Re: [PR64164] drop copyrename, integrate into expand

[Alexandre Oliva <aoliva@redhat.com>]

On Aug 18, 2015, Alexandre Oliva <aoliva@redhat.com> wrote:

>>> On Aug 17, 2015, Christophe Lyon <christophe.lyon@linaro.org> wrote:
>>>> Since this was committed (r226901), I can see that the compiler build
>>>> fails for armeb targets, when building libgcc:

> This patch fixes this particular case.  I'll also add this configuration
> to the cross build tests I'm going to rerun shortly, before submitting a
> followup formally, to see whether other non-MEM mems need to be handled
> explicitly.

On Aug 17, 2015, Andreas Schwab <schwab@linux-m68k.org> wrote:

> Andreas Schwab <schwab@linux-m68k.org> writes:

>> Alexandre Oliva <aoliva@redhat.com> writes:
>> 
>>> Would you be so kind as to give it a spin on a m68k native?  TIA,
>> 
>> I tried it on ia64, and it falls flat on the floor.

> It fixes the m68k failures, though.

On Aug 17, 2015, Alexandre Oliva <aoliva@redhat.com> wrote:

>> I tried it on ia64, and it falls flat on the floor.

> Doh, I see a logic flaw in the patch I posted.

There were other shortcomings in the snippets I posted before, revealed
by testing on on various other targets: remaining BLKmode asserts,
failure to deal with parms without a default def and split complex args
with an unassigned stack address.  This patch fixes them all.

It was regstrapped on x86_64-linux-gnu, i686-linux-gnu, ppc64-linux-gnu,
ppc64el-linux-gnu, and further tested with a compile-only 'make all' on
a binutils+gcc+newlib tree on all tens of cross targets mentioned
before, plus the armeb configuration Christophe mentioned.

Ok to install?


[PR64164] fix regressions reported on m68k and armeb

From: Alexandre Oliva <aoliva@redhat.com>

Defer stack slot address assignment for all parms that can't live in
pseudos, and accept pseudos assignments in assign_param_setup_block.

for  gcc/ChangeLog

	PR rtl-optimization/64164
	* cfgexpand.c (parm_maybe_byref_p): Renamed to...
	(parm_in_stack_slot_p): ... this.  Disregard mode, what
	matters is whether the parm will live in a pseudo or a stack
	slot.
	(expand_one_ssa_partition): Deal with params without a default
	def.  Disregard mode.
	* cfgexpand.h: Renamed function declaration.
	* tree-ssa-coalesce.c: Adjust.
	* function.c (split_complex_args): Allocate stack slot for
	unassigned parms before splitting.
	(parm_in_unassigned_mem_p): New.  Use it instead of
	parm_maybe_byref_p throughout this file.
	(assign_parm_setup_block): Use it.  Accept pseudos in the
	expand-assigned rtl.
	(assign_parm_setup_reg): Drop BLKmode requirement.
	(assign_parm_setup_stack): Allocate and fill in the address of
	unassigned MEM parms.
---
 gcc/cfgexpand.c         |   44 ++++++++++++++++++++++------
 gcc/cfgexpand.h         |    2 +
 gcc/function.c          |   74 ++++++++++++++++++++++++++++++++++++++++-------
 gcc/tree-ssa-coalesce.c |    4 +--
 4 files changed, 100 insertions(+), 24 deletions(-)

diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 0bc20f6..d567a87 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.  */
@@ -1343,17 +1349,35 @@ expand_one_ssa_partition (tree var)
 
   if (!use_register_for_decl (var))
     {
-      if (parm_maybe_byref_p (SSA_NAME_VAR (var))
-	  && ssa_default_def_partition (SSA_NAME_VAR (var)) == part)
+      /* 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 the parm doesn't have a default def (e.g., because its
+	 incoming value is unused), then we want to let assign_params
+	 do the allocation, too.  In this case we want to make sure
+	 SSA_NAMEs associated with the parm don't get assigned to more
+	 than one partition, lest we'd create two unassigned stac
+	 slots for the same parm, thus the assert at the end of the
+	 block.  */
+      if (parm_in_stack_slot_p (SSA_NAME_VAR (var))
+	  && (ssa_default_def_partition (SSA_NAME_VAR (var)) == part
+	      || !ssa_default_def (cfun, SSA_NAME_VAR (var))))
 	{
 	  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.  */
 	  XEXP (x, 0) = NULL_RTX;
+	  /* If the RTL associated with the parm is not what we have
+	     just created, the parm has been split over multiple
+	     partitions.  In order for this to work, we must have a
+	     default def for the parm, otherwise assign_params won't
+	     know what to do.  */
+	  gcc_assert (DECL_RTL_IF_SET (SSA_NAME_VAR (var)) == x
+		      || ssa_default_def (cfun, SSA_NAME_VAR (var)));
 	}
       else if (defer_stack_allocation (var, true))
 	add_stack_var (var);
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..222c76f 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -153,6 +153,7 @@ static void do_clobber_return_reg (rtx, void *);
 static void do_use_return_reg (rtx, void *);
 static rtx rtl_for_parm (struct assign_parm_data_all *, tree);
 static void maybe_reset_rtl_for_parm (tree);
+static bool parm_in_unassigned_mem_p (tree, rtx);
 
