[gcc r15-517] middle-end/111422 - wrong stack var coalescing, handle PHIs

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:ab25eef36400e8c1d28e3ed059c5f95a38b45f17

commit r15-517-gab25eef36400e8c1d28e3ed059c5f95a38b45f17
Author: Richard Biener <rguent...@suse.de>
Date:   Wed May 15 13:06:30 2024 +0200

    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.

Diff:
---
 gcc/cfgexpand.cc | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
index 557cb28733bd..8de5f2ba58b7 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);
+             }
     }
 }