Re: [PR64164] drop copyrename, integrate into expand

[Alexandre Oliva <aoliva@redhat.com>]

On Aug 16, 2015, Andreas Schwab <schwab@linux-m68k.org> wrote:

> On m68k:
> FAIL: gcc.c-torture/execute/20050316-1.c   -O0  execution test
> FAIL: gcc.c-torture/execute/20050316-2.c   -O0  execution test
> FAIL: gcc.c-torture/execute/20050316-3.c   -O0  execution test
> FAIL: gcc.c-torture/execute/simd-4.c   -O0  execution test
> FAIL: gcc.c-torture/execute/simd-6.c   -O0  execution test
> FAIL: gcc.dg/compat/vector-1 c_compat_x_tst.o-c_compat_y_tst.o execute

Thanks.  Interesting.  This exposes a more general situation than the
one I covered with the byref params: the general case does not require
the params to be passed by reference, but rather that the params require
a stack address that, if determined by cfgexpand, will cause them to be
computed too late for assign_parms' use.  The following patch appears to
fix the problem, applying the same logic of limited coalescing and
deferred address assignment to all params that can't live in pseudos,
and extending assign_parms' remaining case of copying incoming params to
new stack slots to fill in the blank address with that of the
newly-allocated stack slot.

Would you be so kind as to give it a spin on a m68k native?  TIA,


diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 0bc20f6..56571ce 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -172,17 +172,23 @@ leader_merge (tree cur, tree next)
   return cur;
 }
 
-/* Return true if VAR is a PARM_DECL or a RESULT_DECL of type BLKmode.
+/* Return true if VAR is a PARM_DECL or a RESULT_DECL that ought to be
+   assigned to a stack slot.  We can't have expand_one_ssa_partition
+   choose their address: the pseudo holding the address would be set
+   up too late for assign_params to copy the parameter if needed.
+
    Such parameters are likely passed as a pointer to the value, rather
    than as a value, and so we must not coalesce them, nor allocate
    stack space for them before determining the calling conventions for
-   them.  For their SSA_NAMEs, expand_one_ssa_partition emits RTL as
-   MEMs with pc_rtx as the address, and then it replaces the pc_rtx
-   with NULL so as to make sure the MEM is not used before it is
-   adjusted in assign_parm_setup_reg.  */
+   them.
+
+   For their SSA_NAMEs, expand_one_ssa_partition emits RTL as MEMs
+   with pc_rtx as the address, and then it replaces the pc_rtx with
+   NULL so as to make sure the MEM is not used before it is adjusted
+   in assign_parm_setup_reg.  */
 
 bool
-parm_maybe_byref_p (tree var)
+parm_in_stack_slot_p (tree var)
 {
   if (!var || VAR_P (var))
     return false;
@@ -190,7 +196,7 @@ parm_maybe_byref_p (tree var)
   gcc_assert (TREE_CODE (var) == PARM_DECL
 	      || TREE_CODE (var) == RESULT_DECL);
 
-  return TYPE_MODE (TREE_TYPE (var)) == BLKmode;
+  return !use_register_for_decl (var);
 }
 
 /* Return the partition of the default SSA_DEF for decl VAR.  */
@@ -1343,13 +1349,15 @@ expand_one_ssa_partition (tree var)
 
   if (!use_register_for_decl (var))
     {
-      if (parm_maybe_byref_p (SSA_NAME_VAR (var))
+      /* We can't risk having the parm assigned to a MEM location
+	 whose address references a pseudo, for the pseudo will only
+	 be set up after arguments are copied to the stack slot.  */
+      if (parm_in_stack_slot_p (SSA_NAME_VAR (var))
 	  && ssa_default_def_partition (SSA_NAME_VAR (var)) == part)
 	{
 	  expand_one_stack_var_at (var, pc_rtx, 0, 0);
 	  rtx x = SA.partition_to_pseudo[part];
 	  gcc_assert (GET_CODE (x) == MEM);
-	  gcc_assert (GET_MODE (x) == BLKmode);
 	  gcc_assert (XEXP (x, 0) == pc_rtx);
 	  /* Reset the address, so that any attempt to use it will
 	     ICE.  It will be adjusted in assign_parm_setup_reg.  */
diff --git a/gcc/cfgexpand.h b/gcc/cfgexpand.h
index 987cf356..d168672 100644
--- a/gcc/cfgexpand.h
+++ b/gcc/cfgexpand.h
@@ -22,7 +22,7 @@ along with GCC; see the file COPYING3.  If not see
 
 extern tree gimple_assign_rhs_to_tree (gimple);
 extern HOST_WIDE_INT estimated_stack_frame_size (struct cgraph_node *);
-extern bool parm_maybe_byref_p (tree);
+extern bool parm_in_stack_slot_p (tree);
 extern rtx get_rtl_for_parm_ssa_default_def (tree var);
 
 
diff --git a/gcc/function.c b/gcc/function.c
index 715c19f..eccd8c6 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -2934,6 +2934,16 @@ assign_parm_setup_block_p (struct assign_parm_data_one *data)
   return false;
 }
 