 \f
 /* Stack of nested functions.  */
@@ -2326,6 +2327,22 @@ split_complex_args (struct assign_parm_data_all *all, vec<tree> *args)
 	      rtx rtl = rtl_for_parm (all, cparm);
 	      if (rtl)
 		{
+		  /* If this is parm is unassigned, assign it now: the
+		     newly-created decls wouldn't expect the need for
+		     assignment, and if they were assigned
+		     independently, they might not end up in adjacent
+		     slots, so unsplit wouldn't be able to fill in the
+		     unassigned address of the complex MEM.  */
+		  if (parm_in_unassigned_mem_p (cparm, rtl))
+		    {
+		      int align = STACK_SLOT_ALIGNMENT
+			(TREE_TYPE (cparm), GET_MODE (rtl), MEM_ALIGN (rtl));
+		      rtx loc = assign_stack_local
+			(GET_MODE (rtl), GET_MODE_SIZE (GET_MODE (rtl)),
+			 align);
+		      XEXP (rtl, 0) = XEXP (loc, 0);
+		    }
+
 		  SET_DECL_RTL (p, read_complex_part (rtl, false));
 		  SET_DECL_RTL (decl, read_complex_part (rtl, true));
 
@@ -2934,6 +2951,27 @@ assign_parm_setup_block_p (struct assign_parm_data_one *data)
   return false;
 }
 
+/* Return true if FROM_EXPAND is a MEM with an address to be filled in
+   by assign_params.  This should be the case if, and only if,
+   parm_in_stack_slot_p holds for the parm DECL that expanded to
+   FROM_EXPAND, so we check that, too.  */
+
+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)
+	      /* Maybe it was already assigned.  That's ok, especially
+		 for split complex args.  */
+	      || (!result && MEM_P (from_expand)
+		  && (XEXP (from_expand, 0) == virtual_stack_vars_rtx
+		      || (GET_CODE (XEXP (from_expand, 0)) == PLUS
+			  && XEXP (XEXP (from_expand, 0), 0) == virtual_stack_vars_rtx))));
+
+  return result;
+}
+
 /* A subroutine of assign_parms.  Arrange for the parameter to be
    present and valid in DATA->STACK_RTL.  */
 
@@ -2956,8 +2994,7 @@ 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 +3005,7 @@ 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);
@@ -3017,6 +3053,11 @@ assign_parm_setup_block (struct assign_parm_data_all *all,
       else if (size == 0)
 	;
 
+      /* MEM may be a REG if coalescing assigns the param's partition
+	 to a pseudo.  */
+      else if (REG_P (mem))
+	emit_move_insn (mem, entry_parm);
+
       /* If SIZE is that of a mode no bigger than a word, just use
 	 that mode's store operation.  */
       else if (size <= UNITS_PER_WORD)
@@ -3121,7 +3162,7 @@ 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))
@@ -3131,7 +3172,6 @@ assign_parm_setup_reg (struct assign_parm_data_all *all, tree parm,
 	{
 	  gcc_assert (data->passed_pointer);
 	  gcc_assert (GET_CODE (from_expand) == MEM
-		      && GET_MODE (from_expand) == BLKmode
 		      && XEXP (from_expand, 0) == NULL_RTX);
 	  XEXP (from_expand, 0) = parmreg;
 	}
@@ -3349,7 +3389,7 @@ 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 +3495,15 @@ 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));
+	  if (from_expand && !parm_in_unassigned_mem_p (parm, from_expand))
+	    data->stack_parm = from_expand;
 	}
 
       if (data->stack_parm == 0)
@@ -3472,7 +3515,16 @@ 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