[PATCH][PR65823] Fix va_arg ap_copy nop detection

[Tom de Vries]

Hi,

this patch fixes PR65823.
The problem is a verify_gimple ICE during compilation of 
gcc.c-torture/execute/stdarg-2.c for arm at -O0/-O1:
...
In function 'f3':
src/gcc/testsuite/gcc.c-torture/execute/stdarg-2.c:61:1:
error: incorrect sharing of tree nodes
aps[4]
# .MEM_5 = VDEF <.MEM_11>
aps[4] = aps[4];
...


Before gimplification, f3 looks like this in the original dump:
...
  struct va_list aps[10];

    struct va_list aps[10];
  __builtin_va_start ((struct  &) (struct  *) &aps[4], i);
  x = VA_ARG_EXPR <aps[4]>;
  __builtin_va_end ((struct  &) (struct  *) &aps[4]);
...

After gimplification, it looks like:
...
f3 (int i)
{
  long intD.5 x.0D.4231;
  struct va_listD.4222 apsD.4227[10];

  try
    {
      # USE = anything
      # CLB = anything
      __builtin_va_startD.1052 (&apsD.4227[4], 0);
      # USE = anything
      # CLB = anything
      x.0D.4231 = VA_ARG (&apsD.4227[4], 0B);
      apsD.4227[4] = apsD.4227[4];
      xD.4223 = x.0D.4231;
      # USE = anything
      # CLB = anything
      __builtin_va_endD.1051 (&apsD.4227[4]);
    }
  finally
    {
      apsD.4227 = {CLOBBER};
    }
}
...

The nop 'apsD.4227[4] = apsD.4227[4]' introduced during gimplification is not 
meant to be there.


There is already a test 'TREE_OPERAND (ap, 0) != TREE_OPERAND (ap_copy, 0))' in 
gimplify_modify_expr to prevent this nop:
...
  /* When gimplifying the &ap argument of va_arg, we might end up with
       ap.1 = ap
       va_arg (&ap.1, 0B)
     We need to assign ap.1 back to ap, otherwise va_arg has no effect on
     ap.  */
  if (ap != NULL_TREE
      && TREE_CODE (ap) == ADDR_EXPR
      && TREE_CODE (ap_copy) == ADDR_EXPR
      && TREE_OPERAND (ap, 0) != TREE_OPERAND (ap_copy, 0))
    gimplify_assign (TREE_OPERAND (ap, 0), TREE_OPERAND (ap_copy, 0), pre_p);
...

But the test is a pointer equality test, and it fails in this case.

The patches fixes the problem by using operand_equal_p to do the equality test.


Bootstrapped and reg-tested on x86_64.

Did minimal non-bootstrap build on arm and reg-tested.

OK for trunk?

Thanks,
- Tom
Fix va_arg ap_copy nop detection

2015-04-22  Tom de Vries  <t...@codesourcery.com>

	PR tree-optimization/65823
	* gimplify.c (gimplify_modify_expr): Use operand_equal_p to test for
	equality between ap_copy and ap.
---
 gcc/gimplify.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 0a8ef84..c68bd47 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -4792,7 +4792,7 @@ gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
   if (ap != NULL_TREE
       && TREE_CODE (ap) == ADDR_EXPR
       && TREE_CODE (ap_copy) == ADDR_EXPR
-      && TREE_OPERAND (ap, 0) != TREE_OPERAND (ap_copy, 0))
+      && !operand_equal_p (TREE_OPERAND (ap, 0), TREE_OPERAND (ap_copy, 0), 0))
     gimplify_assign (TREE_OPERAND (ap, 0), TREE_OPERAND (ap_copy, 0), pre_p);
 
   if (want_value)
-- 
1.9.1