middle-end/111422 - wrong stack var coalescing, handle PHIs

The gcc.c-torture/execute/pr111422.c testcase after installing the
sink pass improvement reveals that we also need to handle

 _65 = &g + _58;              _44 = &g + _43;
 # _59 = PHI <_65, _44>
 *_59 = 8;
 g = {v} {CLOBBER(eos)};
 ...
 n[0] = &f;
 *_59 = 8;
 g = {v} {CLOBBER(eos)};

where we fail to see the conflict between n and g after the first
clobber of g.  Before the sinking improvement there was a conflict
recorded on a path where _65/_44 are unused, so the real conflict
was missed but the fake one avoided the miscompile.

The following handles PHI defs in add_scope_conflicts_2 which
fixes the issue.

	PR middle-end/111422
	* cfgexpand.cc (add_scope_conflicts_2): Handle PHIs
	by recursing to their arguments.

1 files changed, 15 insertions, 4 deletions

diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
index 557cb28..8de5f2b 100644
--- a/gcc/cfgexpand.cc
+++ b/gcc/cfgexpand.cc
@@ -584,10 +584,21 @@ add_scope_conflicts_2 (tree use, bitmap work,
 	  || INTEGRAL_TYPE_P (TREE_TYPE (use))))
     {
       gimple *g = SSA_NAME_DEF_STMT (use);
-      if (is_gimple_assign (g))
-	if (tree op = gimple_assign_rhs1 (g))
-	  if (TREE_CODE (op) == ADDR_EXPR)
-	    visit (g, TREE_OPERAND (op, 0), op, work);
+      if (gassign *a = dyn_cast <gassign *> (g))
+	{
+	  if (tree op = gimple_assign_rhs1 (a))
+	    if (TREE_CODE (op) == ADDR_EXPR)
+	      visit (a, TREE_OPERAND (op, 0), op, work);
+	}
+      else if (gphi *p = dyn_cast <gphi *> (g))
+	for (unsigned i = 0; i < gimple_phi_num_args (p); ++i)
+	  if (TREE_CODE (use = gimple_phi_arg_def (p, i)) == SSA_NAME)
+	    if (gassign *a = dyn_cast <gassign *> (SSA_NAME_DEF_STMT (use)))
+	      {
+		if (tree op = gimple_assign_rhs1 (a))
+		  if (TREE_CODE (op) == ADDR_EXPR)
+		    visit (a, TREE_OPERAND (op, 0), op, work);
+	      }
     }
 }