PR middle-end/81908 - FAIL: gfortran.dg/alloc_comp_auto_array_2.f90 -O3 -g -m32

gcc/ChangeLog:

	PR middle-end/81908
	* gimple-fold.c (size_must_be_zero_p): New function.
	(gimple_fold_builtin_memory_op): Call it.

gcc/testsuite/ChangeLog:

	PR middle-end/81908
	* gcc.dg/tree-ssa/builtins-folding-gimple-2.c: New test.
	* gcc.dg/tree-ssa/builtins-folding-gimple-3.c: New test.
	* gcc.dg/tree-ssa/pr81908.c: New test.

From-SVN: r251347

1 files changed, 33 insertions, 2 deletions

diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 251446c..bf39f28 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -628,6 +628,36 @@ var_decl_component_p (tree var)
   return SSA_VAR_P (inner);
 }
 
+/* If the SIZE argument representing the size of an object is in a range
+   of values of which exactly one is valid (and that is zero), return
+   true, otherwise false.  */
+
+static bool
+size_must_be_zero_p (tree size)
+{
+  if (integer_zerop (size))
+    return true;
+
+  if (TREE_CODE (size) != SSA_NAME)
+    return false;
+
+  wide_int min, max;
+  enum value_range_type rtype = get_range_info (size, &min, &max);
+  if (rtype != VR_ANTI_RANGE)
+    return false;
+
+  tree type = TREE_TYPE (size);
+  int prec = TYPE_PRECISION (type);
+
+  wide_int wone = wi::one (prec);
+
+  /* Compute the value of SSIZE_MAX, the largest positive value that
+     can be stored in ssize_t, the signed counterpart of size_t.  */
+  wide_int ssize_max = wi::lshift (wi::one (prec), prec - 1) - 1;
+
+  return wi::eq_p (min, wone) && wi::geu_p (max, ssize_max);
+}
+
 /* Fold function call to builtin mem{{,p}cpy,move}.  Return
    false if no simplification can be made.
    If ENDP is 0, return DEST (like memcpy).
@@ -646,8 +676,9 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
   tree destvar, srcvar;
   location_t loc = gimple_location (stmt);
 
-  /* If the LEN parameter is zero, return DEST.  */
-  if (integer_zerop (len))
+  /* If the LEN parameter is a constant zero or in range where
+     the only valid value is zero, return DEST.  */
+  if (size_must_be_zero_p (len))
     {
       gimple *repl;
       if (gimple_call_lhs (stmt))