cfgexpand: Workaround CSE of ADDR_EXPRs in VAR_DECL partitioning [PR113372]

The following patch adds a quick workaround to bugs in VAR_DECL
partitioning.
The problem is that there is no dependency between ADDR_EXPRs of local
decls and CLOBBERs of those vars, so VN can CSE uses of ADDR_EXPRs
(including ivopts integral variants thereof), which can break
add_scope_conflicts discovery of what variables are actually used
in certain region.
E.g. we can have
  ivtmp.40_3 = (unsigned long) &MEM <unsigned long[100]> [(void *)&bitint.6 + 8B];
...
  uses of ivtmp.40_3
...
  bitint.6 ={v} {CLOBBER(eos)};
...
  ivtmp.28_43 = (unsigned long) &MEM <unsigned long[100]> [(void *)&bitint.6 + 8B];
...
  uses of ivtmp.28_43
before VN (such as dom3), which the add_scope_conflicts code identifies as 2
independent uses of bitint.6 variable (which is correct), but then VN
determines ivtmp.28_43 is the same as ivtmp.40_3 and just uses ivtmp.40_3
even in the second region; at that point add_scope_conflict thinks the
bitint.6 variable is not used in that region anymore.

The following patch does a simple single def-stmt check for such ADDR_EXPRs
(rather than say trying to do a full propagation of what SSA_NAMEs can
contain ADDR_EXPRs of local variables), which seems to workaround all 4 PRs.

In addition to this patch I've used the attached one to gather statistics
on the total size of all variable partitions in a function and seems besides
the new testcases nothing is really affected compared to no patch (I've
actually just modified the patch to == OMP_SCAN instead of == ADDR_EXPR, so
it looks the same except that it never triggers).  The comparison wasn't
perfect because I've only gathered BITS_PER_WORD, main_input_filename (did
some replacement of build directories and /tmp/ccXXXXXX names of LTO to make
it more similar between the two bootstraps/regtests), current_function_name
and the total size of all variable partitions if any, because I didn't
record e.g. the optimization options and so e.g. torture tests which iterate
over options could have different partition sizes even in one compiler when
BITS_PER_WORD, main_input_filename and current_function_name are all equal.
So had to write an awk script to check if the first triple in the second
build appeared in the first one and the quadruple in the second build
appeared in the first one too, otherwise print result and that only
triggered in the new tests.
Also, the cc1plus binary according to objdump -dr is identical between the
two builds except for the ADDR_EXPR vs. OMP_SCAN constant in the two spots.

2024-01-16  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113372
	PR middle-end/90348
	PR middle-end/110115
	PR middle-end/111422
	* cfgexpand.cc (add_scope_conflicts_2): New function.
	(add_scope_conflicts_1): Use it.

	* gcc.c-torture/execute/pr90348.c: New test.
	* gcc.c-torture/execute/pr110115.c: New test.
	* gcc.c-torture/execute/pr111422.c: New test.

(cherry picked from commit 1251d3957de04dc9b023a23c09400217e13deadb)

4 files changed, 150 insertions, 2 deletions

diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
index 9c4d67b..eadec9a 100644
--- a/gcc/cfgexpand.cc
+++ b/gcc/cfgexpand.cc
@@ -571,6 +571,26 @@ visit_conflict (gimple *, tree op, tree, void *data)
   return false;
 }
 
+/* Helper function for add_scope_conflicts_1.  For USE on
+   a stmt, if it is a SSA_NAME and in its SSA_NAME_DEF_STMT is known to be
+   based on some ADDR_EXPR, invoke VISIT on that ADDR_EXPR.  */
+
+static inline void
+add_scope_conflicts_2 (tree use, bitmap work,
+		       walk_stmt_load_store_addr_fn visit)
+{
+  if (TREE_CODE (use) == SSA_NAME
+      && (POINTER_TYPE_P (TREE_TYPE (use))
+	  || 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);
+    }
+}
+
 /* Helper routine for add_scope_conflicts, calculating the active partitions
    at the end of BB, leaving the result in WORK.  We're called to generate
    conflicts when FOR_CONFLICT is true, otherwise we're just tracking
@@ -583,6 +603,8 @@ add_scope_conflicts_1 (basic_block bb, bitmap work, bool for_conflict)
   edge_iterator ei;
   gimple_stmt_iterator gsi;
   walk_stmt_load_store_addr_fn visit;
+  use_operand_p use_p;
+  ssa_op_iter iter;
 
   bitmap_clear (work);
   FOR_EACH_EDGE (e, ei, bb->preds)
@@ -593,7 +615,10 @@ add_scope_conflicts_1 (basic_block bb, bitmap work, bool for_conflict)
   for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
     {
       gimple *stmt = gsi_stmt (gsi);
+      gphi *phi = as_a <gphi *> (stmt);
       walk_stmt_load_store_addr_ops (stmt, work, NULL, NULL, visit);
+      FOR_EACH_PHI_ARG (use_p, phi, iter, SSA_OP_USE)
+	add_scope_conflicts_2 (USE_FROM_PTR (use_p), work, visit);
     }
   for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); gsi_next (&gsi))
     {
@@ -613,8 +638,7 @@ add_scope_conflicts_1 (basic_block bb, bitmap work, bool for_conflict)
 	}
       else if (!is_gimple_debug (stmt))
 	{
-	  if (for_conflict
-	      && visit == visit_op)
+	  if (for_conflict && visit == visit_op)
 	    {
 	      /* If this is the first real instruction in this BB we need
 	         to add conflicts for everything live at this point now.
@@ -634,6 +658,8 @@ add_scope_conflicts_1 (basic_block bb, bitmap work, bool for_conflict)
 	      visit = visit_conflict;
 	    }
 	  walk_stmt_load_store_addr_ops (stmt, work, visit, visit, visit);
+	  FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
+	    add_scope_conflicts_2 (USE_FROM_PTR (use_p), work, visit);
 	}
     }
 }
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr110115.c b/gcc/testsuite/gcc.c-torture/execute/pr110115.c
new file mode 100644
index 0000000..02dec54
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr110115.c
@@ -0,0 +1,45 @@
+/* PR middle-end/110115 */
+
+int a;
+signed char b;
+
+static int
+foo (signed char *e, int f)
+{
+  int d;
+  for (d = 0; d < f; d++)
+    e[d] = 0;
+  return d;
+}
+
+int
+bar (signed char e, int f)
+{
+  signed char h[20];
+  int i = foo (h, f);
+  return i;
+}
+
+int
+baz ()
+{
+  switch (a)
+    {
+    case 'f':
+      return 0;
+    default:
+      return ~0;
+    }
+}
+
+int
+main ()
+{
+  {
+    signed char *k[3];
+    int d;
+    for (d = 0; bar (8, 15) - 15 + d < 1; d++)
+      k[baz () + 1] = &b;
+    *k[0] = -*k[0];
+  }
+}
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr111422.c b/gcc/testsuite/gcc.c-torture/execute/pr111422.c
new file mode 100644
index 0000000..f5920dd
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr111422.c
@@ -0,0 +1,39 @@
+/* PR middle-end/111422 */
+
+int a, b;
+int *c = &b;
+unsigned d;
+signed char e;
+int f = 1;
+
+int
+foo (int k, signed char *l)
+{
+  if (k < 6)
+    return a;
+  l[0] = l[1] = l[k - 1] = 8;
+  return 0;
+}
+
+int
+bar (int k)
+{
+  signed char g[11];
+  int h = foo (k, g);
+  return h;
+}
+
+int
+main ()
+{
+  for (; b < 8; b = b + 1)
+    ;
+  int j;
+  int *n[8];
+  for (j = 0; 18446744073709551608ULL + bar (*c) + *c + j < 2; j++)
+    n[j] = &f;
+  for (; e <= 4; e++)
+    d = *n[0] == f;
+  if (d != 1)
+    __builtin_abort ();
+}
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr90348.c b/gcc/testsuite/gcc.c-torture/execute/pr90348.c
new file mode 100644
index 0000000..341cedd
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr90348.c
@@ -0,0 +1,38 @@
+/* PR middle-end/90348 */
+
+void __attribute__ ((noipa))
+set_one (unsigned char *ptr)
+{
+  *ptr = 1;
+}
+
+void __attribute__ ((noipa))
+check_zero (unsigned char const *in, unsigned int len)
+{
+  for (unsigned int i = 0; i < len; ++i)
+    if (in[i] != 0)
+      __builtin_abort ();
+}
+
+static void
+set_one_on_stack (void)
+{
+  unsigned char buf[1];
+  set_one (buf);
+}
+
+int
+main ()
+{
+  for (int i = 0; i <= 4; ++i)
+    {
+      unsigned char in[4];
+      for (int j = 0; j < i; ++j)
+	{
+	  in[j] = 0;
+	  set_one_on_stack ();
+	}
+      check_zero (in, i);
+    }
+  return 0;
+}