re PR tree-optimization/38819 (trapping expression wrongly hoisted out of loop)

2009-01-18  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/38819
	* tree-flow.h (operation_could_trap_helper_p): Declare.
	* tree-eh.c (operation_could_trap_helper_p): Export.
	* tree-ssa-sccvn.h (vn_nary_may_trap): Declare.
	* tree-ssa-sccvn.c (vn_nary_may_trap): New function.
	* tree-ssa-pre.c (insert_into_preds_of_block): Check if we
	are about to insert a possibly trapping instruction and fail
	in this case.

	* gcc.c-torture/execute/pr38819.c: New testcase.

From-SVN: r143485

gcc/ChangeLog

@@ -1,3 +1,14 @@
+2009-01-18  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/38819
+	* tree-flow.h (operation_could_trap_helper_p): Declare.
+	* tree-eh.c (operation_could_trap_helper_p): Export.
+	* tree-ssa-sccvn.h (vn_nary_may_trap): Declare.
+	* tree-ssa-sccvn.c (vn_nary_may_trap): New function.
+	* tree-ssa-pre.c (insert_into_preds_of_block): Check if we
+	are about to insert a possibly trapping instruction and fail
+	in this case.
+
 2009-01-18  Andreas Schwab  <schwab@suse.de>
 
 	* doc/install.texi (Configuration): Remove obsolete paragraph

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2009-01-18  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/38819
+	* gcc.c-torture/execute/pr38819.c: New testcase.
+
 2009-01-17  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/38657

gcc/testsuite/gcc.c-torture/execute/pr38819.c

@@ -0,0 +1,29 @@
+extern void exit (int);
+extern void abort (void);
+
+volatile int a = 1;
+volatile int b = 0;
+volatile int x = 2;
+volatile signed int r = 8;
+
+void __attribute__((noinline))
+foo (void)
+{
+  exit (0);
+}
+
+int
+main (void)
+{
+  int si1 = a;
+  int si2 = b;
+  int i;
+
+  for (i = 0; i < 100; ++i) {
+      foo ();
+      if (x == 8)
+	i++;
+      r += i + si1 % si2;
+  }
+  abort ();
+}

gcc/tree-eh.c

@@ -2067,7 +2067,7 @@ verify_eh_edges (gimple stmt)
 
 /* Helper function for operation_could_trap_p and stmt_could_throw_p.  */
 
-static bool
+bool
 operation_could_trap_helper_p (enum tree_code op,
 			       bool fp_operation,
 			       bool honor_trapv,

gcc/tree-flow.h

@@ -1071,6 +1071,8 @@ static inline bool unmodifiable_var_p (const_tree);
 /* In tree-eh.c  */
 extern void make_eh_edges (gimple);
 extern bool tree_could_trap_p (tree);
+extern bool operation_could_trap_helper_p (enum tree_code, bool, bool, bool,
+					   bool, tree, bool *);
 extern bool operation_could_trap_p (enum tree_code, bool, bool, tree);
 extern bool stmt_could_throw_p (gimple);
 extern bool tree_could_throw_p (tree);

gcc/tree-ssa-pre.c

@@ -3004,6 +3004,15 @@ insert_into_preds_of_block (basic_block block, unsigned int exprnum,
 	}
     }
 
+  /* Make sure we are not inserting trapping expressions.  */
+  FOR_EACH_EDGE (pred, ei, block->preds)
+    {
+      bprime = pred->src;
+      eprime = avail[bprime->index];
+      if (eprime->kind == NARY
+	  && vn_nary_may_trap (PRE_EXPR_NARY (eprime)))
+	return false;
+    }
 
   /* Make the necessary insertions.  */
   FOR_EACH_EDGE (pred, ei, block->preds)

gcc/tree-ssa-sccvn.c

@@ -3072,3 +3072,50 @@ sort_vuses_heap (VEC (tree,heap) *vuses)
 	   sizeof (tree),
 	   operand_build_cmp);
 }
+
+
+/* Return true if the nary operation NARY may trap.  This is a copy
+   of stmt_could_throw_1_p adjusted to the SCCVN IL.  */
+
+bool
+vn_nary_may_trap (vn_nary_op_t nary)
+{
+  tree type;
+  tree rhs2;
+  bool honor_nans = false;
+  bool honor_snans = false;
+  bool fp_operation = false;
+  bool honor_trapv = false;
+  bool handled, ret;
+  unsigned i;
+
+  if (TREE_CODE_CLASS (nary->opcode) == tcc_comparison
+      || TREE_CODE_CLASS (nary->opcode) == tcc_unary
+      || TREE_CODE_CLASS (nary->opcode) == tcc_binary)
+    {
+      type = nary->type;
+      fp_operation = FLOAT_TYPE_P (type);
+      if (fp_operation)
+	{
+	  honor_nans = flag_trapping_math && !flag_finite_math_only;
+	  honor_snans = flag_signaling_nans != 0;
+	}
+      else if (INTEGRAL_TYPE_P (type)
+	       && TYPE_OVERFLOW_TRAPS (type))
+	honor_trapv = true;
+    }
+  rhs2 = nary->op[1];
+  ret = operation_could_trap_helper_p (nary->opcode, fp_operation,
+				       honor_trapv,
+				       honor_nans, honor_snans, rhs2,
+				       &handled);
+  if (handled
+      && ret)
+    return true;
+
+  for (i = 0; i < nary->length; ++i)
+    if (tree_could_trap_p (nary->op[i]))
+      return true;
+
+  return false;
+}

gcc/tree-ssa-sccvn.h

@@ -188,6 +188,7 @@ tree vn_phi_lookup (gimple);
 
 hashval_t vn_nary_op_compute_hash (const vn_nary_op_t);
 int vn_nary_op_eq (const void *, const void *);
+bool vn_nary_may_trap (vn_nary_op_t);
 hashval_t vn_reference_compute_hash (const vn_reference_t);
 int vn_reference_eq (const void *, const void *);
 unsigned int get_max_value_id (void);