Re: [vta, graphite?] propagate degenerate phi nodes into debug stmts

[Alexandre Oliva <aoliva@redhat.com>]

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According to http://gcc.gnu.org/ml/gcc-patches/2009-11/msg00999.html
on Nov 19, 2009, Richard Guenther <richard.guenther@gmail.com> wrote:

> On Thu, Nov 19, 2009 at 4:05 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
>> On Nov 17, 2009, Richard Guenther <richard.guenther@gmail.com> wrote:
>> 
>>>>> This looks odd.  SSA DEF operand iteration should walk the PHI defs
>>>>> as well, so the change should not be necessary.
>> 
>>>> I thought so, too, but by the time we get there, the operands of the PHI
>>>> stmt have already been disconnected.
>> 
>>> It shouldn't be.  Please try to figure out why instead.
>> 
>> Gotta use a different FOR_EACH macro to handle PHI nodes.
>> 
>> s/FOR_EACH_SSA_DEF_OPERAND/FOR_EACH_PHI_OR_STMT_DEF/ fixed it.
>> 
>> In order to make sure no other such mistakes had been made in GCC, I
>> added an assertion check in the iterator initializer and adjusted the
>> uses of GIMPLE_PHI nodes that triggered the assertion, but that would
>> have done nothing whatsoever in its absence.  I haven't looked into
>> whether doing nothing is correct.
>> 
>> Should I check this in?

> I think we should rather let num_ssa_operands and delink_stmt_imm_use
> ICE on PHIs, but I'd rather do this in stage1 - can you queue this
> patch until then?

You meant 4.6 stage1, but I missed it.  How's it for 4.7 stage1?
Regstrapped on x86_64-linux-gnu and i686-linux-gnu.


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for  gcc/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* tree-flow-inline.h (op_iter_init): Reject GIMPLE_PHI stmts.
	(num_ssa_operands): Skip GIMPLE_PHI.
	(delink_stmt_imm_use): Likewise.

Index: gcc/tree-flow-inline.h
===================================================================
--- gcc/tree-flow-inline.h.orig	2010-06-10 07:20:02.000000000 -0300
+++ gcc/tree-flow-inline.h	2010-06-10 15:17:51.000000000 -0300
@@ -716,9 +716,11 @@ clear_and_done_ssa_iter (ssa_op_iter *pt
 static inline void
 op_iter_init (ssa_op_iter *ptr, gimple stmt, int flags)
 {
-  /* We do not support iterating over virtual defs or uses without
+  /* PHI nodes require a different iterator initialization path.  We
+     do not support iterating over virtual defs or uses without
      iterating over defs or uses at the same time.  */
-  gcc_checking_assert ((!(flags & SSA_OP_VDEF) || (flags & SSA_OP_DEF))
+  gcc_checking_assert (gimple_code (stmt) != GIMPLE_PHI
+		       && (!(flags & SSA_OP_VDEF) || (flags & SSA_OP_DEF))
 		       && (!(flags & SSA_OP_VUSE) || (flags & SSA_OP_USE)));
   ptr->defs = (flags & (SSA_OP_DEF|SSA_OP_VDEF)) ? gimple_def_ops (stmt) : NULL;
   if (!(flags & SSA_OP_VDEF)
@@ -847,8 +849,9 @@ num_ssa_operands (gimple stmt, int flags
   tree t;
   int num = 0;
 
-  FOR_EACH_SSA_TREE_OPERAND (t, stmt, iter, flags)
-    num++;
+  if (gimple_code (stmt) != GIMPLE_PHI)
+    FOR_EACH_SSA_TREE_OPERAND (t, stmt, iter, flags)
+      num++;
   return num;
 }
 
@@ -860,7 +863,8 @@ delink_stmt_imm_use (gimple stmt)
    ssa_op_iter iter;
    use_operand_p use_p;
 
-   if (ssa_operands_active ())
+   if (ssa_operands_active ()
+       && gimple_code (stmt) != GIMPLE_PHI)
      FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
        delink_imm_use (use_p);
 }

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-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
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Free Software Evangelist      Red Hat Brazil Compiler Engineer