+static bool
+parm_in_unassigned_mem_p (tree decl, rtx from_expand)
+{
+  bool result = MEM_P (from_expand) && !XEXP (from_expand, 0);
+
+  gcc_assert (result == parm_in_stack_slot_p (decl));
+
+  return result;
+}
+
 /* A subroutine of assign_parms.  Arrange for the parameter to be
    present and valid in DATA->STACK_RTL.  */
 
@@ -2956,8 +2966,7 @@ assign_parm_setup_block (struct assign_parm_data_all *all,
     {
       DECL_ALIGN (parm) = MAX (DECL_ALIGN (parm), BITS_PER_WORD);
       rtx from_expand = rtl_for_parm (all, parm);
-      if (from_expand && (!parm_maybe_byref_p (parm)
-			  || XEXP (from_expand, 0) != NULL_RTX))
+      if (from_expand && !parm_in_unassigned_mem_p (parm, from_expand))
 	stack_parm = copy_rtx (from_expand);
       else
 	{
@@ -2968,8 +2977,7 @@ assign_parm_setup_block (struct assign_parm_data_all *all,
 	  if (from_expand)
 	    {
 	      gcc_assert (GET_CODE (stack_parm) == MEM);
-	      gcc_assert (GET_CODE (from_expand) == MEM);
-	      gcc_assert (XEXP (from_expand, 0) == NULL_RTX);
+	      gcc_assert (parm_in_unassigned_mem_p (parm, from_expand));
 	      XEXP (from_expand, 0) = XEXP (stack_parm, 0);
 	      PUT_MODE (from_expand, GET_MODE (stack_parm));
 	      stack_parm = copy_rtx (from_expand);
@@ -3121,7 +3129,7 @@ assign_parm_setup_reg (struct assign_parm_data_all *all, tree parm,
       if (GET_MODE (parmreg) != promoted_nominal_mode)
 	parmreg = gen_lowpart (promoted_nominal_mode, parmreg);
     }
-  else if (!from_expand || parm_maybe_byref_p (parm))
+  else if (!from_expand || parm_in_unassigned_mem_p (parm, from_expand))
     {
       parmreg = gen_reg_rtx (promoted_nominal_mode);
       if (!DECL_ARTIFICIAL (parm))
@@ -3349,7 +3357,7 @@ assign_parm_setup_reg (struct assign_parm_data_all *all, tree parm,
 	  did_conversion = true;
 	}
       else if (GET_MODE (parmreg) == BLKmode)
-	gcc_assert (parm_maybe_byref_p (parm));
+	gcc_assert (parm_in_stack_slot_p (parm));
       else
 	emit_move_insn (parmreg, src);
 
@@ -3455,12 +3463,15 @@ assign_parm_setup_stack (struct assign_parm_data_all *all, tree parm,
   if (data->entry_parm != data->stack_parm)
     {
       rtx src, dest;
+      rtx from_expand = NULL_RTX;
 
       if (data->stack_parm == 0)
 	{
-	  rtx x = data->stack_parm = rtl_for_parm (all, parm);
-	  if (x)
-	    gcc_assert (GET_MODE (x) == GET_MODE (data->entry_parm));
+	  from_expand = rtl_for_parm (all, parm);
+	  if (from_expand)
+	    gcc_assert (GET_MODE (from_expand) == GET_MODE (data->entry_parm));
+	  else if (!parm_in_unassigned_mem_p (parm, from_expand))
+	    data->stack_parm = from_expand;
 	}
 
       if (data->stack_parm == 0)
@@ -3472,7 +3483,16 @@ assign_parm_setup_stack (struct assign_parm_data_all *all, tree parm,
 	    = assign_stack_local (GET_MODE (data->entry_parm),
 				  GET_MODE_SIZE (GET_MODE (data->entry_parm)),
 				  align);
-	  set_mem_attributes (data->stack_parm, parm, 1);
+	  if (!from_expand)
+	    set_mem_attributes (data->stack_parm, parm, 1);
+	  else
+	    {
+	      gcc_assert (GET_CODE (data->stack_parm) == MEM);
+	      gcc_assert (parm_in_unassigned_mem_p (parm, from_expand));
+	      XEXP (from_expand, 0) = XEXP (data->stack_parm, 0);
+	      PUT_MODE (from_expand, GET_MODE (data->stack_parm));
+	      data->stack_parm = copy_rtx (from_expand);
+	    }
 	}
 
       dest = validize_mem (copy_rtx (data->stack_parm));
diff --git a/gcc/tree-ssa-coalesce.c b/gcc/tree-ssa-coalesce.c
index 08ce72c..6468012 100644
--- a/gcc/tree-ssa-coalesce.c
+++ b/gcc/tree-ssa-coalesce.c
@@ -1386,8 +1386,8 @@ gimple_can_coalesce_p (tree name1, tree name2)
 	 because it may be passed by reference.  */
       return ((!var1 || VAR_P (var1)) && (!var2 || VAR_P (var2)))
 	|| (/* The case var1 == var2 is already covered above.  */
-	    !parm_maybe_byref_p (var1)
-	    && !parm_maybe_byref_p (var2)
+	    !parm_in_stack_slot_p (var1)
+	    && !parm_in_stack_slot_p (var2)
 	    && promote_ssa_mode (name1, NULL) == promote_ssa_mode (name2, NULL));
     }
 


-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer