)
+	    {
+	      rtx elem = XVECEXP (valreg, 0, 0);
+	      rtx where = XEXP (elem, 0);
+	      rtx offset = XEXP (elem, 1);
+	      if (offset == const0_rtx
+		  && GET_MODE (where) == GET_MODE (valreg))
+		valreg = where;
+	    }
 	}
 
       /* Precompute all register parameters.  It isn't safe to compute anything
diff --git a/gcc/config/m68k/linux.h b/gcc/config/m68k/linux.h
index cdb8817..2c72d49 100644
--- a/gcc/config/m68k/linux.h
+++ b/gcc/config/m68k/linux.h
@@ -179,20 +179,6 @@ Boston, MA 02110-1301, USA.  */
 #define FUNCTION_VALUE(VALTYPE, FUNC)					\
   m68k_function_value (VALTYPE, FUNC)
 
-/* For compatibility with the large body of existing code which does
-   not always properly declare external functions returning pointer
-   types, the m68k/SVR4 convention is to copy the value returned for
-   pointer functions from a0 to d0 in the function epilogue, so that
-   callers that have neglected to properly declare the callee can
-   still find the correct return value.  */
-
-#define FUNCTION_EXTRA_EPILOGUE(FILE, SIZE)				\
-do {									\
-  if (current_function_returns_pointer					\
-      && ! find_equiv_reg (0, get_last_insn (), 0, 0, 0, 8, Pmode))	\
-    asm_fprintf (FILE, "\tmove.l %Ra0,%Rd0\n");				\
-} while (0);
-
 /* Define how to find the value returned by a library function
    assuming the value has mode MODE.
    For m68k/SVR4 look for integer values in d0, pointer values in d0
diff --git a/gcc/config/m68k/m68k.c b/gcc/config/m68k/m68k.c
index 41f61c7..81dded1 100644
--- a/gcc/config/m68k/m68k.c
+++ b/gcc/config/m68k/m68k.c
@@ -1057,10 +1057,6 @@ m68k_output_function_epilogue (FILE *stream,
   if (insn && GET_CODE (insn) == BARRIER)
     return;
 
-#ifdef FUNCTION_EXTRA_EPILOGUE
-  FUNCTION_EXTRA_EPILOGUE (stream, size);
-#endif
-
   fsize = current_frame.size;
 
   /* FIXME: leaf_function_p below is too strong.
@@ -3894,9 +3890,26 @@ m68k_function_value (tree valtype, tree func ATTRIBUTE_UNUSED)
     break;
   }
 
-  /* If the function returns a pointer, push that into %a0 */
-  if (POINTER_TYPE_P (valtype))
-    return gen_rtx_REG (mode, 8);
+  /* If the function returns a pointer, push that into %a0.  */
+  if (func && POINTER_TYPE_P (TREE_TYPE (TREE_TYPE (func))))
+    /* For compatibility with the large body of existing code which
+       does not always properly declare external functions returning
+       pointer types, the m68k/SVR4 convention is to copy the value
+       returned for pointer functions from a0 to d0 in the function
+       epilogue, so that callers that have neglected to properly
+       declare the callee can still find the correct return value in
+       d0.  */
+    return gen_rtx_PARALLEL
+      (mode,
+       gen_rtvec (2,
+		  gen_rtx_EXPR_LIST (VOIDmode,
+				     gen_rtx_REG (mode, A0_REG),
+				     const0_rtx),
+		  gen_rtx_EXPR_LIST (VOIDmode,
+				     gen_rtx_REG (mode, D0_REG),
+				     const0_rtx)));
+  else if (POINTER_TYPE_P (valtype))
+    return gen_rtx_REG (mode, A0_REG);
   else
-    return gen_rtx_REG (mode, 0);
+    return gen_rtx_REG (mode, D0_REG);
 }
diff --git a/gcc/config/m68k/m68k.md b/gcc/config/m68k/m68k.md
index b14b3c9..8481fcd 100644
--- a/gcc/config/m68k/m68k.md
+++ b/gcc/config/m68k/m68k.md
@@ -124,7 +124,8 @@
 
 ;; Registers by name.
 (define_constants
-  [(A0_REG		8)
+  [(D0_REG		0)
+   (A0_REG		8)
    (SP_REG		15)
   ])
 
diff --git a/gcc/config/m68k/netbsd-elf.h b/gcc/config/m68k/netbsd-elf.h
index 234d017..c67f6f8 100644
--- a/gcc/config/m68k/netbsd-elf.h
+++ b/gcc/config/m68k/netbsd-elf.h
@@ -273,24 +273,6 @@ while (0)
   m68k_function_value (VALTYPE, FUNC)
 
 
-/* For compatibility with the large body of existing code which does
-   not always properly declare external functions returning pointer
-   types, the m68k/SVR4 convention is to copy the value returned for
-   pointer functions from a0 to d0 in the function epilogue, so that
-   callers that have neglected to properly declare the callee can
-   still find the correct return value.  */
-
-extern int current_function_returns_pointer;
-#define FUNCTION_EXTRA_EPILOGUE(FILE, SIZE) 				\
-do									\
-  {									\
-    if (current_function_returns_pointer				\
-	&& ! find_equiv_reg (0, get_last_insn (), 0, 0, 0, 8, Pmode))	\
-      asm_fprintf (FILE, "\tmove.l %Ra0,%Rd0\n");			\
-  }									\
-while (0)
-
-
 /* Define how to find the value returned by a library function
    assuming the value has mode MODE.
    For m68k/SVR4 look for integer values in d0, pointer values in d0
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index dcf7e02..ad70779 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -4107,7 +4107,12 @@ place regardless of mode.)  The value of the expression is usually a
 @code{reg} RTX for the hard register where the return value is stored.
 The value can also be a @code{parallel} RTX, if the return value is in
 multiple places.  See @code{FUNCTION_ARG} for an explanation of the
-@code{parallel} form.
+@code{parallel} form.   Note that the callee will populate every
+location specified in the @code{parallel}, but if the first element of
+the @code{parallel} contains the whole return value, callers will use
+that element as the canonical location and ignore the others.  The m68k
+port uses this type of @code{parallel} to return pointers in both
+@samp{%a0} (the canonical location) and @samp{%d0}.
 
 If @code{TARGET_PROMOTE_FUNCTION_RETURN} returns true, you must apply
 the same promotion rules specified in @code{PROMOTE_MODE} if