[Bug tree-optimization/57742] memset(malloc(n),0,n) -> calloc(n,1)

["glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57742

--- Comment #21 from Marc Glisse <glisse at gcc dot gnu.org> ---
I am testing the following:

--- tree-ssa-strlen.c    (revision 211967)
+++ tree-ssa-strlen.c    (working copy)
@@ -1646,20 +1646,22 @@ handle_builtin_memset (gimple_stmt_itera
   enum built_in_function code1 = DECL_FUNCTION_CODE (callee1);
   tree size = gimple_call_arg (stmt2, 2);
   if (code1 == BUILT_IN_CALLOC)
     /* Not touching stmt1 */ ;
   else if (code1 == BUILT_IN_MALLOC
        && operand_equal_p (gimple_call_arg (stmt1, 0), size, 0))
     {
       gimple_stmt_iterator gsi1 = gsi_for_stmt (stmt1);
       update_gimple_call (&gsi1, builtin_decl_implicit (BUILT_IN_CALLOC), 2,
               size, build_one_cst (size_type_node));
+      si1->length = build_int_cst (size_type_node, 0);
+      si1->stmt = gsi_stmt (gsi1);
     }
   else
     return true;
   tree lhs = gimple_call_lhs (stmt2);
   unlink_stmt_vdef (stmt2);
   if (lhs)
     {
       gimple assign = gimple_build_assign (lhs, ptr);
       gsi_replace (gsi, assign, false);
     }