tree-optimization/79334 - avoid PRE of possibly trapping array-ref

This replicates tree-eh.c in_array_bound_p into VNs
vn_reference_may_trap to fix hoisting of a possibly trapping
ARRAY_REF across a call that might not return.

2021-08-23  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79334
	* tree-ssa-sccvn.c (copy_reference_ops_from_ref): Record
	a type also for COMPONENT_REFs.
	(vn_reference_may_trap): Check ARRAY_REF with constant index
	against the array domain.

	* gcc.dg/torture/pr79334-0.c: New testcase.
	* gcc.dg/torture/pr79334-1.c: Likewise.

diff --git a/gcc/testsuite/gcc.dg/torture/pr79334-0.c b/gcc/testsuite/gcc.dg/torture/pr79334-0.c
new file mode 100644 (file)
index 0000000..fa45a6d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr79334-0.c
@@ -0,0 +1,23 @@
+/* { dg-do run } */
+/* { dg-additional-sources "pr79334-1.c" } */
+
+extern int d[][8];
+
+static void __attribute__((noinline))
+func_that_exits (int flag)
+{
+  if (!flag)
+    __builtin_exit (0);
+}
+
+int main ()
+{
+  int e = 0;
+  while (1)
+    {
+      func_that_exits (e);
+      /* We do not know whether d[1024][0] will trap.  */
+      e = d[1024][0];
+    }
+  return 0;
+}

diff --git a/gcc/testsuite/gcc.dg/torture/pr79334-1.c b/gcc/testsuite/gcc.dg/torture/pr79334-1.c
new file mode 100644 (file)
index 0000000..b1c8a27
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr79334-1.c
@@ -0,0 +1 @@
+int d[1][8];

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 82bd10bd83c75bb9d2450049e5e0cacdc7c61d22..bf87cee38573064e552ec04e4fc1b3ec37f0cc02 100644 (file)
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -914,9 +914,8 @@ copy_reference_ops_from_ref (tree ref, vec<vn_reference_op_s> *result)
          break;
        case COMPONENT_REF:
          /* The field decl is enough to unambiguously specify the field,
-            a matching type is not necessary and a mismatching type
-            is always a spurious difference.  */
-         temp.type = NULL_TREE;
+            so use its type here.  */
+         temp.type = TREE_TYPE (TREE_OPERAND (ref, 1));
          temp.op0 = TREE_OPERAND (ref, 1);
          temp.op1 = TREE_OPERAND (ref, 2);
          temp.reverse = (AGGREGATE_TYPE_P (TREE_TYPE (TREE_OPERAND (ref, 0)))
@@ -5873,10 +5872,33 @@ vn_reference_may_trap (vn_reference_t ref)
            return true;
          break;
        case ARRAY_RANGE_REF:
-       case ARRAY_REF:
          if (TREE_CODE (op->op0) == SSA_NAME)
            return true;
          break;
+       case ARRAY_REF:
+         {
+           if (TREE_CODE (op->op0) != INTEGER_CST)
+             return true;
+
+           /* !in_array_bounds   */
+           tree domain_type = TYPE_DOMAIN (ref->operands[i+1].type);
+           if (!domain_type)
+             return true;
+
+           tree min = op->op1;
+           tree max = TYPE_MAX_VALUE (domain_type);
+           if (!min
+               || !max
+               || TREE_CODE (min) != INTEGER_CST
+               || TREE_CODE (max) != INTEGER_CST)
+             return true;
+
+           if (tree_int_cst_lt (op->op0, min)
+               || tree_int_cst_lt (max, op->op0))
+             return true;
+
+           break;
+         }
        case MEM_REF:
          /* Nothing interesting in itself, the base is separate.  */
          break;