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

[Richard Biener]

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.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

OK if that succeeds?

Thanks,
Richard.

        PR middle-end/111422
        * cfgexpand.cc (add_scope_conflicts_2): Handle PHIs
        by recursing to their arguments.
---
 gcc/cfgexpand.cc | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
index 557cb28733b..e4d763fa998 100644
--- a/gcc/cfgexpand.cc
+++ b/gcc/cfgexpand.cc
@@ -584,10 +584,23 @@ 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);
+               }
+       }
     }
 }
 
-- 
2.35.3