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.

3 files changed, 50 insertions, 4 deletions

diff --git a/gcc/testsuite/gcc.dg/torture/pr79334-0.c b/gcc/testsuite/gcc.dg/torture/pr79334-0.c
new file mode 100644
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
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 82bd10b..bf87cee 100644
--- 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;