ipa-cp: Do not create clones for values outside known value range (PR 102513)

PR 102513 shows we emit bogus array access warnings when IPA-CP
creates clones specialized for values which it deduces from arithmetic
jump functions describing self-recursive calls.  Those can however be
avoided if we consult the IPA-VR information that the same pass also
has.

The patch below does that at the stage when normally values are only
examined for profitability.  It would be better not to create lattices
describing such bogus values in the first place, however that presents
an ordering problem, the pass currently propagates all information,
and so both constants and VR, in no particular order when processing
SCCs, and so this approach seemed much simpler.

I plan to rearrange the pass so that it clones in multiple passes over
the call graph (or rather the lattice dependence graph) and it feels
natural to only do propagation for these kinds of recursion in the
second or later passes, which would fix the issue more elegantly.

gcc/ChangeLog:

2022-02-14  Martin Jambor  <mjambor@suse.cz>

	PR ipa/102513
	* ipa-cp.cc (decide_whether_version_node): Skip scalar values
	which do not fit the known value_range.

gcc/testsuite/ChangeLog:

2022-02-14  Martin Jambor  <mjambor@suse.cz>

	PR ipa/102513
	* gcc.dg/ipa/pr102513.c: New test.

diff --git a/gcc/ipa-cp.cc b/gcc/ipa-cp.cc
index 18047c2..8628140 100644 (file)
--- a/gcc/ipa-cp.cc
+++ b/gcc/ipa-cp.cc
@@ -6154,8 +6154,32 @@ decide_whether_version_node (struct cgraph_node *node)
        {
          ipcp_value<tree> *val;
          for (val = lat->values; val; val = val->next)
-           ret |= decide_about_value (node, i, -1, val, &avals,
-                                      &self_gen_clones);
+           {
+             /* If some values generated for self-recursive calls with
+                arithmetic jump functions fall outside of the known
+                value_range for the parameter, we can skip them.  VR interface
+                supports this only for integers now.  */
+             if (TREE_CODE (val->value) == INTEGER_CST
+                 && !plats->m_value_range.bottom_p ()
+                 && !plats->m_value_range.m_vr.contains_p (val->value))
+               {
+                 /* This can happen also if a constant present in the source
+                    code falls outside of the range of parameter's type, so we
+                    cannot assert.  */
+                 if (dump_file && (dump_flags & TDF_DETAILS))
+                   {
+                     fprintf (dump_file, " - skipping%s value ",
+                              val->self_recursion_generated_p ()
+                              ? " self_recursion_generated" : "");
+                     print_ipcp_constant_value (dump_file, val->value);
+                     fprintf (dump_file, " because it is outside known "
+                              "value range.\n");
+                   }
+                 continue;
+               }
+             ret |= decide_about_value (node, i, -1, val, &avals,
+                                        &self_gen_clones);
+           }
        }
 
       if (!plats->aggs_bottom)

diff --git a/gcc/testsuite/gcc.dg/ipa/pr102513.c b/gcc/testsuite/gcc.dg/ipa/pr102513.c
new file mode 100644 (file)
index 0000000..9ee5431
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/pr102513.c
@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -Warray-bounds" } */
+
+extern int block2[7][256];
+
+static int encode_block(int block2[7][256], unsigned level)
+{
+    int best_score = 0;
+
+    for (unsigned x = 0; x < level; x++) {
+        int v = block2[1][x];
+        block2[level][x] = 0;
+        best_score += v * v;
+    }
+
+    if (level > 0 && best_score > 64) {
+        int score = 0;
+
+        score += encode_block(block2, level - 1);
+        score += encode_block(block2, level - 1);
+
+        if (score < best_score) {
+            best_score = score;
+        }
+    }
+
+    return best_score;
+}
+
+int foo(void)
+{
+    return encode_block(block2, 5);
+}