Re: [PATCH, m68k] Fix PR target/41302

[Maxim Kuvyrkov <maxim at codesourcery dot com>]

Maxim Kuvyrkov wrote:
> Jeff Law wrote:
> > On 10/30/09 04:14, Maxim Kuvyrkov wrote:
> > > The attached patch fixes <gcc.gnu.org/PR41302>.
> > >
> > > As described in the PR, the problem is in m68k_ok_for_sibcall_p() 
> > > allowing sibcalls of functions that return the result in a different 
> > > location (register A0) from what the current function expects 
> > > (register D0).
> > >
> > > This patch ports similar code from the arm backend, and also handles 
> > > a specific to m68k case when the result is returned in both D0 and A0 
> > > registers.
> > >
> > > Tested on coldfire-elf with no regressions on gcc, g++ and libstdc++ 
> > > testsuites.  OK for trunk?
> > >
> > > Thanks,
> > The way you've written the condition below is somewhat odd and it's 
> > bloody hard to see the empty statement semi-colon in the if-clause.
>
> Noted.
...
> While making the changes I've spotted a couple of quirks in the patch, 
> and now I'm testing an updated version.  Will follow up once the tests 
> are finished.

Here is an updated version.  Turned out that testing on coldfire-elf was 
of little relevance as ABI of cf-elf is different from cf-linux (cf-elf 
always returns result in D0).  So I've fixed the patch to handle 
different ABIs correctly and updated the testcase.

Tested on coldfire-linux, ok to check in?

--
Maxim Kuvyrkov
CodeSourcery
maxim@codesourcery.com
(650) 331-3385 x724

2009-11-03  Maxim Kuvyrkov  <maxim@codesourcery.com>

	PR target/41302
	* config/m68k/m68k.c (m68k_reg_present_p): New static function.
	(m68k_ok_for_sibcall_p): Handle different result return locations.

2009-11-03  Maxim Kuvyrkov  <maxim@codesourcery.com>

	PR target/41302
	* gcc.target/m68k/pr41302.c: New test.

Index: testsuite/gcc.target/m68k/pr41302.c
===================================================================
--- testsuite/gcc.target/m68k/pr41302.c	(revision 0)
+++ testsuite/gcc.target/m68k/pr41302.c	(revision 0)
@@ -0,0 +1,28 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler "move.l \%d0,\%a0" { target *linux* } } } */
+
+struct pts {
+  int c;
+};
+
+unsigned int bar (struct pts *a, int b);
+
+struct pts * foo (struct pts *a, int b)
+{
+  return (struct pts *) bar (a, b);
+}
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler "move.l \%d0,\%a0" { target *linux* } } } */
+
+struct pts {
+  int c;
+};
+
+unsigned int bar (struct pts *a, int b);
+
+struct pts * foo (struct pts *a, int b)
+{
+  return (struct pts *) bar (a, b);
+}
Index: config/m68k/m68k.c
===================================================================
--- config/m68k/m68k.c	(revision 153734)
+++ config/m68k/m68k.c	(working copy)
@@ -1399,6 +1399,30 @@ flags_in_68881 (void)
   return cc_status.flags & CC_IN_68881;
 }
 
+/* Return true if PARALLEL contains register REGNO.  */
+static bool
+m68k_reg_present_p (const_rtx parallel, unsigned int regno)
+{
+  int i;
+
+  if (REG_P (parallel) && REGNO (parallel) == regno)
+    return true;
+
+  if (GET_CODE (parallel) != PARALLEL)
+    return false;
+
+  for (i = 0; i < XVECLEN (parallel, 0); ++i)
+    {
+      const_rtx x;
+
+      x = XEXP (XVECEXP (parallel, 0, i), 0);
+      if (REG_P (x) && REGNO (x) == regno)
+	return true;
+    }
+
+  return false;
+}
+
 /* Implement TARGET_FUNCTION_OK_FOR_SIBCALL_P.  */
 
 static bool
@@ -1411,6 +1435,26 @@ m68k_ok_for_sibcall_p (tree decl, tree e
   if (CALL_EXPR_STATIC_CHAIN (exp))
     return false;
 
+  if (!VOID_TYPE_P (TREE_TYPE (DECL_RESULT (cfun->decl))))
+    {
+      /* Check that the return value locations are the same.  For
+	 example that we aren't returning a value from the sibling in
+	 a D0 register but then need to transfer it to a A0 register.  */
+      rtx cfun_value;
+      rtx call_value;
+
+      cfun_value = FUNCTION_VALUE (TREE_TYPE (DECL_RESULT (cfun->decl)),
+				   cfun->decl);
+      call_value = FUNCTION_VALUE (TREE_TYPE (exp), decl);
+
+      /* Check that the values are equal or that the result the callee
+	 function returns is superset of what the current function returns.  */
+      if (!(rtx_equal_p (cfun_value, call_value)
+	    || (REG_P (cfun_value)
+		&& m68k_reg_present_p (call_value, REGNO (cfun_value)))))
+	return false;
+    }
+
   kind = m68k_get_function_kind (current_function_decl);
   if (kind == m68k_fk_normal_function)
     /* We can always sibcall from a normal function, because it's
@@ -5188,6 +5232,9 @@ m68k_libcall_value (enum machine_mode mo
   return gen_rtx_REG (mode, m68k_libcall_value_in_a0_p ? A0_REG : D0_REG);
 }
 
+/* Location in which function value is returned.
+   NOTE: Due to differences in ABIs, don't call this function directly,
+   use FUNCTION_VALUE instead.  */
 rtx
 m68k_function_value (const_tree valtype, const_tree func ATTRIBUTE_UNUSED)
 {